Üú  GLTMP˜˜GLTMP.DBV0ÖsVÿÿqpCC]@ Bq€—ª”I ®Hrá Vÿÿÿìp!DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD*A 1.2 MB floppy is a magnetic diskette for storing and retrieving electronic data and programs. It was introduced by IBM with the AT-class machine. It is 5.25" in diameter, the same physical size as its predecessor, the 360 K floppy, but can store more than three times the capacity. The 1.2 MB floppies are referred to as high capacity or high density diskettes. A 1.2 MB floppy diskette, that has been formatted with a 1.2 MB drive, cannot be read or properly written to with a 360 K floppy disk drive. Because the two disk drives appear to be identical, this is often a confusing matter for beginners. The 1.2 MB floppy disk drives, however, can also read and write 360 K floppies. Generally, a PC or XT-class machine will have a 360 K floppy drive while an AT-class machine will house a 1.2 MB floppy drive. ¨A 1.44 MB microdiskette is a magnetic diskette for storing and retrieving electronic data and programs. The 1.44 MB microdiskette was introduced in the late 1980's as a high density 3.5" diskette. It has a data storage capacity of 1.44 megabytes. A 1.44 MB microdiskette, that has been formatted with a 1.44 MB high density drive, cannot be read or reliably written to with a 720 K diskette drive. Because the two disk drives and diskettes appear to be identical, this is often a confusing matter for beginners. The 1.44 MB microdiskette drives, however, can also read and write 720 K diskettes. See the table "Floppy Disk Specifications" for an overview. TZ10Base-T is the communication standard approved in September of 1990 by the IEEE. 10Base-T, or 802.3i, is the standard for running 10 megabits per second Ethernet LANs over unshielded twisted-pair wiring (UTP), common telephone wire. It is based on a star topology, where all communication goes through a central point, the LAN's hub. Thus, network management tools can be used to monitor and control network resources in ways that are impossible with bus topologies. 10Base-2 refers to the IEEE standard for Thin Ethernet which is also referred to as CheaperNet or CNet. It uses an RG58 coax cable up to 200 meters in length for a single trunk segment. 10Base-5 refers to the IEEE standard for Thick Ethernet which is also referred to as ENet. It uses an RG11 coax cable up to 500 meters in length for a single trunk segment. EfIntroduced by Toshiba at the 1989 Spring Comdex, the 2.88 megabyte drive doubles the amount of data storage available on the existing high density 3.5" microdiskettes. The unformatted, blank capacity is rated at 4.0 megabytes. The additional data storage is accomplished by doubling the number of sectors per track, from 18 to 36, or packing twice as many bits on each track. This is achieved by recording the data up and down (perpendicularly) rather than end to end along the track. Toshiba's new proposed standard does not increase either the number of tracks on the disk or the track density. Although this allows existing head-positioning assemblies to be used, a 2.88 drive will need a new head, supporting electronics, and a modified controller. See the table "Floppy Disk Specifications" for an overview. Introduced in 1986 by Sony Corporation, the 3.5" disk, often called a microdiskette, is used for data storage on personal computers. It provides significant design improvements over the conventional 5.25" floppy diskette. The smaller size and stronger container make handling easier and safer. The actual magnetic disk surface is only exposed when the disk is inserted in the drive. This reduces the possibility of contamination by fingerprints and dust particles. ÚÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄ¿ ³ Storage ³ No. ³ No. ³ Sectors ³ Sector ³ Cluster ³ MS-DOS ³ ³ Capacity ³ Heads ³ Tracks ³ /Track ³ Size ³ Size ³ Version ³ ÃÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄ´ ³ 720 K ³ 2 ³ 80 ³ 9 ³ 512 ³ 1024 ³ 3.2+ ³ ³ 1.44 MB ³ 2 ³ 80 ³ 18 ³ 512 ³ 512 ³ 3.3+ ³ ³ 2.88 MB ³ 2 ³ 80 ³ 36 ³ 512 ³ 512 ³ 3.3+ ³ ÀÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÙ òWith versions of DOS prior to 4.0 there is a built-in limit on the size of a disk partition. It's just a matter of arithmetic. Using the original design parameters of DOS, we can show how the maximum size disk partition is defined. The facts: One word, 16 bits, is defined for DOS to access sectors within its hard disk partition. A single 16-bit binary word can represent values from zero through 65,535. This limits the partition's total sector count to 65,536. Hard disk sectors are 512 bytes long. Now the arithmetic: 512 bytes times 65,536 sectors = 33,554,432 And since there are 1,048,576 bytes in each megabyte, the maximum size partition calculates to exactly 32 megabytes. ×A 360 K floppy is a magnetic diskette for storing and retrieving electronic data and programs. The 360 K floppy diskettes were introduced by IBM with the original PC class machine. It has a data storage capacity of 360 kilobytes. It is 5.25" in diameter. A 360 K floppy diskette can be read and written to both with a 360 K drive and with the later model, high density 1.2 MB floppy disk drives. Because the two disk drives and the diskettes appear to be identical, this is often a confusing matter for beginners. Generally, a PC or XT-class machine will have a 360 K floppy drive while an AT-class machine will house a 1.2 MB floppy drive. See the table "Floppy Disk Specifications" for an overview. ãFA 4GL, Fourth Generation Language, refers to the most recent level of programming languages whereby programs are written that consist of commands from the application package which is written in a second or third generation language. dBase programs, Query languages, and report writers are good examples of 4GL programs. Although the terms 1GL, 2GL, and 3GL are rarely used, 1GL refers to machine language programming, the lowest level computer language. 2GL refers to assembly language programming, and 3GL then refers to all the third generation programming languages such as BASIC, COBOL, FORTRAN, Pascal, C, Ada, etc. where the source code is compiled to create an executable program file or application package. 4QIn the late 1970's when microcomputers first appeared, the only means of storing programs and data off-line was on 5.25" floppy diskettes. Hard disk drives had not yet been invented. The original 5.25" disk drives were about three inches in height and were housed in the computer in one of two bays. ÚÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄ¿ ³ Storage ³ No. ³ No. ³ Sectors ³ Sector ³ Cluster ³ DOS ³ ³ Capacity ³ Heads ³ Tracks ³ /Track ³ Size ³ Size ³ Version ³ ÃÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄ´ ³ 160 K ³ 1 ³ 40 ³ 8 ³ 512 ³ 512 ³ ALL ³ ³ 180 K ³ 1 ³ 40 ³ 9 ³ 512 ³ 1024 ³ 2.0+ ³ ³ 320 K ³ 2 ³ 40 ³ 8 ³ 512 ³ 1024 ³ 1.1+ ³ ³ 360 K ³ 2 ³ 40 ³ 9 ³ 512 ³ 1024 ³ 2.0+ ³ ³ 1.2 MB ³ 2 ³ 80 ³ 15 ³ 512 ³ 512 ³ 3.0+ ³ ÀÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÙ Only the 360K and 1.2 MB (5.25") floppies are in common use today. "pThe first-generation microcomputers utilizing the Intel 8088 or 8086 microprocessor chip were designed to address or manipulate 1,024 kilobytes of random access memory (RAM). The designers figured that the lower 640 kilobytes of that 1,024K would be sufficient memory for DOS and its applications. So that's the way it was set-up. In the early to mid-1980's, when these systems began to proliferate, most of them operated with only 256K or 512K of memory (RAM), and the software applications then would execute with memory to spare. By the late 1980's, systems were rarely sold with less than 640K of memory because the faster and more powerful programs had grown in size. Many interesting "work-arounds" have been designed to extend and/or expand memory beyond the 640K barrier. 6A 720 K microdiskette is a magnetic diskette for storing and retrieving electronic data and programs. The 720 K microdiskette was introduced in the mid 1980's as a 3.5" diskette. It has a data storage capacity of 720 Kilobytes. A 720 K microdiskette can be read and written to both with a 720 K drive and with the later model, high density 1.44 MB floppy disk drives. Because the two disk drives and the diskettes appear to be identical, this is often a confusing matter for beginners. See the table "Floppy Disk Specifications" for an overview. The 8514/A is an analog video display adapter from IBM for the PS/2 line of personal computers. Compared to previous display adapters such as EGA and VGA, it provides a high resolution of 1024x768 pixels with up to 256 colors or 64 shades of gray. It is an interlaced monitor which means that it scans every other line each time the screen is refreshed. It provides a video co-processor that performs two dimensional graphics functions internally, thus relieving the CPU of graphics tasks. The 8514/A monitor improves the performance of CAD applications by as much as ten times. The IBM 8514 display system is a combination of the 16-inch multiple-fixed-frequency 8514 monitor and the 8514/A graphics adapter. They work together only in MCA systems. p6A 9-Track tape is a reel of half-inch magnetic tape for storing computer data. 9-Track tape reels are about 12 inches in diameter and are widely used with mainframe and minicomputers. They are available in a variety of tape lengths, such as 1200, 2400, and 3600 foot reels. Depending on the capabilities of the tape drive, the data can be recorded on the tape at 800 bytes per inch (800 BPI), or 1600 bytes per inch (1600 BPI). The recording scheme places data on nine separate parallel tracks, the 8 data bits of a byte plus 1 parity bit. Early magnetic tapes used a 7-Track recording scheme at 556 BPI. OAn A/B switch is a hardware device that provides a junction in an electrical cable so that the signals can be sent along one of two paths. This device is frequently used when two printers are connected to one computer port. The operator can change the switch setting from "A" to "B" depending on which printer is to be used. @XWhen the execution of a program or task is terminated because of an abnormal end or when the task is terminated by the operator before its completion, the program is said to have been aborted. Control is then returned to the operating system. The term 'abend' (abnormal end) is sometimes used in place of abort. ÓzAn access code or a password is simply an identification number or a set of characters that are sometimes required to gain entry to a computer program or system. It is often desirable for individuals and companies to protect their valuable data or resources from unauthorized use. However, the computer has no way of knowing whether the person entering the password or code is legitimate or not, so always protect your passwords and change them often. çRThe time required for a memory device to produce a dependable output signal after it receives an input signal requesting the contents at an address is called its access time. To take full advantage of the central processor's potential speed, the memory chips should have access times fast enough to function properly at the processor's optimal speed. The access time for a storage device such as a disk is the amount of time required to begin delivering data after the CPU sends a data request. Since different operating environments can affect access times, the figure given is usually an average time. Benchmark tests will often measure a system's access times. See the reference table: "Microprocessor Clock Rates" ”pAn acronym is a word formed from the first or first few letters of a series of words. The following examples of acronyms are further discussed in this PC-GLOSSARY program: MODEM, from MOdulator-DEModulator COBOL, from COmmon Business Oriented Language FORTRAN, from FORmula TRANslator WORM, from Write Once Read Many NetBIOS, from Network Basic Input/Output System CA hub is a distribution, hardware device used in certain network topologies to perform special functions with the transmission signals. There are two types of network hubs, active and passive. An active hub is used to amplify and condition the transmission signals while allowing for additional workstation ports to be added. Active hubs have between four and 64 ports. A passive hub, often with just 4 ports, is also used to split a transmission signal so that additional workstations can be added, but a passive hub cannot amplify the signal. Passive hubs must therefore be connected directly to a workstation or an active hub. Local Area Networks using ARCnet topology have active and passive hubs attached to achieve a maximum cabling distance of 20,000 feet from any node on the network to any other node. oiThe dictionary defines ad hoc as Latin for 'to this', or for this specific purpose; for a special case only. An ad hoc query is a request or an inquiry for information to be extracted from a database. It is initiated directly by a user, rather than indirectly through an application program that provides menus or other structures for formulating the query. ˜Ada is a high-level programming language developed in the late 1970's for the U.S. Department of Defense. It is intended particularly for embedded systems and stresses modularity, reliability, and maintainability. It bears a strong resemblance to Pascal and was designed to improve programmer productivity by allowing several tasks to be performed simultaneously. It is very large and comprehensive. Ada is named after Augusta Ada Byron, the Countess of LoveLace, who is credited as being the first computer programmer. In the mid-nineteenth century, she translated the description of Charles Babbage's Analytical Engine into French. During the translation she took many notes and wrote a series of instructions for the machine to perform complex mathematical calculations. NOTE: There are Ada compilers for the IBM-compatible PCs. See the October '89 issue of Embedded Systems Programming &7In a network of computers, a routing technique that has the capability of changing or re-defining a route while the transmission of data is in progress is called adaptive or dynamic routing. The route is typically modified in response to traffic congestion or a hardware device failure. "Each location in computer memory is numbered consecutively. The number is referred to as the location's address. An address can be a label, name, or number that identifies a particular register, an exact storage location in main memory, or an external storage device. After a computer program is written and compiled or assembled into machine language, it can be loaded into the computer's memory where it references actual addresses. In another sense, each workstation or node in a network of computers has a unique address. }@"AI" is the field of computer science that seeks to understand and implement computer-based technology that can simulate the characteristics of human intelligence. A common goal of artificial intelligence work involves developing computer programs capable of learning from experience in order to solve problems. "AI" refers to the development or capability of a machine that can proceed or perform functions that are normally concerned with human intelligence, such as learning, adapting, reasoning, self-correction, and automatic improvement. In a more restricted sense, artificial intelligence refers to the study of techniques for the more effective use of digital computers by improved programming practices. PROLOG and Lisp are the most popular programming languages for the development of non-numeric programs, particularly in the field of Artificial Intelligence. *jAn acronym for ALGOrithmic Language, ALGOL is an international high-level programming language used to code mathematical problems. Originally developed in 1958 as a means of communicating theories and concepts, it was not implemented until 1960 as ALGOL-60. The last standard version of the language, ALGOL-68, corrected many of its earlier deficiencies. ALGOL was popular in Europe. Although it is essentially a "dead" language, ALGOL has had a strong impact on program language design and managed to spawn others, most notably Pascal. ›An algorithm is a formal procedure that always produces a correct or optimal result. It applies a step-by-step procedure that guarantees a specific outcome or solves a specific problem. It is a predetermined set of instructions for solving a specific mathematical problem in a finite number of steps. Devising algorithms and proving their correctness is an important part of computer programming. }+When a new product is released for testing to a company's own employees before exposing it outside the company, the product is said to be under alpha testing. Beta testing then is the pre-testing of hardware or software products with selected typical customers to discover inadequate features or possible product enhancements before it is released to the general public. ÓThe term alphanumeric refers to data or terms that consists of both numbers and alphabetic characters. Examples of alphanumeric terms: WD40, 5IVE, 2x4, R2D2, RU469, ICU812, OCT90, 1040EZ ˆThe ALU is the heart of the microprocessor, and one of the essential components. It is the operative base between the registers and the control block. It performs various forms of addition, subtraction, and the extension of these to multiplication, division, exponentiation. The logic mode relates to the operations of gating, masking, and other manipulations of the contents of the registers. Generally, ALU architecture handles 8-bit quantities through the accumulator while the register file is composed of three 16-bit registers. Because the accumulator and the ALU are often only 8 bits wide, these three general registers can be accessed by instructions that treat them as six 8-bit registers. The choice of concept is often up to the programmer. From a hardware standpoint, the processor on many systems operates on 8-bit bytes and all I/O operations use an 8-bit data path. Í]There are two main ways of doing things electronically, analog or digital. In the analog method, signals are continuously variable and the slightest change may be significant. Analog circuits are subject to drift, distortion, and noise, but they are capable of handling complex signals with relatively simple circuitry. Analog data transmissions require amplifiers, due to attenuation of the signal with distance, to boost or magnify the signal. pANSI is an abbreviation for American National Standards Institute. It is a non-governmental organization founded in 1918 that proposes, modifies, approves, and publishes data processing standards for voluntary use in the United States. ANSI is also the U.S. representative to the International Standards Organization (ISO) in Paris, and the International Electrotechnical commission (IEC). Any programming language that claims to conform to ANSI standards must pass all the tests for the standard syntax rules as set forth by ANSI. For more information contact ANSI, 1430 Broadway, New York, NY 10018 œDStatic electricity that builds-up on your body can be harmful to electronic components. If you plan to work inside the case of your computer, or with printed circuit boards, always insure that you are properly grounded. Anti-static products work in one of two ways: by helping prevent static buildup or by providing a convenient and safe means of draining the charge. In general, static drainage products are much more effective than static control products. Static control products include ungrounded floor mats, CRT screens, spray cleaners and wipes, and equipment dust covers. Static drainage products, which have a ground that ultimately ends in the earth, include grounded floor mats, dust covers, anti-glare screens, touch pads, desk pads, and some surge protectors. Note: Proper room humidification may provide enough of a discharge path to ground, making anti-static touch-pads unnecessary. kfIn computer graphics, when lines are drawn at an angle their appearance often takes on a jagged or stair-step effect. This is especially true on monitors with a poor resolution and is referred to as aliasing. Antialiasing is a desirable feature in a computer graphics system whereby the jagged or stair-step effect is automatically removed or reduced. J1America Online is an on-line service with a graphical interface started in 1988 for Apple and MacIntosh computers. In February of 1991, the PC version became available with EGA resolution. Services include: electronic mail, headline news, weather, stock market quotes, downloadable games, special interest groups, bulletin boards, on-line shopping, and limited research capabilities. For current fees and more information: America Online Quantum Computer Services 703-448-8700 8619 Westwood Center Drive, #200 800-827-6364 Vienna, VA 22182-9806 ÒhAPI is an abbreviation for Application Program Interface. APIs are the tools that program developers use to access the functionality of a computer's operating system and the services of its peripheral devices. Generally, APIs are system calls, routines, that allow programmers access to the services provided by the operating system. APIs can be used to manipulate files and directories, provide record locking and transaction tracking, semaphore control, interface to graphics adapters, and a wide variety of other services. On a Local Area Network, an API such as IBM's NetBIOS, provides applications with a uniform means of requesting services from the lower levels of the network operating system. c9APL stands for "A Programming Language", which was the title of a book written in 1962 by the creator of the language, Kenneth E. Iverson. Based on what was originally referred to as Iverson Notation, APL is an extremely concise programming language, designed for the manipulation of arrays. The arrays may be scalars, vectors, tables, or matrices of two or more dimensions, and may be composed of either numeric or alphanumeric information. Under Iverson's leadership, IBM introduced APL\360 in 1966. Since APL predates the introduction of personal computers, it was originally used only on mainframe computers. Since 1983, versions of APL have been available for the PC. Because of its expanded special character set, APL requires a special keyboard or macros for data entry. IBM's current mainframe and PC versions of APL are called APL2. Î,In the DOS environment, every disk file can have four attributes or characteristics associated with it. The one called the archive attribute is actually a bit which is set to one or zero depending on the status of the file. When the file is backed-up or archived the archive bit is set to one and when the file is changed the archive bit is reset to zero. The DOS ATTRIB command can be used to view and/or change the status of a file's archive bit. Ñ To the true definition, an archive file is one that has been copied onto an auxiliary storage medium such as disk or magnetic tape for the purpose of long-term retention. In the microcomputer world, an archive file is one that has been compressed, squashed, squeezed, crunched, and/or packed with a file archiving program in order to use less disk space and to reduce the transfer time when sending files between computers. Data Libraries store program and data files in compressed format and rename the files using the ".ARC" or ".ZIP" filename extension. For further information on the .ARC file compression and archiving programs, write to: System Enhancement Associates, Seattle, Washington x-ARCnet is a baseband, token-passing Local Area Network technology offering a flexible topology for connecting personal computers. The term ARCnet is an acronym for Attached Resource Computer network. It is one of the oldest LAN technologies and was originally developed by John Murphy of Datapoint Corp. ARCnet interface cards (or network controller boards) are manufactured by various vendors each having the capability of functioning with other ARCnet cards. That is, each PC workstation on a network could have an ARCnet card from a different manufacturer (in a star topology). LANs utilizing network interface cards are often referred to as media-sharing and are more flexible and provide faster performance than the RS-232 LANs. ARCnet LANs are capable of operating at speeds up to 2.5 megabits/second. IEEE 802.4 addresses the specifications for ARCnet cabling. íThe American Standard Code for Information Interchange is a standard seven-bit code that was created in 1965 by Robert W. Bemer and established to achieve compatibility between various types of data processing equipment. ASCII, pronounced "ask-key", is the common code for microcomputer equipment. The Standard ASCII Character Set consists of 128 decimal numbers ranging from zero through 127 assigned to letters, numbers, punctuation marks, and the most common special characters. The Extended ASCII Character Set also consists of 128 decimal numbers and ranges from 128 through 255 representing additional special, mathematical, graphic, and foreign characters. See the Reference Tables for the complete ASCII Character Sets. rxAn ASCII text file is a data file containing only alphanumeric and special characters that belong to the ASCII character sets. ASCII text files can be read by most modern word processing programs and then internally converted to another format so that special word processing features can be utilized. For example, there is no standard ASCII character that can be added to the beginning of a line of text that causes that line to be centered when output to the screen or to a printer. Each different word processing program may have a special control character for centering text. There are many different control characters utilized by different application programs for enabling or identifying special features. Files that contain these special control characters are not ASCII text files, and can only be properly utilized by the program that created them. DThe Association of Shareware Professionals is an organization of programmers founded in 1987. The primary goal of the association is to strengthen the future of shareware marketing as an alternative to traditional marketing. The ASP is also striving to help diskette vendors, the news media, and the general public to understand the nature and benefits of shareware. The major theme behind shareware programs is "Try before you buy". Users can evaluate the program on their own systems before making an investment. If the program proves to be useful, the user has a moral and legal obligation to register with the author. Address your written correspondence to: ASP, 545 Grover Road Muskegon, MI 49442 On CompuServe, GO SHARE, for public and private ASP forums. 'eGenerally speaking, each design of computer whether it be an IBM, Honeywell, Digital, or any other, has its own assembly language. Assembly language is a low-level programming language that uses mnemonic instructions, such as STO for store and SUB for subtract, instead of binary numbers to represent the corresponding machine language instruction. It is written to correspond to a specific computer's machine language. An assembler is a program that translates the assembly language symbolic code into its equivalent machine code. 5The asterisk is a character widely used in programming languages to indicate multiplication, such as 3 * 3. The asterisk is also used as an acceptable character in the syntax of a command line argument as a wildcard to represent one or more other characters. For example, consider the following DOS command line; DIR *.* The argument part, the *.* (star-dot-star) is used to indicate any combination of filename and file extension. The asterisk is known by other names such as star, splat, gear, mult, wildcard, and dingle. Å$When signals are sent to a computer at irregular intervals, they are described as asynchronous. When data is transmitted asynchronously, it is sent at irregular intervals by preceding each character with a start bit and following it with a stop bit. Asynchronous transmission allows a character to be sent at random after the preceding character has been sent, without regard to any timing device. Contrast with synchronous transmission. cThe set of commands that is used to control the operation of a modem is called the standard Hayes AT Command Set. Most of the commands are prefaced with an AT which stands for ATtention. For example, to dial the phone, the communications program would send the command "ATD" (ATtention, Dial) to the modem. In 1981, Hayes Microcomputer Products, Inc. produced the first modem to operate with a command set. It was called a smart modem because prior to that time modems only modulated and demodulated signals between the telephone line and the computer. They did not operate with a command set. OaATM is an abbreviation for Automatic Teller Machine. Modern banking facilities provide ATMs as a service to their customers so that deposits and withdrawals can be made at all hours often from terminals remotely located from the bank. An ATM can be a stand-alone unit or connected directly to the central computer system. The customer activates a transaction by inserting a plastic card into the terminal. The card contains a magnetic strip with the customer's account information. ATM is also an abbreviation for Asynchronous Transfer Mode, an emerging standard for cell-based data transport on high-speed LANs. The basic packet is a fixed-length cell of 53 octets (bytes), 5 of which are used for control functions and 48 for data. This permits digitized voice to be transmitted as packets beginning at speeds of 155 Mbps. úfAn attribute is a characteristic that describes data, or a data structure, or an element of a data model. An attribute is a word that describes the manner in which a variable is handled by the computer. For example, typical file attributes would be the file's size and the length of a record in a file. The DOS file attributes are stored in byte 11 of a directory entry and determine whether or not a file is declared read-only, hidden, a system file, or if the archive bit is on or off. •In computer-related operations, an audit trail is data in the form of a logical path linking a sequence of events. This data is used to trace or examine the transactions that have affected the contents of a database. In an accounting system, an audit trail may be automatically maintained by a special program feature. Pointers or records of transactions are stored so that the origin of specific figures can be easily identified. Network operating system software often includes a feature for maintaining an audit trail of events that take place throughout the network. It can be as simple as maintaining a log of who, when, where, and how long an individual was connected to the network. Or an elaborate audit trail can be activated which will keep records of almost every imaginable event. The level of sophistication depends on the network operating system and the needs of the organization. The AUI is an IEEE 802.3 standard designation for the cable that connects workstations on a local area network often using thick Ethernet cable. It is the interface between the medium attachment unit (MAU) and the data terminal equipment (DTE). The IEEE specification 10Base-5 is shorthand for a 10 megabits per second baseband medium with a maximum segment or trunk length of 500 meters. ziThe AUTOEXEC.BAT file is an operating system file that DOS searches for each time the microcomputer is booted. It is not required but provides many advantages. DOS only looks for it in the root directory of the boot device (either the A: floppy drive or the C: hard drive). The AUTOEXEC.BAT file is an ASCII text file and can be changed with any text editor program such as EDLIN. Since the DOS commands in the AUTOEXEC.BAT are executed each time the system is booted, the operating environment for each particular system can be optimized to take advantage of the attached hardware. Software applications that reside on the hard disk often require that certain parameters be defined in the DOS environment space. These SET commands can be placed in the AUTOEXEC.BAT file. If you have never seen one, at the C:\ prompt, enter the following command, TYPE AUTOEXEC.BAT uIWhen the hard disk drive is not in use the read/write heads are locked in their current position as a safety measure, but not necessarily away from critical areas of the disk platter(s). A hard disk drive feature that does ensure the read/write heads to be securely parked away from all critical areas of the platter is called automatic park. This feature is implemented whenever power is turned off or lost. Most hard drives that offer the automatic park feature use voice- coil technology. The mechanism that lifts the heads away from the platter when power is removed is called the automatic head lifter. #4AWG is an abbreviation for American Wire Gauge. It is a system for the measurement of the thickness of metal wire. The gauge number increases as the wire diameter decreases. For example, AWG number 10 has a diameter of 0.102 inches and AWG number 29 has a diameter of 0.011 inches. D A popular European typewriter or computer keyboard, with the characters "A, Z, E, R, T, and Y" as shown below. There are many other different keyboard styles in use throughout Europe. ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄ¿ ³ ³³ A ³³ Z ³³ E ³³ R ³³ T ³³ Y ³³ U ³³ I ³³ O ³³ P ³³ ³³ ³³ ³ ÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙ³ ³ ÚÄÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄÙ ³ ³ ³³ Q ³³ S ³³ D ³³ F ³³ G ³³ H ³³ J ³³ K ³³ L ³³ M ³³ ³³ ³ ÀÄÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÄÄÄÙ ÚÄÄÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄÄÄÄÄÄÄÄ¿ ³ ³³ W ³³ X ³³ C ³³ V ³³ B ³³ N ³³ ³³ ³³ ³³ ³³ ³ ÀÄÄÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÄÄÄÄÄÄÄÙ ÚÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄ¿ ³ ³³ SPACE BAR ³³ ³ ÀÄÄÄÄÄÄÙÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙÀÄÄÄÄÄÄÙ ^pA backbone network is a communication facility that is used to connect two or more networks. It normally operates at a significantly higher speed than the networks or file servers that it connects and may be of a different topolgy and use different protocols. Typically, user workstations are not connected directly to the network backbone. Õ(The background mode is the teleprocessing or multi-programming environment in which lower priority tasks are processed during a time when higher priority tasks are inactive. In a multitasking environment, to control a program operating in the background, it must be brought to the foreground with operating system commands. A background program, such as a printing task, is executed when a higher priority task is inactive. The foreground mode is the teleprocessing or multiprogramming environment in which high priority tasks are performed before those of a lower priority. Generally, there may be several background operations running, but only one foreground operation running, at any given instant. Ÿ_Copies of data and program files are called backups. It is always advisable to make backups of your data and programs. Microcomputers, like all things manufactured, are prey to human error and mechanical failure. No matter what type of backup hardware you choose, you still need a backup system, a strict routine for making backups. Most backup systems fit into one of two categories; tape or disk. íJA balun transformer is a connector that allows balanced cables to to be joined together with unbalanced cables. The electrical characteristics of each are matched so that data can be transmitted. For example, twisted pair (balanced) cables can be joined with unbalanced coaxial cable if the proper balun transformer is used. In an ARCnet local area network, in-line baluns can be used to convert the impedance of coaxial cable so that its signal can run on twisted-pair wiring. ;eGenerally, bandwidth is a measure of the range of frequencies within a radiation band required to transmit a particular signal. It measures, in millions of cycles per second, the difference between the lowest and highest signal frequencies. The bandwidth of a computer monitor is a measure of the rate that a monitor can handle information from the display adapter. The wider the bandwidth, the more information the monitor can carry, and the greater the resolution. For example, the CGA monitor which has a poor resolution, has a bandwidth of 30 MHz. 8XAs the name implies, Bar code is the code used on consumer products and inventory parts for identification purposes. The code is read with an optical wand or a stationary in-counter bar-code reader. The code consists of bars of varying thicknesses to represent characters and numerals. There are several product-marking codes, such as Universal Product Code (UPC), CODABAR, and MSI. º³Ûººº³Û³Ûºº³Û³º³ºº³Û³ A sample of a Bar code: º³Ûººº³Û³Ûºº³Û³º³ºº³Û³ º³Ûººº³Û³Ûºº³Û³º³ºº³Û³ º³Ûººº³Û³Ûºº³Û³º³ºº³Û³ º³Ûººº³Û³Ûºº³Û³º³ºº³Û³ As a point of interest, the city of Treasure Island, Florida sells bar code decals at the toll bridge for car windows so that residents can pass through toll free. "Baseband signaling is a method or technique for transmitting digital data at speeds of up to 10 million bits per second. Baseband transmission uses low-frequency signals over coaxial cable or twisted pair, limited in distance to less than 2000 feet. ARCnet and Ethernet local area networks utilize baseband signaling. Baseband handles digital data only, is relatively easy to install and modify, and is less expensive than broadband signaling which handles voice, data, video, and image transmissions over a greater distance. Ó]BASIC is a computer programming language, an acronym for Beginner's All-purpose Symbolic Instruction Code. Although it is a simple language to learn and use, it contains many advanced features for handling mathematical formulas and character strings. It is an interpretive language which means that each statement is translated and executed as it is encountered rather than having all the program statements compiled before execution. There are compilers for BASIC so that final versions of programs can be translated to executable code for faster run-time performance. BASIC was originally developed by John Kemeny and Thomas Kurtz in the mid-1960's at Dartmouth College in Hanover, New Hampshire. ³.A batch file is a set of commands which are stored in a disk file for execution by the operating system. Typically, a batch file is created to save time and reduce the possibility of error for tasks that are executed frequently. Personal computer users create a batch file called AUTOEXEC.BAT which is automatically executed by DOS each time the system is started. DOS batch files utilize the .BAT filename extension. É/There are electronic components on printed circuit boards of most microcomputers that need a constant supply of electrical energy in order to retain their stored information. One such component is the clock/calendar. It is kept active with dry cell batteries or with coin-shaped lithium batteries. When these batteries deteriorate and lose their power, the system clock fails to keep the correct time and date. Rather than input the correct time and date when the system is booted, it would be easier to simply replace the batteries. When this system set-up and timing information is retained by the use of a small battery inside the computer, the computer is said to have 'battery backup'. …tThe word baud is derived from the surname of J.M.E. Baudot (1845-1903), a French pioneer in the field of printing telegraphy and the inventor of the Baudot code. Baud is a unit of measurement that denotes the number of discrete signal elements, such as bits, that can be transmitted per second. Bits per second (bps) means the number of binary digits transmitted in one second. There is a difference between bps and baud rate, and the two are often confused. For example, a device such as a modem said to transmit at 2400 baud is not correct, it actually transmits 2400 bits per second. It is important to note that both baud rate and bps refer to the rate at which the bits within a single frame are transmitted. The gaps between the frames can be of variable length. Accordingly, neither baud rate nor bps refers to the rate at which information is actually being transferred. ÒA bulletin board system is a computer that operates with a program and a modem to allow other computers with modems to communicate with it, often on a round the clock basis. There are thousands of MS-DOS and PC-related bulletin board systems in the United States offering a wealth of information including libraries of shareware programs that can be downloaded. Most BBSs fall into one of five distinct categories. The general interest BBS caters to a large audience, with message bases devoted to several topics, a generous supply of shareware software, news, and entertainment. The technical BBS deals with questions about DOS, hardware and programming. System specific boards focus on some particular brand of computer system and contain compatibility tips and information on related issues. Special interest BBSs offer info on non-computer subjects. Other boards exist primarily as sources for the many shareware programs in their libraries of files. è>BCD, an acronym for Binary Coded Decimal, is a type of positional value code in which each decimal digit is binary coded into 4-bit "words". BCD is based on, and sometimes called, the 8421 code. It derives its name from the value assigned to each of four bit positions, with each set of four bits equal to one decimal. The decimal number 12, for example, would become 0001 0010 in BCD. ÚÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ Decimal ³ 8421 Binary ³ ³ Decimal ³ 8421 Binary ³ ÃÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ ÃÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ ³ 0 ³ 0000 ³ ³ 5 ³ 0101 ³ ³ 1 ³ 0001 ³ ³ 6 ³ 0110 ³ ³ 2 ³ 0010 ³ ³ 7 ³ 0111 ³ ³ 3 ³ 0011 ³ ³ 8 ³ 1000 ³ ³ 4 ³ 0100 ³ ³ 9 ³ 1001 ³ ÀÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ û+In a token-ring network, when an adapter detects a hardware failure on the ring, it broadcasts a frame with a message informing other stations that the token passing has been suspended. The message or frame is called a beacon. The term broadcast storm is often used to describe a situation on a token-ring network when a device is not communicating properly and causes an excessive amount of traffic to be generated. This in turn causes the network response time at the workstation to increase. ¤'This list of standard AT&T Bell modems are the most popular models. Corresponding CCITT Recommendations are listed in parenthesis. Bell 103 - Asynchronous at 300 bps, full duplex, FDX. (V.21) Bell 212A - Asynchronous at 300 bps, synchronous at 1200 bps, FDX. (V.22) Bell 201 - Synchronous at 2400 bps, half duplex on 2-wire dial-up, (V.26) full duplex on 4-wire leased line. Bell 208 - Synchronous at 4800 bps, half duplex on 2-wire dial-up. (V.27) FDX on 4-wire leased line. Fall-back rate is 2400 bps. Bell 209 - Synchronous at 9600 bps, full duplex requires 4-wire (V.29) leased line. Fall-back rates are 7200 and 4800 bps. wGA benchmark is a process or program that can be executed to measure and compare the performance of one system against another. Testing the relative performance of microcomputer systems must deal with the problem of different CPUs, different FPUs, and different operating systems. Benchmark tests should be designed on some sort of common ground so that the results present a true measure of system performance even across brandnames and architectures. There should be low-level tests to measure floating point operations and application-level tests to measure things like the speed of spreadsheet re-calculations. ºPA flexible disk storage system that rivals hard disks for data capacity and access speed. The technology is based on the principles of aerodynamics that Daniel Bernoulli discovered in the 18th century. In the early 1980's, Iomega Corp. introduced the Bernoulli Box, which uses replaceable 8-inch or 5.25" disk cartridges. The removable Bernoulli drive cartridges can be used to backup a hard drive or in place of a hard drive. -The base-2 number system in which only the digits 1 and 0 are used is referred to as the binary system. The base-2 or binary system lets us express any number, if we have enough bits, as a combination of 1's and 0's. Because these digits can be used to represent two states, on and off or true and false, which in turn can be represented by two voltage levels in an electronic device, the binary system is at the heart of digital computing. Binary numbers are typically written as four-digit combinations. ádThe Basic Input/Output System, resident on a chip which plugs into the motherboard of a microcomputer, is a system program. The BIOS is responsible for handling the details of the input and output operations, including the task of relating a program's logical records to a peripheral device's physical records. The BIOS contains routines tailored to the specific requirements of each peripheral device. These routines are called drivers, or device handlers. As an example, a video BIOS consists of instructions on ROM that interpret and execute video requests from applications software. The BIOS executes these software requests by interacting with the video memory registers, the CPU, and the monitor or printer. IFBit is an abbreviation for Binary digit Computer words and data are made-up of bits, the smallest unit of information. Most personal computers operate with 16-bit words. A bit can be either zero or one, represented in a circuit by an off or on state, respectively. The bits are set on or off to store data or to form a code which in turn sends instructions to the central processing unit. The term 'bit' was reportedly first used in 1946 by American John Tukey, a leading statistician and presidential advisor. Two bits is still a quarter, a quarter of a byte. :A method of storing graphics information in memory. A bit devoted to each pixel (picture element) on the screen indicates whether that pixel is on or off. A bit-map contains a bit for each point or dot on a video display screen and allows for very fine resolution since any point or pixel on the screen can be addressed. A byte of information, for example, could describe the appearance of eight pixels. A greater number of bits could be used to describe each pixel's color, intensity, and other display characteristics. áWBIX is an on-line service provided by BYTE magazine, published by McGraw-Hill, Inc. Services include: Industry news, downloadable software, powerful electronic mail, previews of upcoming BYTE articles, the full text of published issues of BYTE magazine, conferences on computer-related topics, and source code for BYTE benchmarks and non-commercial software mentioned in featured articles. For current fees and more information, call 800-227-2983 or 603-924-7681 (XBritish National Connector is a nickname for the BNC connector. BNC actually is an abbreviation for Bayonet Neill-Concelman. The term bayonet describes the push and turn action necessary to lock the male and female parts together. Mr. Neill-Concelman invented it. Originally designed in England for television set antennas, the BNC is a type of connector designed for use with coaxial cabling. They lock together when the male part is inserted into the female part and rotated 90 degrees to lock it in place. In the mid-1950's, the BNC became popular with military avionics equipment, especially common in VHF and UHF radio communications. Today, BNC connectors are very popular in Local Area Networks for connecting microcomputers together and are used in both Ethernet and ARCnet LANs. `BoCoEx - Boston Computer Exchange, 1-617-542-4414, Boston, MA NACOMEX - National Computer Exchange, 1-212-614-0700, New York, NY Both of these organizations are computerized brokerage firms publishing daily lists of used computer prices. beBOF and TOF are abbreviations for the Beginning or Top of File. They are codes placed by a program before the first byte in a file and are used by the computer's operating system to keep track of locations within a file with respect to the first byte or character in the file. On disk, a data directory or catalog usually contains the location of a file based on the file's BOF or TOF relative to the first storage location on the disk. In an indexed database, the BOF or TOF marks the first indexed record. An EOF, End of File, is a code that marks the true end of a file. Since disk space is allocated in blocks of bytes, the EOF code is used to identify the actual point at which a file ends rather than the end of the data in the file. The EOF mark is represented by the ASCII code decimal value 26 or hexadecimal 1A, or Control-Z character. 5Boolean algebra is a deductive system or process of reasoning named after George Boole, an English mathematician (1815-1864). It is a system of theorems which uses symbolic logic to denote classes of elements, true or false propositions, and on-off logic circuit elements. It is fundamental to computers; all digital computers use the two-state or two variable Boolean algebra in construction and operation. The Boolean operators, which are also called logical operators, are AND (conjunction) accepts two inputs, both must be one (or true) to produce an output of one (or true). OR (inclusion) accepts two inputs, either one or both inputs must be one (or true) to produce an output of one (or true). NOT (negation) reverses the input, one's become zero's. »|A computer's operating system is initiated with a boot procedure, a start-up from scratch. For personal computers using DOS, when power is applied the CPU initializes itself and reads the code stored in a read-only memory chip, called the ROM BIOS. After some hardware initialization, the boot-loader program loads one program from disk which occupies the first file position and must be the first entry in the boot disk's root directory. That program is usually called IO.SYS. IO.SYS (or IBMBIO.COM) finishes initializing the hardware and loads the Disk Operating System. DOS reads a file called CONFIG.SYS, if it exists, and carries out the commands it contains, such as modifying internal DOS tables and/or loading and initializing device drivers. COMMAND.COM is loaded next which executes each line of the AUTOEXEC.BAT file, if it exists, and finally displays a prompt string on the screen waiting for the user to enter a command. tGIn local area networks, a bridge is an interconnection device between two networks of the same type using similar or dissimilar data links such as Ethernet, token-ring, and X.25. Bridges function at the data link layer of the OSI model. Specifically, bridges operate at the media access control or MAC sublayer of the data link layer. For this reason they are often called MAC-layer bridges. A bridge monitors all traffic on the two subnets that it links. If a bridge links LANs that have dissimilar MAC layers, it does the processing necessary to change, for example, an Ethernet packet to a token-ring packet. An internal bridge resides within the file server. An external bridge is located in a workstation apart from the host or server. External bridges may be dedicated or non-dedicated. When a computer is used only as a bridge, it is a dedicated bridge. ÛcGenerally, in data communications, both terms broadband and wideband are used to describe transmission facilities capable of handling frequencies greater than those required for voice grade communications, ie. baseband. Broadband communication channels can transmit data, voice, and video signals at rates up to five million bits per second over long distances using high frequencies. Broadband transmissions require modems for connecting terminals and computers to the network. Using frequency division multiplexing, just like cable TV, many different signals or sets of data can be transmitted simultaneously. Compare broadband to baseband signaling which transmits at lower speeds over shorter distances. :Memory in which magnetic regions are suspended in crystal film is called bubble memory. It maintains its data when the power is off, and is therefore referred to as non-volatile read/write memory. A typical bubble memory device may contain up to 4 million bits or bubbles, that's 500,000 bytes. One or more such devices may be combined with special interface logic to form a bubble memory system with an information access time of several milliseconds. Because bubble memory systems require relatively little power and retain information even when power is removed, they are sometimes used as disk drive replacements in portable computers. Bubble memory is also commonly used as solid-state "disk" drives in environments where conventional, electromechanical drives are unacceptable, such as factories. ñ{A buffer is often a block of memory that the operating system uses to temporarily store data. Several buffers can be defined at system configuration time based on your applications. The DOS configuration file called CONFIG.SYS, which is read when the system is booted, can include a BUFFERS command line to set aside a number of memory blocks for temporary data storage. If the directory structure is large, the number of buffers should be set to about 30. A buffer can also be part of a peripheral device containing its own memory to receive the output of a task quicker than the device can perform the task's instructions, thus freeing the processor for other operations. Modern printers are designed and built with print buffers. ÎrAn error or mistake in a program, or a hardware malfunction in a computer system is referred to as a bug. Debug refers to the act of tracing and correcting errors in programming code or resolving hardware malfunctions in a computer system. The first real computer bug was found trapped in one of the thousands of electromechanical relays inside the Mark I computer at Harvard University in the 1940's. U.S. Navy officer Grace Murray Hopper found the remains of a moth blocking an electrical switch. The incident was documented with an entry in the logbook along with the moth. From then on, the term "debugging" was used to describe the process of finding the cause of errors in computer programs. ê%In the world of computers, a bus is a set of wires or lines used for data transfer among the various components of a computer system. Actually, the bus is made up of traces on the printed circuit boards. All the major components such as the microprocessor, the disk drive controller, random access memory, and the input/output ports are electrically connected by the bus so that information can be passed. The first IBM microcomputers and compatibles such as the PC and the PC-XT (8086 and the 8088) utilize an 8-bit data bus. The IBM-AT (80286) systems provide both the 8-bit and the 16-bit bus. Systems with the 80386 and 80486 microprocessors can transfer data along a 32-bit bus, 32 bits if data are sent at the same time. ðcA byte is most often defined as 8 bits of data. The largest decimal number that can be stored in one byte is 255, that would be with all eight bits set to 1. Even with computers that operate with 32 or 36 bit words, the term byte still refers to 8 bits of data. In 1964, the 8-bit byte became a standard with the IBM 360 computer. Half a byte is a nibble or nybble, 4 bits. Two bits is a still a quarter, a quarter of a byte. See the Conversion Table "Bytes to Terabytes" ú6The C-Language is the structured, modular, compiled, general- purpose programming language traditionally used for systems programming. It is referred to both as a low-level language and as a middle-level language. It is portable or generally machine independent which means that programs written in 'C' can be easily transferred between different computers. The C-Language has been closely associated with the UNIX operating system, since it was developed on that system, and since UNIX and its application software are written in 'C'. 'C' was originally designed and written by Dennis M. Ritchie. The most widely known description of 'C' is found in The C Programming Language, by Brian W. Kernighan and Dennis M. Ritchie (Prentice-Hall) ":A cache is a memory medium that provides faster access than the medium where the data is customarily stored. A cache memory architecture combines SRAM's speed with DRAM's cost effectiveness. It provides a small amount (usually 64KB or less) of fast SRAM (the cache) that is logically located between the processor and main memory (which is usually simple DRAM.) A cache memory system is relatively expensive because it requires SRAM chips for the cache and complex cache control circuitry to regulate the operation of the cache. 3YA computer program that aids in the design and drawing of a project is referred to as CAD software. Vast libraries of images are available at reasonable prices and CAD software makes it easy to modify them for a specific purpose. Because CAD drawings are recorded as lines and arcs, with mathematical coordinates for the start and stop points, they are accurate and can be reproduced at any size or scale without losing quality. When a change is made, the relationship to all other elements in the drawing remains constant. CAD files are easily transferred between different software packages and computer systems. Most publishers have adopted AutoCAD's .DXF file transfer format. Examples of Computer-Aided Design packages: AutoCAD, Drafix 1 Plus, FastCAD, VersaCAD, In*A*Vision ˜FThe National Institute for Occupational Safety and Health reports that thousands of Americans, most of them heavy keyboard users, suffer from a painful hand injury called Carpal Tunnel Syndrome. CTS gets its name from the narrow tunnel in the wrist connecting ligament and bone. The median nerve, which carries impulses from the brain to the hand, and the tendons that open and close the hand are found in the carpal tunnel. When undue pressure is put on the tendons, they can swell and compress the median nerve, causing numbness, weakness, tingling, and burning in the fingers and hands. A principal cause of CTS is stiff, static wrist position. You can prevent CTS by placing your keyboard so that 90-degree angles are formed at the elbows with your arms held loosely at your sides. Take time to shake out your hands and arms when they feel tired, and try not to punch the keys too forcefully. pWhen modems are used to send data between computers, the sending modem transmits a high pitched tone (the carrier) to the receiving modem. When the receiving modem detects this tone, a carrier detect signal is returned to the sending modem. The carrier detect signal is defined in the RS-232 specification and is the same as the Received Line Signal Detector. It is a modem interface signal that indicates to the attached data terminal equipment (DTE) that it is receiving a signal from the distant modem. =CASE, or Computer-Aided Software Engineering, can be defined as software automation. It is a tool for programmers, analysts, and systems engineers. CASE provides software tools and utilities to help corporate planners plan, and to document their work; to support systems analysts in analyzing and designing systems, and to document those tasks. Prior to the late 1980's, CASE software packages were mostly available only on mainframe computers, and their cost were in the five- and six-figure price range. Now the majority of them run on microcomputers. ÍXComit‚ Consultatif International T‚l‚graphique et T‚l‚phonique The CCITT is an international consultative committee, organized by the United Nations. It makes recommendations for international communications, which are frequently adopted as standards. It also develops interface, modem, and data network recommendations. Membership includes governmental Post, Telephone, and Telegraph Authorities, scientific and trade associations, and private companies. CCITT is part of the International Telecommunications Union, a United Nations treaty organization in Geneva, Switzerland. The popular standard X.25 protocol for access to packet-switched networks was originally a recommendation of CCITT. y'CD-I is a specification for a complete hardware/software product that includes a CD-ROM player, a Motorola 68000-family CPU, and special audio and video processing hardware. CD-I is an extension of CD-ROM that allows sound and video images to be stored as standard analog signals alongside other digital information. Although CD-I has a wide range of capabilities, including audio with compact disk quality, it cannot display continuous full-screen, full-motion video, and it cannot run on hardware that doesn't precisely conform to the specification. The CD-I concept was introduced in 1986 by Philips and Sony. ÂA CD-ROM is a computer peripheral device that employs compact disc (CD) technology to store large amounts of data for later retrieval. Philips and Sony developed CD-ROM in 1983. As a read-only data storage medium, CD-ROM disks can store digitized text, data, images, and sound. They are stamped, like record albums, from a metal master. CD-ROM disks are by definition unerasable and incapable of being written to by the user. Current CD-ROM discs can hold 680 megabytes of information. That's the equivalent of more than 275,000 printed pages of text, or 74 minutes of audio, or more than 1800 double-density 360K diskettes. Although CD-ROM drives access data randomly, their typical data transfer rate is an unimpressive 1.2 Mbits per second, substantially less than the 5 Mbits per second data transfer rate of most common hard disks. The physical controller interface for CD-ROM drives varies, but the popular SCSI is clearly dominant. With respect to spreadsheet operations, a cell is one individual element of the matrix that makes up the spreadsheet. Each cell of a spreadsheet has an address consisting of its row and column. For example, cell "B9" is the rectangular area formed at the intersection of row "B" and column "9". Cells can contain a numerical constant, a formula, or a label. If a formula is placed in a cell, the spreadsheet program will display the results of the formula rather than the formula itself. The cell format determines how values and labels are displayed. For example, a worksheet dealing with financial figures may take advantage of a global currency format. Each cell value would be displayed with the dollar sign ($) and 2 places to the right of the decimal point. sBAs a type of data transfer, the Centronics parallel format is an unofficial standard. Almost without exception, a parallel interface in a microcomputer printer will be a Centronics interface. It was developed by the Centronics Data Computer Corporation in the early days of microcomputing, and because of its usefulness, became a de facto standard. Data is transferred 8 bits at a time. The printer and the CPU communicate using three handshaking lines: Data Strobe, Acknowledge, and Busy. A block of RAM in the printer acts as a buffer or temporary storage for the data. The larger the buffer, the more data the printer can accept before sending the Busy signal to the CPU. The disadvantage to the parallel Centronics system of data transfer is the fact that parallel cables longer than about ten feet tend to be sensitive to electrical noise or interference. XThe Color Graphics Adapter was IBM's first color adapter for the personal computer. It is compatible with red-green-blue (RGB) monitors, color composite and monochrome composite monitors as well as with standard television sets that have RF modulators. CGA produces characters with an 8 by 8 pixel dot box and graphics in two modes: medium and high resolution. The CGA operates at a horizontal scanning frequency of 15.75 KHz. A monitor must have a bandwidth of at least 14 MHz to be compatible with the CGA. Compared to today's EGA and VGA monitors, the CGA is poor quality. óA chip is an integrated circuit created on a tiny silicon flake upon which a large number of gates and the paths connecting them are formed by very thin films of metal acting as wires. The chip can be used as main memory or as the CPU. When both memory and logic capabilities are contained on the same chip, it is called a microprocessor or a computer on a chip. The chip consumes very little power, is compact, inexpensive, and can process a million or more instructions per second. v9CompuServe Information Service is the name of the company that provides an on-line service called CompuServe. It is one of the largest in the world and is a text-based system operated on a mainframe computer. Services include: libraries of downloadable programs and data, electronic mail with a gateway to other systems, hundreds of conferences called forums for special interest groups, electronic shopping mall, multi-player games, and research capabilities. For current fees and more information, CompuServe Information Service, 800-848-8199 P.O. Box 20212 5000 Arlington Centre Blvd. Columbus, OH 43220 4Pronounced "sisk", CISC refers to traditional computers that operate with large sets of instructions. Most modern computers fall into this category, including the IBM-compatible microcomputers. As computing technology evolved, instruction sets expanded to include newer instructions which are complex in nature and require several to many execution cycles and, therefore, more time to complete. Computers that operate with system software based on these instruction sets have been referred to as complex instruction set computers (CISC). Contrast with RISC (Reduced Instruction Set Computer) computers, which have far fewer instructions. †:The verb "to click" refers to the depressing of the button or buttons of a mouse. Computer programs that interface with the operator through the use of a handheld mouse device allow the user to make choices on the screen by moving the cursor into a defined area and clicking a mouse button. A double click refers to the pressing of a mouse button twice in rapid succession. ¥p"Client-server" is a term used in a broad sense to refer to the relationship between the receiver and the provider of a service. In today's world of microcomputers, the term client-server refers to a networked system where front-end applications, as the client, make service requests upon another networked system. Client-server relationships are primarily defined by software. In a local area network, the workstation is the client and the file server is the server. But client-server systems are inherently more complex than file server systems. Two disparate programs must work in tandem, and there are many more decisions to make about separating data and processing between the client workstations and the database server. The database server encapsulates database files and indexes, restricts access, enforces security, and provides applications with a consistent interface to data via a data dictionary. «Graphic images or files that can be imported to word processing and desktop publishing documents are called electronic clip art. Clip art for computers, just as in the printing and art industry, is available in various graphics file formats and is typically available as specialized libraries for different purposes such as medical, business, holiday seasons, sports, and so on. As an example, your company logo could be scanned with a graphics hand scanner, saved as a clip art file, and later imported with your desktop publishing program to a document. There are 2 types of clip art files, object oriented and bit-mapped. The object oriented uses draw-program-type line art format, and will always print a sharp image at any size, at the highest resolution. Bit-mapped or paint-type clip art can be manipulated by adding text, changing its size, rotating it, or stretching it, but it becomes jagged when enlarged. pA computer's clock is an internal timing device, often referred to as the system clock. The clock speed is determined by a quartz crystal. Every computer system utilizes a quartz crystal to regulate the system clock. When the machine is turned on, electric current causes the precisely cut sliver of quartz crystal to deform or vibrate, at a constant rate, millions of times per second. A voltage pulse is emitted with each vibration which, along with other signals, controls the pace of action and ensures that the circuits do not get out of phase. The system clock speed is measured in megahertz, MHz. ©ZA clone is a copy or a look-alike. Clones are not the result of an original idea or a new design; they are copies. In the world of microcomputers, the term clone most often refers to a computer system that resembles one of IBM's personal computers. Shortly after IBM introduced the PC, the XT, and the AT, clones appeared on the market claiming to be IBM-compatible. Some clones were more compatible than others. û~A cluster is a group of sectors on a hard disk or floppy disk that forms the fundamental unit of storage allocated by the operating system. The number of sectors in a cluster is determined by the computer's operating system, not its hardware. –ECoaxial cable is a data transmission medium noted for its wide bandwidth and for its low susceptibility to interference. Signals are transmitted inside a fully enclosed environment, an outer conductor or screen which surrounds an inner conductor. The conductors are commonly separated by a solid insulating material. Coaxial cable has a greater transmission capacity or bandwidth than standard twisted pair telephone wires. Coax cable is used in connecting workstations in a network of microcomputers. For example, local area networks using ARCnet technology are tied together with coaxial cable. See the Table "Local Area Network Cabling" ý<COBOL is a high-level computer programming language. The name is an acronym from COmmon Business Oriented Language. Since typical business-oriented applications require more data manipulation as input and output than extensive computation, COBOL is the preferred programming approach in the business world. COBOL was originally designed for mainframes but is now appearing on microcomputers to allow personal computer users to take advantage of the massive amount of COBOL software available. Õ6Code page switching is a DOS feature, versions 3.3 and later, that changes the characters displayed on the screen or printed on an output device. It requires an EGA monitor or better and a graphics printer compatible with the IBM models. For example, DOS 3.3 provides several pairs of code pages for displaying international characters. ÚÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ Code Page ³ Language ³ ÃÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ ³ 850 ³ Multilingual, for most European and North and South ³ ³ ³ American countries. ³ ³ 860 ³ Portuguese ³ ³ 863 ³ Canadian French ³ ³ 865 ³ Norwegian and Danish ³ ÀÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ NA computer's operating system is initiated with a boot procedure, a start-up from scratch. The IBM-compatible personal computers can be either cold booted or warm booted. A cold boot process begins with turning on the computer's power. Typically, the cold boot process consists of basic hardware checking followed by loading of the operating system from disk into memory. It is not always necessary to turn-off the power and then re-apply it to start the boot procedure. The system can be warm booted by depressing the following three keys at the same time: CTRL-ALT-DEL. Ö,A COM port is a communications channel or pathway over which data is transferred between remote computing devices. IBM-compatible microcomputers operating under DOS can have as many as four COM ports, COM1, COM2, COM3, and COM4. These COM ports are actually serial ports most often used with a modem to establish a communications channel over the telephone lines. The COM ports are also used to send data to a serial printer or to connect a serial mouse. æ-Comma-quote-delimited is an industry standard file format or record layout for transferring data between software applications. It is also called comma-delimited. The information in each record of the file is standard ASCII text. Each record contains a number of fields separated by commas and the data in each field begins and ends with a quote character. dBase, FoxBase, FoxPro, Clipper, and the other xBase products provide the capability of importing and exporting data in this format. The following sample records are comma-quote-delimited: "Sarah Peudic","14 Hospice Way","San Jose","CA","96370" "Zeek Branlon","4915 22nd Avenue North","St.Petersburg","FL","33710" "Sapnim Mann","P.O. Box 23","Chicago","IL","60602" øoA compiler is a program that translates a source program written in a high-level language into its equivalent machine language. The output from a compiler is called an object program. A compiler can also produce a program listing and diagnostics that may result from errors detected during the translation. Most programming languages have a compiler, for example, a FORTRAN compiler, or a COBOL compiler, TURBO-C compiler. The compiler also checks a computer program for syntax errors. û'A monitor that accepts a video signal similar to that received by a standard television set is called a composite monitor. That is, the signal provides luminance (brightness) data that monochrome and color monitors use, but the signal also has a sideband that carries the hue and saturation data that only a color monitor can use. A monochrome composite monitor uses the signal to display shades of grey as equivalents to the colors that would appear on a color composite monitor that received the same signal. Color Graphic Adapters (CGA) can provide output suitable for composite monitors; however the clarity of such monitors is inferior to that provided by TTL monitors. Composite monitors are rarely used with IBM PCs and compatibles. ¼6A computer is an electronic device for performing high-speed arithmetic and logical operations. There are five key parts to a computer: the central processor, the arithmetic logic unit, the memory, and the input and output devices. Most of our conventional computers adhere to the design concept referred to as the Von Neuman architecture. The three general classifications of computers are the microcomputer, the minicomputer, and the mainframe, whose differences depend on the type of processor, size of memory, and the input/output devices utilized. Because of the rapid advances in computer technology, the boundaries between these classifications are not clearly defined. G%There are many different computer languages for writing programs just as there are different spoken languages. The following examples of computer programming languages are defined further in this PC-GLOSSARY: Ada ALGOL BASIC C-Language COBOL FORTRAN PC Forth LISP Pascal PROLOG @JA computer program is a series of statements instructing the computer to perform a task or process data. The program may be in a high-level source code form, which requires intermediate processing before the computer can execute it, or it may be in an object form which can be directly executed by the computer. XWhen two or more items, such as character strings or files, are joined together end to end to form a larger unit, they are said to have been concatenated. Two data files can be concatenated by appending all the records in one file to the end of the records in another file. The larger file is then said to be a concatenated data set. †*Conditional branch A program instruction in which a condition is tested to determine whether a branch will occur is called a conditional branch. Unconditional branch A program instruction or statement that does not test a condition before a branch occurs is called an unconditional branch. Program execution then jumps to another location, no matter what condition exists. úLThe CONFIG.SYS file is an operating system file that DOS searches for each time the microcomputer is booted. It is not required but provides many advantages. DOS only looks for it in the root directory of the boot device (either the A: floppy drive or the C: hard drive). Since the DOS commands in the CONFIG.SYS are executed each time the system is booted, the operating environment for each particular system can be optimized to take advantage of the attached hardware. The CONFIG.SYS file is an ASCII text file and can be changed with any text editor program such as EDLIN. In order for the changes to take affect, the system must be re-booted. If you have never seen one, at the C:\ prompt, enter the following command, TYPE CONFIG.SYS nzThe term contiguous designates adjacent storage locations in main memory or non-fragmented file space on a disk. Oftentimes, as a result of extensive editing of a disk file, the file becomes fragmented on the disk, broken into parts which reside in different locations with pointers tying the file together. The file is then referred to as non-contiguous. ;}Special characters are sometimes embedded in a data item to specify an operation to be performed. For example, a line to be printed could contain a control character indicating that the printer should advance two lines before printing on the page. Throughout this glossary some of the words that appear on the screen are displayed in a highlighted fashion or in different colors. That feature is made possible by placing a control character before and after those words in the pre-compiled version of this glossary. See the Table "ASCII Control Codes" R[If your IBM-compatible computer hasn't locked-up, and the keyboard is active, the system can be warm booted by depressing the following three keys simultaneously: Ctrl-Alt-Del A computer's operating system is initiated with a boot procedure, a start-up from scratch. When your system is warm booted, the contents of memory are not actually erased. The operating system is simply reloaded, and the pointers to the beginning of available memory are reset. In fact, a DOS program called DEBUG can be used to read from the part of memory that was in use prior to the warm boot. ]1The Intel 8086 and 8088 microprocessor chips can address only up to 1024 kilobytes of Random Access Memory (RAM). The Intel 80286, 80386 and 80486 CPU chips can address more than 1024 kilobytes of memory. Conventional memory refers to the memory space between zero and 1024 KB that is directly addressable by the 8086 and 8088 CPUs or by the 80286, 80386 and 80486 CPUs operating in real mode. DOS and its applications are designed to use only the lower 640K of this conventional memory space. The remaining 384K is used for video RAM, the machine's BIOS, and/or RAM for hardware cards. G'Convergence is an attribute of a color monitor that describes its ability to focus the three colored electron beams on a single point. The three colors, red, green, and blue that make up each pixel are shot from electron guns. The sharpness of the image on the screen is determined by the dot pitch and the quality of the convergence. Poor convergence causes the characters on the screen to appear fuzzy and could cause headaches and eyestrain. Unfortunately, poor convergence quality cannot be corrected without opening the monitor and adjusting the electron guns. œ}Since it is illegal to make a copy of copyrighted software and pass it along to another person, many software developers devise methods to prevent or discourage this unauthorized duplication. Although copy protection has been implemented using various techniques, sometimes very sophisticated, there is often another program, called a copy buster, to unlock or override the copy protection scheme. Since the copy protection schemes can often be broken and because they cause the purchaser unnecessary inconveniences when moving the programs to a new hard disk, by the late 1980's most copy protection had been removed from personal computer software. EdA copyright is the legal, exclusive right to the publication, production, or sale of the rights to a literary, dramatic, musical, or artistic work, or to the use of a commercial print or label, granted by law for a specified period of time to an author, artist, composer, programmer, etc. If the product is a computer program such as this PC-GLOSSARY, it must include the statutory copyright notice like the one that appears on the opening screen, on all source code listings, on the diskette label, and on all documentation. Since the United States maintains a free-enterprise system, any work that is not properly protected by copyright, is considered to be in the public domain where anyone is free to use it. A copyright is registered by depositing a copy of the work with the Copyright Office in Washington D.C. b[The earliest type of memory used in computers, core memory was composed of storage units, called magnetic cores, made from a ferro-magnetic material and magnetized in either of two directions to store a bit. Core memory, now obsolete, was non-volatile and had a destructive read property requiring that data be restored after it had been read. úCP/M is an acronym for Control Program/Microcomputer. It is an operating system created by Gary Kildall, the founder of Digital Research. It was created for the old 8-bit microcomputers that used the 8080, 8085, and Z-80 microprocessors. It was the dominant operating system, before DOS, for personal computers of the non-Apple variety. CP/M included the Console Command Processor (CCP) and BDOS, the Basic Disk Operating System. It allowed users to install a variety of video displays and disk systems and actually made them work well together, a not-so-common situation in the 1970's. Actually, Microsoft Corp. bought the rights to a CP/M clone which had been developed by Seattle Computer Products and sold it to IBM as PC-DOS in 1981. vqEvery computer has a Central Processing Unit. The CPU is the portion of a computer where instructions are fetched, decoded, and executed. The overall activity of the computer is controlled by the CPU. It consists essentially of an arithmetic unit, a control unit, and an internal memory. A minimum requirement is three registers, a decode and control section, an adder, and two memory buffers. The control of other functions is exercised through the interpretation and execution of instructions. Today's CPUs for microcomputers are contained in chips small enough to easily fit in the palm of your hand. x*The term 'carriage return' originally defined the typewriter key that returns the carriage to the initial position on a line. The operator would then advance the paper one line to begin typing on the next line. On the keyboards used with today's computers, the carriage return is the character code that is often used as an end of line or end of command delimiter. 'Carriage return' is actually an improper term for the key labeled RETURN or ENTER on most modern keyboards. On many computer systems, the carriage return or a carriage return and linefeed pair (CR/LF) is used to end a line of text in a text file. ÇA computer system or program is said to crash when it has become inoperable because of a malfunction in the equipment or the software. One of the most common reasons for a system crash is a fluctuation or loss of power supply. It is wise to postpone important computer operations during a thunder storm. In most cases, when the system crashes due to a power fluctuation, rebooting the system will normally restore proper operations. However, one of the most dreaded types of crashes is the head crash. A head crash, usually caused by some sort of disk contamination, occurs when the read/write heads collide with the disk surface, resulting not only in lost data, but also damaged hardware. ^RCRC is an abbreviation for Cyclic Redundancy Check. To determine whether an error has occurred during the reading, writing, or transmission of data, a CRC is performed by calculating the CRC character, and comparing its value to the CRC character already present in that block of data. If they are equal, the data is assumed to be correct. ¸CRT is an abbreviation for Cathode Ray Tube. A cathode ray tube is a display screen like that of a television receiver used with computer systems for viewing data. A CRT or monitor for use with microcomputers typically displays 20 to 24 lines of data with 80 to 132 characters per line. Conventional CRT displays produce an image by directing an electron beam on a phosphorescent coating on the glass face of the tube. When struck by the electron beam, the phosphor glows, producing the light that reaches our eyes. When the beam stops, the light quickly fades. Different phosphor compositions control how long the glow lasts, and with color CRTs, what colors are produced. âVCarrier-Sense Multiple Access/Collision Detection (CSMA/CD) is a network access scheme. It is a method by which a network station obtains use of the physical network channel to send a message across the network. It allows all network users equal access to the one set of cables that interconnect the network. No central node controls access. CSMA/CD is used predominantly with bus topologies, like Ethernet. When it detects a clear channel (carrier sensing), a node transmits its message marked with the address of the receiver. All idle stations (those not transmitting) continuously monitor the channel for messages. The receiver of a message returns an acknowledgment of receipt. The sender, meanwhile, awaits the acknowledgment. If not received after a specified amount of time, the sender assumes that a collision has occurred and re-sends the message after a random amount of time. Collisions occur when two or more stations attempt to transmit simultaneously. ãCUA is an IBM standard user interface for displaying data on the screen. It is part of the SAA specifications which include OS/2 Presentaion Manager and the character-based formats of the 3270 terminals. The purpose of the CUA standard is to provide a consistent screen appearance across hardware platforms and between various software applications. CUA includes many of the graphical user interface (GUI) tools and techniques found in X-windows and the MAC interface. t*A cursor is the blinking or flashing indicator on a display screen which identifies a location. The cursor is often a short highlighted line that appears under the space where one character is to be entered or replaced. Modern keyboards are equipped with cursor control keys usually labeled with directional arrows, for left-or-right and up-or-down movement. LCybernetics is the field of science involved in the comparative study of organic and machine processes. It explores the similarities and differences between machines and human beings. Cybernetics often refers to robots which imitate human behavior. rWith magnetic disks, a cylinder consists of a vertical column of tracks on a disk platter or disk pack. With floppy disks that have only one disk platter, a cylinder consists of the top and bottom tracks with the same track number. On disk packs that have multiple platters, a cylinder consists of all the same numbered tracks on both sides of all platters. Õ=A daisy chain is a specific way of connecting a series of devices to a computer, or more precisely, a method of propagating signals along a bus. This method is a bus line that is interconnected with units in such a manner that a signal passes from one unit to the next in serial fashion. This daisy chain method of connecting devices establishes a built-in priority scheme whereby the unit closest to the CPU has the first or highest interrupt priority. öAn impact printer that prints fully formed characters one at a time by rotating a circular print element composed of a series of individual spokes, each containing two characters that radiate out from a center hub, is called a daisy wheel printer. In use, the wheel spins rapidly until the desired character is in position. Then the hammer strikes the type, forcing it against the ribbon and paper causing the character to be printed. Daisy wheel printers produce letter quality output. ®$DAT, a cassette tape for storing large amounts of data, had its origin in the audio world. DAT technology emerged in Europe and Japan in 1986 as a way to produce high quality, distortion-free audio recordings. It works by converting recorded audio signals into digital data which can be read by a computer. It provides the capability to store large amounts of information to a cassette tape both for backup purposes and for on-line data storage. One cassette containing digital tape less than four millimeters wide can store 1.3 gigabytes of data. That is approximately the same storage capacity of sixty-five 20MB fixed disks, or more than 3600 standard floppies. kA database is a set of interrelated data records stored on a direct access storage device in a data structure that is designed to allow multiple applications to access the information. A database should have minimal redundancy of data and allow for growth and change. A database is a highly structured file that attempts to provide all the information allocated to a particular subject and to allow programs to access only those items they need. The information you are now reading has been previously stored in a database. cpA database server is a microcomputer dedicated to the task of encapsulating database files and indexes, restricting access, enforcing security, and providing applications with a consistent interface to data via a data dictionary. A database server is often connected to a local area network so that its services are available to the workstations. ÌOThere are many types of Data Bus connectors such as DB-9, DB-15, DB-19, DB-25, DB-37, and the DB-50. These connectors are used for a wide variety of serial and parallel data input and output by many manufacturers. The number following the DB- refers to the maximum number of lines or wires within the connector. Not all of the wires or lines, especially on the large connectors, always have an assigned function. The DB-9 connectors are commonly used for RS-232 communications. The DB-25 connector is often found on the computer end of a parallel printer cable for PCs and a Centronics 36-pin connector is on the printer end of the same cable. But the DB-25 is also used for serial connections. çA DBMS is simply a computer program for managing the data contained in database files. A well-designed database management system allows the end user to do all of the following: define the structure of the information to be maintained; define a custom screen layout for data entry; enter data; retrieve individual records; view, edit, delete, or print individual records; rearrange records into different orders for on-screen or printed lists; select various subsets of the data for different purposes; perform calculations and store, view, or print the results; print formatted reports that present the information in the database in a form readily accessible to people who know little about computers and databases. àDCA, an abbreviation for Document Content Architecture, is a text file formatting guideline designed by IBM that enables the exchange of text-only documents between computer systems. DCA provides for two types of document formatting, RFTDCA and FFTDCA. RFTDCA, Revisable Form Text DCA produces documents with flexible formatting that can be changed by the receiver. FFTDCA, Final Form Text DCA produces documents whose formatting can not be changed by the receiver. úhThese two abbreviations are described in an EIA standard as two separate hardware devices connected by an RS-232 serial cable. The difference between the two is the wiring of pins two and three. The DCE, Data Communications Equipment, devices typically transmit on pin 3 and receive on pin 2. Examples of DCE devices: external modems, printers DTE, Data Terminal Equipment, devices typically transmit on pin 2 and receive on pin 3. Examples of DTE devices: personal computers, terminals Ø<DDE is a form of interprocess communication implemented in mutitasking operating systems such as Microsoft Windows and OS/2. Information, commands, and status information can be exchanged between two or more programs if they support DDE and are executing simultaneously. For example, a spreadsheet with a DDE link to a communications program could keep its stock prices current with the trading information received over the communications channel. An exchange of data in DDE is called a conversation and an application can participate simultaneously in multiple DDE conversations with any number of other applications. A conversation is organized around three conceptual descriptors: service, topic, and item. îWith multitasking operating systems, when multiple tasks are running, they often need access to the same peripheral devices such as disk drives, memory, printers, and other pieces of hardware. Since each task competes with others for the same resources, it's likely that, at some point in time, one task will have the resources needed by another. The operating system should manage the tasks so that the resources are properly shared. But it's possible for the operating system to allocate resources in such a way that it becomes impossible for any task to proceed. This position is known as a deadlock or deadly embrace. A deadlock is similar to a stalemate and is guaranteed to bring the operating system to a grinding halt. î_When a value, parameter, attribute, or option is assigned by a program or a system in the absence of one specified, it is called the default. Oftentimes, a computer program will contain pre-specified values that are used unless it is given alternative values. These pre-specified values are called the defaults. Some programs allow the operator a choice of two or more options. If a selection is not made by the operator, a selection is then automatically assigned, by default. • A delimiter is a special character that designates the beginning and/or the end of a field or string of characters. Examples: In the following line, both the comma and the double-quote are used as delimiters; "Sarah Peudic","14 Hospice Way","San Jose","CA","96370" In the next line, a comma is used as a data field delimiter; 813, 323, 0961, 283.40, 1128, 4915.22, 33710, 317.46 SThe number of bits or characters that can be recorded in a given length of recording surface is called the density, often expressed in bits per inch. Large computer systems and minicomputers use open reel magnetic tapes with 7 or 9 tracks or recording channels and densities of 200, 556, 800, 1600, or 6250 bits per inch (BPI). Ð4The Data Encryption Standard was designated in 1977 by the National Institute of Standards and Technology as the official method of protecting unclassified computer data both in agencies of the federal government and commercially. The DES was originally developed by IBM researchers. The DES is a single-key system, in which data is both encrypted and decrypted with the same key. The key is a sequence of eight numbers each between zero and 127. The algorithm divides a message into blocks of eight characters, then enciphers them one after another. Under control of the key, the letters and numbers of each block are scrambled no fewer than 16 times. The DES then links the enciphered blocks together in such a way that the encryption of each block, beginning with the second one, depends on the results of encoding the one that precedes it. Consequently, the final encrypted block is changed if a single character is altered anywhere in the message. v}A desktop computer is a type of microcomputer small enough to fit easily on top of a desk. It contains the microprocessor, the input and output devices, and a file storage device all in one unit. The keyboard is a detachable type and the video display is a separate unit. Desktop computers are AC powered rather than battery operated like most laptop computers. 3OA device driver is a system file or software component that contains the instructions necessary to control the operation of a peripheral device. It contains the detailed information about the device it controls. The standard device drivers are part of the operating system, and additional drivers are added as new peripheral devices are installed. For example, if a mouse or trackball is added to your personal computer, the appropriate device driver needs to be installed so that the operating system can communicate properly with it. Device drivers associated with application packages such as desktop publishing programs typically only perform the data translation. These higher level drivers rely on the standard drivers to actually send the data to the device. (printer, plotter, CD-ROM, etc.) ;,A device monitor is an operating system program or class of programs that track or monitor the data stream being processed by a character device driver. OS/2 provides such a class of programs that simplify, standardize, and enhance the process of managing TSR programs. The device monitors wait for and react to the event that triggers a memory resident program to the foreground. Since DOS was not designed to support TSR programs, a form of pseudo- multitasking, many unpleasant side effects can occur when TSRs or pop-up programs are used together. ìxThe performance of a computer system is often evaluated by measuring its operational speed in a variety of different tasks. The Dhrystone benchmark program is used as a standard figure of merit indicating aspects of a computer system's performance in areas other than its floating-point performance, for instance, integer processes per second, enumeration, record and pointer manipulation. Since the program does not use any floating-point operations, performs no I/O, and makes no operating system calls, it is most applicable to measuring the performance of systems programming applications. The program was developed in 1984 and was originally written in Ada, although the C and Pascal versions became more popular by 1989. 6&There are two main ways of doing things electronically, analog or digital. The digital method is to consider a circuit either on or off, a signal as either present or absent, with no levels in between. Electronic circuits using the digital mode are simple to design and non-critical in operation. The all-or-nothing nature of digital circuits make them immune to drift and distortion, and their simplicity makes them easy to manufacture in large quantity. Digitizing is defined as transforming a signal or piece of information into digital form. ÓsA digitizing tablet is an input device for obtaining accurate graphics input. It is connected to the microcomputer with a cable and includes some type of pointing device called a transducer. The tablet has a flat surface with a defined space, or active drawing area, where the operator can place a map, a drawing, or a menu overlay. A pointing device is then used to pinpoint areas within the work space, and the tablet sends coordinate data to the CAD application program. While a mouse reports a relative position based on its last known position, a digitizer returns an absolute location regardless of the last known position of the transducer. Compared to a mouse, a digitizing tablet is more precise and can take samples faster. Also, because the stylus and fixed surface provide for a more natural drawing motion, artists and designers prefer digitizing tablets. Tablets range in dimension from book size all the way up to drafting table size. $DIN is an abbreviation for Deutsch Industrie Norm. The DIN connector is a multiple pin connector conforming to the specification of the German national standards organization. On most IBM-compatible microcomputers, 5-pin DIN connectors are used to connect the keyboard to the motherboard of the system unit. An 8-pin DIN connector is used as the serial port connector on the Macintosh line of computers. The PS/2 line of IBM computers use a 6-pin DW connector to connect the keyboard and the pointing device. ¦`Dingbats are special graphical characters, not letters or numbers, which represent a wide variety of ideas. They are also used for decorative purposes in a document. The ASCII characters 1 and 2 (the smiling faces) are dingbats. The new Unicode has a number of codes reserved especially for dingbats. Dingbat font cartridges for desktop publishing are available. The most popular is the Zapf Dingbats font. »MDIP is an acronym for Dual In-Line Package. Printed circuit boards and peripheral devices are often equipped with a bank of DIP switches. There are two styles; slide switches and rocker switches. In both cases, the switch positions can be set on or off with a ball point pen or some other pointed object. These hardware switches allow for a variety of operating conditions to be set before the board or device is put into use. ²A directory is an area on a disk for storing files. Directories consist of files and/or subdirectories. A directory listing will show the names of files and subdirectories subordinate to that directory along with file sizes, creation dates and times. Each formatted disk contains a main directory also called the root directory. With DOS, the most common hard disk root directory is referred to as "C:\" or just "C:". «Directory hashing is an operating system technique for reducing the time spent in searching for file locations. Information about the location of disk files and all their parts is stored on the disk itself. The directory hashing process not only reads that information into memory but it also indexes it for faster retrieval. With directory hashing, the response time for disk I/O can be reduced by as much as 30%. vFiles stored on a disk are arranged in tree-structured directories. The main directory on a disk is called the root directory. It can have files and/or other directories subordinate to it. ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ The root directory has either files or subdirectories under it. ³ ÀÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÙ ÚÄÄÄÄÄÄÁÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÁÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÁÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÁÄÄÄÄÄÄÄ¿ ³ Subdirectory ³ ³ One file ³ ³ One file ³ ³ Subdirectory ³ ÀÄÄÄÄÄÄÂÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÂÄÄÄÄÄÄÄÙ ÚÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÁÄÄÄÄÄÄÄ¿ ³ One or more files or subdirectories.... ³ ³ Subdirectory ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÂÄÄÄÄÄÄÄÙ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄ¿ ³ One or more files or subdirectories.... ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ >A disk is a type of magnetic storage media. The storage capacity varies greatly from single-sided floppy diskettes to high capacity fixed disks and disk packs. A disk is the most common type of direct access storage device. The terms disc and disk are used interchangeably. 'A disk cache is a software technique of speeding data access times. Copies of recently accessed disk sectors are stored in memory to a reserved area called cache RAM. When the executing program or the operating system requests to read a sector from the disk, the disk caching software checks to see if the sector is stored in cache RAM. If it is, the sector is retrieved from RAM and returned; no disk access is required. If the desired sector is not in cache RAM, the software reads the requested sector from the disk, stores it in cache RAM, and returns it to the program. When the info is found in the cache, it's a hit. When the info must be retrieved from the disk, it's a miss. Some disk caching programs also check for sector writes. ý0Disk mirroring is the process of performing all disk writes to two separate hard disks. Both disks contain exactly the same information. The second disk is a mirror image of the first. In case one of the disks fails, this fault tolerant capability allows the system to continue to function without pause from the remaining single disk. Disk mirroring technology has been active on mainframe and minicomputers for many years and has just recently begun to appear in the world of desktop microcomputers. Disk duplexing includes the process of disk mirroring but includes redundant controller boards and cabling. It is therefore more complex and provides a greater degree of fault tolerance. Disk duplexing is performed on two separate channels. @jThe diskless workstation gets its name from the fact that it has no local floppy or hard drive available. It consists of just a monitor and a keyboard. A local printer is optional. Also sometimes referred to as diskless LANstation, this type of workstation can only be used as a node on a network. It gains access to the network through software on a ROM chip which can be located on the network interface card or built right into the keyboard. The biggest disadvantage to using a diskless workstation is that it become useless if the network is down. Some companies utilize diskless workstations as a security measure by preventing users from copying data. However, if the diskless workstation contains an expansion slot, a hardcard could be easily connected for transferring data from the file server. ñ1DIX is an abbreviation for Dec-Intel-Xerox. A DIX connector is a 15 pin connector on a Network Interface Card. As an example of its use, the Ethernet Local Area Network interface cards (NIC) have two cable connectors, a DIX connector and a BNC connector. One or the other can be used. If the BNC connector is selected, the board will use its own built-in circuitry. If the DIX connector is selected, the board will bypass the internal transceiver and use an external transceiver. ?Dow Jones News/Retrieval is an on-line service with a text-based interface founded in 1974 by the Dow Jones Co., publishers of the Wall Street Journal. It is the oldest and most respected provider of online financial information. Services include: financial news, stock market quotes, statistical data for over 1500 mutual funds, pricing, dividend, and financial data for up to 15 years on 120,000 U.S. and Canadian stocks and bonds, on-line trading, and investment research. For current fees and more information: Dow Jones Information Services 800-522-3567, Ext. 294 in Princeton, NJ dial 609-520-8349, Ext. 294 Ã]DLLs are libraries of object files available to programmers writing code for the Windows operating environment. Functions and procedures written in languages like Pascal and C can be compiled and the object file stored in a DLL. The use of DLLs allows for a high degree of customization. If a particular development language doesn't support a required function, it could be written in another language and made available through the DLL. êfAfter a sector of data has been read from a disk drive into the disk controller's onboard buffer it must be moved into the computer. This is done with a process known as DMA or (Direct Memory Access). The transfer of data takes place directly along an input/output channel at high speed between memory and the device. The CPU only initiates the transfer on a DMA request and therefore is not involved. The time required to transfer the disk sector determines how soon the controller will be ready to read the next sector. For this reason add-in Accelerator "Turbo" Cards do not generally change a machine's optimum interleave since the main system clock speed, which continues to control DMA memory accesses, is not changed. À#Documentation is a collection of written descriptions and procedures that provide information and guidance about the proper operation and maintenance of a computer program or peripheral device. For computer programs, on-line documentation is the preferred method of access to its operation and/or description. Sometimes this information is even available during the operation of the program by entering a special keystroke combination. ”VDOS is an acronym for Disk Operating System. It is an operating system for microcomputers developed by Microsoft Corp. for IBM's 16-bit machine, the IBM PC and compatibles. DOS is actually a clone or a re-write of CP/M, an operating system for earlier 8-bit computers. DOS was written for the 16-bit 8086 and 8088 microprocessors. There are almost as many varieties and versions of DOS, as there are different types of IBM-compatible microcomputers. IBM's version of DOS, maintained by Microsoft, is called PC-DOS. MS-DOS, also maintained by Microsoft, is available to clone makers using Intel's 8086 family of microprocessor chips. BAn impact printer that prints characters composed of dots is called a dot matrix printer. Characters are printed one at a time by pressing the ends of selected wires against an inked ribbon and paper. The wires are arranged in various sized rectangles. †iThe sharpness of the images that appear on your computer monitor is defined by the dot pitch. Dot pitch measures the width of the dots that make up a pixel. The smaller the dot pitch, the sharper the image. Color monitors use three dots in red, green, and blue (RGB) to focus on a single point or dot to make up a pixel. On monochrome monitors, each dot is a pixel. The accepted standard dot pitch is 31/100 of a millimeter (.31mm). The dot box is defined by having so many pixels wide by so many pixels high. Dot box examples for popular display adapters: CGA - 8x8, MDA - 9x13, EGA - 8x14, VGA - 9x16 ÜJWhen two computer words are used to store an item of data to maintain a higher level of precision, the task is said to be executed in double precision. Often an entire program is coded to run in double precision. "iBoth download and upload are relative terms referring to the process of transferring data and/or program files from one computer to another, or from a computer to a peripheral device. There are many modern computer systems that maintain large libraries of software programs. These programs can be downloaded to other computers over the telephone lines, using a modem and a communication software package which handles the protocol. On a Local Area Networks, data files and programs are downloaded and uploaded to the file server. qDRAM is an acronym for Dynamic Random Access Memory. It is a memory chip in which data is stored capacitively and which must be energized or recharged hundreds of times a second or the data will be lost. While DRAM is being refreshed, it cannot be read by the processor. If the processor attempts to read the DRAM while it is being refreshed, one or more wait states occur. DRAMs offer high bit densities, low cost, input/output compatibility with TTL levels, and speed compatibility with most microprocessors. The operational speed of DRAM chips is measured in nanoseconds, such as 150, 120, 100, and 80ns. QDesktop Publishing is the art of using a personal computer to merge text and graphics files to produce high-quality output usually on a laser printer. It requires a desktop publishing software package, a powerful personal computer with a hard disk, and a graphics-based monitor that can display one or two full pages at a time. The text files are often created using word processors or text editors while the graphics files are created with CAD software or paint and draw programs. Scanners can also be used to capture graphics files from pictures, drawings, and photographs. Both text and graphics files can then be copied into the desktop publishing system for merging, editing, and output. Examples of popular desktop publishing programs: Aldus PageMaker Ventura Publisher The Office Publisher Legend PFS: First Publisher GEM Desktop Publisher äTerminals, or workstations with a video screen and keyboard, were used for many years before microcomputers to provide for the input and output of data to and from mainframes and minicomputers. The term "dumb terminal" came into use about the same time that microcomputers began to proliferate. As microcomputers became more and more powerful, terminals continued to provide the same services, they could not perform any stand-alone processing. Hence, they are referred to as "dumb terminals" to distinguish them from the more capable and smarter microcomputers that looked very similar. Microcomputers now can execute programs that emulate most kinds of terminals such that the host computer cannot tell the difference. SA dump is a copy of the contents of storage locations in main memory at a specified point in time. A dump can be recorded on paper, to tape, or to a file to be used for debugging purposes. This example shows a dump of memory starting at address 0000:0000 ÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜÜ 0000:0000 E8 4E 37 01 33 FF 0F E5 00 F0 33 FF 00 F0 N7 3 3 0000:0010 33 FF 00 F0 54 FF 33 FF 00 F0 33 FF 00 F0 3 T 3 3 0000:0020 95 E6 00 F0 26 01 33 FF 00 F0 33 FF 00 F0 & y53 3 0000:0030 33 FF 00 F0 BE 01 57 EF 00 F0 33 FF 00 F0 3 W 3 0000:0040 65 F0 00 F0 4D F8 41 F8 00 F0 69 02 79 35 e M A i 0000:0050 39 E7 00 F0 59 F8 8A 01 79 35 0B F9 00 F0 9 Y y5 0000:0060 00 00 00 F6 4E 01 D3 05 84 38 F2 00 EF 07 N 8 0000:0070 FE 01 79 35 A4 F0 22 05 00 00 33 FF 00 F0 y5 " 3 0000:0080 C3 12 37 01 59 01 2F 01 D7 22 3C 01 D7 22 7 Y #/ "<" ßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßßß úaThe Digital Video Interactive technology combines motion video, still pictures, multitrack audio, and computer graphics, into a single integrated environment controlled by a personal computer. Implemented by DVI boards and chip sets, the goal of DVI is to eliminate the expense, complexity, and awkwardness of a part-analog and part-digital system by storing and processing everything as digital data. DVI was conceived by Larry Ryan of the David Sarnoff Research Center (RCA Laboratories) in 1983. The DVI project and technology was acquired by General Electric when RCA dropped out of the videodisc and home computer business. Today, Intel Corporation owns the DVI technology and will soon be mass producing DVI boards and DVI chip sets. …Designed by August Dvorak, patented in 1936, approved by ANSI in 1982, the Dvorak keyboard provides increased speed and comfort and reduces the rate of errors by placing the most frequently used letters in the center for use by the strongest fingers. In this fashion, finger motions and awkward strokes are reduced by over 90 percent in comparison with the familiar QWERTY Keyboard. The Dvorak keyboard has the five vowel keys, AOEUI, together under the left hand in the center row, and the five most frequently used consonants, DHTNS, under the fingers of the right hand. Some businesses are requiring their keyboard personnel to use this system. Also, several computer companies are now manufacturing keyboards with a switch that will change from one keyboard design to the other. There are also TSRs with keyboard macros to convert your present keyboard to the Dvorak style. ¹~Extended Binary Coded Decimal Interchange Code is a standard 8-bit code for the representation of characters. It allows 256 possible character combinations and stores one alphanumeric character or two decimal digits within a single byte. EBCDIC is the standard code on IBM mini-computers and mainframes, but not on the IBM microcomputers, where ASCII is used. EBCDIC, pronounced "ebb-sa-dick", is an alternative to ASCII Code. FKWhen data is being transmitted, the receiving device often re-transmits the information back so that the originating device can be sure it was received correctly. On a telephone line, there is a device called an echo suppressor that blocks the listening side while one person is talking in order to eliminate echoes. +/An edge connector provides a means of interconnecting two printed circuit boards. The connector consists of a row of etched lines on one side or edge of the board that is to be plugged into another board. The motherboard or system board in most computers has a number of expansion slots for add-on boards. The add-on boards with their edge connectors plug into the motherboard. All of the following examples of add-on printed circuit boards or cards utilize edge connectors: Internal modems, video cards, hard disk controller cards ÅCOne of the major problems associated with electronic mail is the linking of different systems together to speed the movement of information that gets put into forms, like invoices, order forms, bills of lading, etc. As more and more organizations implement and link networks of computers, the need for exchanging information with other organizations will continue to increase and updated universal addressing schemes will be required. The Electronic Data Interchange System addresses this problem and allows for the exchange of business information between companies. EDI keeps track of inventory and allows customers to re-order from their suppliers electronically, from computer to computer.  As the term suggests, EFT refers to financial transactions that originate at a terminal or microcomputer and cause the exchange of money from one bank account to another. This type of convenient banking is expected to become more and more popular as the number of home computers grows. In order to take advantage of this service from home, your computer must be equipped with a modem for dialing-out. One of the most successful EFT programs for microcomputers is CheckFree from CheckFree Technologies, Inc. in Columbus, Ohio. pAn Enhanced Graphics Adapter is an IBM video display adapter that can be used with color and enhanced color displays. It also provides a monochrome graphics mode. In color it can produce characters in a dot box of 8 by 14 pixels when used with an enhanced color display. The EGA operates at a horizontal scan rate of 21.85 MHz, and can display 16 colors from a palette of 64 at a resolution of 640 by 350 pixels. To be fully EGA compatible, a video display monitor must have a bandwidth of at least 16 MHz. °~The Industry Standard Architecture (ISA) for IBM-compatible microcomputers defines the use of the data bus and the 8-bit and 16-bit expansion slots on the PC-XT and PC-AT models. EISA is the Extended ISA. The EISA consortium led by Compaq Corporation and joined by almost all microcomputer manufacturers except IBM, was formed in 1988 to offer an alternative to IBM's Micro Channel Architecture (MCA). The issue concerns non-IBM system and board manufacturers because the MCA does not provide upward compatibility with existing machines. With an EISA bus, 8- or 16-bit add-in boards based on the Industry Standard Architecture (ISA) can be fitted to the new machines. HjA typical ElectroLuminescent display consists of a thin film of EL material (phosphor) sandwiched between thin films of insulating dielectric material. The front material is transparent, while the rear material is reflective. The zinc-sulfide-with-manganese phosphor emits a bright yellow light when subjected to approximately 200 VAC. The voltage is applied via a grid of electrodes, each pixel of which can be individually switched on. Other phosphors can be used for different colors. EL displays offer better contrast and broader viewing angles than gas-plasma and LCD displays. They use more power than LCDs but less than gas-plasma and considerably less than CRTs. They are the most rugged type of display and are more reliable than CRTs. EL displays are still offered primarily in monochrome configurations. RXThe following acronyms are frequently used to save time and bytes during on-line conferencing in electronic forums and in E-mail. BTW - By The Way FWIW - For What It's Worth g,d&r - grinning, ducking, and running IMCO - In My Considered Opinion IMHO - In My Humble Opinion OTOH - On The Other Hand OIC - Oh, I See! PITA - Pain In The Arse PPN - Programmer Project Number or a CompuServe User's ID#. RSN - Real Soon Now ROF,L - Rolling On Floor, Laughing RTFM - Read The Friggin' Manual WYSIWYG - What You See Is What You Get Ç Electronic mail systems allow computer users to exchange information quickly and easily on a network of computers. The most sophisticated electronic mail systems provide a wide array of transfer functions for the exchange of documents, binary files, graphics, and even such exotic data as voice messages and video images. There are three major segments of the E-mail industry: LAN-based, PC users on a single or multiple local area network. Host E-mail, runs on mainframes and minicomputers as an important component of office automation. Public E-mail is provided by communications-oriented companies and it is accessible with a modem over telephone lines. On a Local Area Network (LAN), read and write requests for data are by far the most common requests made by workstations to the file server. Program files and data files both reside on the network disk and must be disbursed on demand to the workstations. Overall file server performance can be greatly affected by how well the server responds to these requests for data. "Elevator seeking" is a separate disk read process that is responsible for reading data from the file server's hard disks and placing them into cache buffers. Incoming requests are sorted into an order of priority based on the disk drive's current read/write head position. This technique optimizes disk head movement and results in significantly higher disk throughput under loaded conditions. –+Embedded commands are codes that are placed within a file to control a hardware device such as a printer. In word processing, embedded commands are used to send instructions to a printer for changing the print characteristics, such as the font. There is no standard for these commands. They vary from one application to the next. An embedded system is a specialized computer system designed to control the unit in which it is housed. It is custom programmed for a specific task and usually consists of both system and application software functions. Embedded systems are contained in guided missile systems, rockets, and space vehicles. Ì?An emoticon is a figure created with the symbols and punctuation characters of a computer keyboard and are used to convey the spirit in which a line of text was typed. :-) An emoticon is an acronym created from the terms "emotion and icon". Tilt your head slightly to the left to read the following emoticons. :-) or :-> Grin, happy face :-( Unhappy 8-) Smile with glasses :-O Shout :*) Clowning around <:-) For dumb questions =|:-)= Uncle Sam @>--->---- A rose. Other emoticons often appear in electronic forums and E-mail. If you encounter one not shown here, and need an explanation, call us. I]This specification provides a way for microcomputers running under DOS to access additional memory. It was developed by Lotus Corp., Intel Corp., and Microsoft Corp., (also called the LIM Spec). Systems can use memory expansion boards and application software that follow this specification to enable programs to handle memory or RAM beyond the 640K that MS-DOS handles conventionally. The EMS 3.2 memory management software can simultaneously access four 16K pages at a time on up to 32 MByte of expanded memory on expanded memory boards through a 64K window in conventional memory. The Enhanced EMS (EEMS) was developed by AST Research, Ashton-Tate, and Quadram Corp. It was an upward compatible enhancement to the LIM Spec or EMS 3.2, whereby EEMS boards and compatible programs can devote a larger amount of conventional memory to the window used to access expanded memory, resulting in more potential expanded memory. EMS Version 4.0 type memory can map multiple pages of varying size into conventional memory enhancing both data access and program execution capabilities. ÓZA device which has been given a signal that permits it to function is said to be enabled. The opposite of enabled is disabled. Software commands can be issued to enable or disable peripheral devices. 6 The ultimate user of the output produced by a program or a system is called the end user. You, the consumer, are the end user of the software and hardware that you purchase. You are the end user of this PC-GLOSSARY. If you have any suggestions for improvements, please contact Disston Ridge, Inc. I_The best quality graphics are vector graphics where the image is made up of lines, curves, and filled regions rather than a series of data points as in bit-mapped graphics. EPS stands for Encapsulated PostScript, which refers to a condensed graphics file containing actual PostScript language in a special format. EPS files can become quite large, and some contain a bit-mapped image of the graphic so that if the output is sent to a non- PostScript printer, the bit-mapped image is used, but to get the best results, EPS files should be output on a PostScript device. ÑErgonomics is the study of human posture and proportion in order to design furniture and equipment that can be used comfortably and without strain. It is frequently called human engineering, and emphasizes the safety, comfort, and ease of use of human operated machines, such as computer workstations. Tangible results of ergonomics are the addition of numerical keypads on standard keyboards, and tilt/swivel bases for non-glare video display screens. œWIn conjunction with the ANSI.SYS Device Driver, a DOS system software program, escape sequences can be used to add a great deal of useful or merely entertaining information to the display screen. An escape sequence usually has the following four elements: The Escape character, a left bracket, a numeric parameter, and a terminating code indicating the function of the sequence. For example, a sequence to set the cursor at the upper left corner of the screen takes the form ^[[1;1f where 1;1 is the horizontal and vertical position of the cursor, and f is the code telling ANSI.SYS that this is the horizontal and vertical position sequence. èFEnhanced Small Disk Interface is a hardware standard developed by a consortium of 22 disk drive manufacturers. The ESDI provides for a maximum data transfer rate to and from a hard disk of 10 megabits per second and can manage disk drives with up to one gigabyte of storage. An ESDI hard disk controller card (ie. the circuitry that controls a hard disk's operations) can only be used with a hard disk that has an ESDI interface. See the Table "Disk Data Transfer Rates" ÖzEthernet is a type of network topology which breaks the data into sealed and addressed packets, delivering them across the cable to the recipient workstation, and confirming delivery. A network supporting Ethernet transfers data packets using coaxial, twisted pair, or fiber optic cabling. Two kinds of coaxial cable are used, thick and thin. Most adapters these days include an on-board transceiver for thin Ethernet. Developed in the late 1970's by Bob Metcalf at Xerox Corporation, and endorsed by the IEEE, Ethernet is one of the oldest LAN communications protocol in the personal computing industry. It is also one of the fastest, running at 10 megabits per second. However, on a network using Ethernet, if two workstations attempt to transmit or receive data at the same time, a collision occurs and the data must be transmitted again. Data transmission is supervised by a protocol called CSMA/CD, Carrier Sense Multiple Access / Collision Detection. The process of carrying out the operations specified in the instructions of a program is referred to as program execution. In the DOS environment computer program files, sometimes called executable code, are given filename extensions of .EXE or .COM. Execution time can refer to one of three periods of time: û The time required to fetch, decode, and execute an instruction. û The phase during which a program is being executed. û The time it takes for a program to run from start to finish. ÖXWith microcomputers operating under DOS, the amount of memory that can be utilized for working programs and data, without the use of extended or expanded memory, is 640 kilobytes. Expanded memory refers to memory that acts as a pool which can be mapped into one or more conventional memory areas. Unlike extended memory, expanded memory is available for all processor types. It requires a special device driver and conforms to a standard developed by the Lotus, Intel, and Microsoft Corporations. The standard is called the LIM Spec or EMS, or EEMS, or EMS 4.0. Expanded memory works with a bank-switched memory board, the EMM, Expanded Memory Manager, and an application program that knows how to use it. ™On the main circuit board or motherboard of a computer, there are expansion slots or receptacles into which other printed circuit boards can be plugged. Since they are connected to the computer's address bus, the number and type of expansion slots determines how a system can be enhanced with additional peripheral devices or memory boards. On the IBM-compatible microcomputers, there are three different types of expansion slots. The 8-bit slots are found on all the XT models. The AT-style computers utilize both the 8-bit and 16-bit slots. The new 80386 machines can utilize the 32-bit slots as well as the 8-bit and 16-bit expansion slots. }With microcomputers operating under DOS, the amount of memory that can be utilized for working programs and data, without the use of extended or expanded memory, is 640 kilobytes. Extended memory is available only with the 80286, 80386 or the 80486 CPUs and refers to memory above 1 megabyte. It is directly addressable in protected mode. Under DOS, RAM disks or virtual disks can be created in extended memory but not used for processing. Extended memory is best utilized by operating systems running in protected mode, such as UNIX or OS/2, or by operating environments running with DOS such as Windows or DESQview. Introduced in 1988 by Western Digital and Columbia Data Products, FASST is a software specification that allows developers to easily interface their hardware devices to a SCSI interface and to operate those peripherals under a number of operating systems. FASST implements a SDLP interface and its software handles the handshaking between the peripheral and the attached SCSI adapter. Thus a peripheral can be developed that makes system calls to the FASST software, which in turn handles interfacing to the board. This approach solves two problems: It allows a user to upgrade from an 8-bit to a 16-bit SCSI adapter without worrying about incompatibilities. It also allows devices attached to the SCSI adapter to be run under DOS, Unix, Windows, NetWare, and OS/2. &The File Allocation Table is a system area on a disk that keeps track of disk clusters allocated to all the files on a DOS partitioned disk. The FAT also keeps track of available disk space. In the case of a hard disk, the size of the FAT limits the amount of storage capacity that can be handled under DOS. With DOS 3.3 and earlier versions, hard disks are limited to 32 megabytes of storage. Hard drives with more than 32 megabytes of available storage can be partitioned into small segments. These higher-capacity hard disks come with special drivers that modify the FAT thereby allowing DOS to use the additional storage space. NsA fault tolerant computer system is designed to provide continuous operation in the event of a failure. Such a system consists of redundant components and processes that are designed to immediately replace any failed component. Totally fault tolerant systems not only require backup power sources but also imply a duplication of systems in another distant location in the event of a natural disaster or act of vandalism. Fault tolerant computer systems are widely used in the finance industry for operations such as stock market transactions and on-line banking functions. ¾"A FAX board is an add-in printed circuit board for a personal computer that allows the system to send and receive text and graphics data over the telephone lines. A FAX board is actually a facsimile machine in a personal computer. FAX boards communicate via the CCITT Group 3 standard using a modem at 9600 bits per second, half-duplex, and include a data compression scheme to speed data transfer times. Transmission time varies depending on the compressibility of a given page, but it typically ranges from 30 to 60 seconds. On poor quality telephone lines, the FAX modem will drop back to 7200 bps, then 4800 bps, and then even 2400 bps to allow the data to transfer error free. „vFacsimile communication has been around much longer than electronic computers. In fact, its origin can be traced to 1842 when a Scots clockmaker named Alexander Bain made the first machine capable of transmitting crude images for short distances over telephone wires. The advancement of digital technology has replaced the older, slower analog fax machines with faster, cheaper, easier-to-use facsimile machines that can transmit pictures of original documents. Almost anything on paper can be sent from any telephone to another telephone in about one minute. Facsimile transmission can be done from your personal computer and is essentially a kind of electronic mail that can transmit to and from any place in the world at any time of the day or night, on weekends or holidays. The only requirement is two facsimile machines or boards connected by an ordinary telephone line. _lBeginning in 1978, in answer to some specific complaints of interference to radio communication, the Federal Communications Commission began a painful rulemaking procedure which resulted in new regulations regarding Computing Devices. The legal responsibility for compliance with the rules rests on the shoulders of the company which integrates the various parts of the computer system which is sold to the end user. For regulatory purposes, the FCC has defined two categories of computing devices, Class A and the tougher Class B. Class A Computing Devices are those marketed for use in a business, commercial, or industrial environment. Class B Computing Devices are those marketed for use in a residential area; Personal Computers, electronic games, electronic organs, etc. REF: FCC Regulations, CFR 47 Part 15 Subpart J, Computing Devices ªeThe American National Standards Institute (ANSI) has defined a new standard, FDDI, for local area networks using fiber optic cable. FDDI is very close to the IEEE 802.5 standard and uses an architecture similar to that of IBM's Token Ring. FDDI can support very large LAN's, up to 500 nodes within a 100 kilometer (62 mile) circumference, and data transfer rates up to 100 megabits/second. A key to FDDI's high performance is its use of 1300 nanosecond wavelengths to optimize the fiber's bandwidth. It also needs no special repeaters, amplifiers or other signal-conditioning equipment, since it employs commonly available fibers and electro- optical components. ‡oOne femtosecond is one quadrillionth of a second, or a millionth of a billionth. There are as many femtoseconds in one second as there are seconds in thirty million years. There are 1,000,000,000,000,000 femtoseconds in one second. The combining form 'femto' is derived from the Danish word femien for fifteen. Femto is used to designate 10 to the minus fifteenth power. 7=Fiber optics is the technology of transmitting data over communication lines made from flexible strands of glass or plastic through which laser beams or light from LEDs are passed to transfer data. The strands are formed into cables and can carry many more times the amount of data than traditional copper wire. Fiber optic cable, although it does not improve transmission speed, can send data over great distances. Radio transmitters, arc welders, and noisy fluorescent lights have no effect on the light pulses traveling inside fiber optic cable. Ê.An acronym for First In - First Out, FIFO is a programming method of storing and retrieving items from a list, table, or stack, such that the first element stored is the first one retrieved. An acronym for Last In - First Out, LIFO is a programming method of storing and retrieving items such that the last item in is the first one retrieved. Push-down list is a list written from the bottom up, with each new entry placed on the top of the list. The item to be processed first is the one on the top of the list. A push-down stack is a set of memory locations or registers in a computer that are accessed via the LIFO method. Most microprocessor program stacks operate on the LIFO method. The next generation of computers, predicted to be in use before the year 2000, will be referred to as fifth generation computers. Their increased computational power is expected to result from parallel processing or the ability to process several programs at the same time. They are expected to be true knowledge systems, able to combine one set of facts with other sets to produce sophisticated new solutions. No other computer has yet accomplished that task. To play the central role in society that present day scientists envision, these machines will need to be easier to use and will understand spoken, written, and graphic input. ^;A file is simply a recording of information. Computer data and programs are stored on floppy diskettes, hard disks, or tapes in a manner very similar to the way your voice is recorded with a tape recorder, magnetically. A complete collection of related data is a file, an example would be a mailing list file. One complete unit of the information in a file, is called a record. In the mailing list file example, all the information connected with one address would be a record. Within a record, are fields. The zip code would be one field, in an address record, in the mailing list file. J;The term "compression" means to reduce in size. Computer file compression is achieved with an archiving program. Files are quickly reduced in size. This process, sometimes called ARCing, creates archive files which have three distinct benefits: They use less disk space than normal files. Archive filing increases the life and storage capability of your expensive hard disk. Many individual files can be stuffed into a single archive file. This makes file group identification, copying, and transporting faster and easier. Archived files travel faster via modem which reduces telecommunication transmission and reception. Many BBS (computer bulletin board services) use archived files as a means to store more files with easier access to them by way of speedier communications. qFCB is an abbreviation for File Control Block. Information about the status of a file is maintained by the operating system in a block of data called a File Control Block. FCB's are used by programs to provide the name and identification of opened files and their status while in use. With DOS, the traditional file services are based on FCB's. An alternative to the FCB-oriented file services works with a 2-byte number or 'handle' that uniquely identifies each file that is in use by a program. gOn a network of microcomputers, one of the workstations serves as a hub of information. This workstation, known as the file server, can be dedicated to its task of storing community files or it can be designated as non-dedicated in which case it can also be utilized as a workstation on the network. Serving as the hub of the network, the file server also runs the network operating system software for controlling access to the network, and managing the electronic messages and file transfers of the network. As the number of workstations increases above four or five, so does the importance of having a file server that is dedicated to the task of managing the network. With non-dedicated file servers, just the presence of a user application will degrade its performance. And if the user application hangs, so does the network operating system. êyIn DOS, filenames are from 1 to 8 characters long and can be followed by an optional short name called an extension. An extension starts with a period, has 1, 2, or 3 characters, and follows immediately after the filename. The following are examples of extensions used to identify the type of data or the format of data to be found in the file. .EXE Executable program, loaded to a specific memory location. .COM Executable program, stored as an image of the program as it appears in memory. .BAT A batch file consisting of a series of commands .SYS A system file, often a device driver .TXT Often an ASCII text file created with a text editor See the table "Filename extensions" for more examples. %Firmware is a combination of hardware and software designed for a specific task. It is a program and/or data stored on a ROM chip that helps control the operation of a computer. Firmware is non-volatile memory, which means that it retains its contents even when the power is off, for storing information. Electronic calculators contain firmware with the instructions for performing the various mathematical operations. The ROM BIOS chip in a microcomputer is an example of firmware. PROM's, EPROM's, and EEPROM's are firmware. ^tA computer of the first generation is classified as beginning around 1951, characterized by physically large units using vacuum tube circuitry, stored programs, and mostly magnetic tape for auxiliary storage. The UNIVAC I was a first generation computer, commercially available in 1951. First generation computers are now museum pieces. ûA disk or disk pack that is permanently mounted on a disk drive is called a fixed disk. Although fixed disks are most often found on large scale computers, the hard disks found on personal computer systems are also referred to as fixed disks. ³\Fixed point refers to a number system or a method of storing and calculating numbers where the decimal point is always in the same location for a particular quantity. Desk calculators operate with fixed point numbers. The operator is expected to keep track of the decimal point. Contrast with floating point arithmetic, which is a method of calculation that automatically accounts for the location of the decimal point. C?A software term, a flag is a variable used in a program to indicate whether a condition has or has not occurred. A flag variable could be used to indicate that a record was found to have an error in one of its fields. A flag mechanism is used to define access privileges to a network directory or subdirectory. ÜIntroduced early in 1989 by Intel Corporation, the flash EPROM as a new type of memory chip combines the flexibility of RAM with the permanence of disks. Flash EPROMS do not need a supply of back-up power to retain data and can be packaged like regular EPROMS and DRAM chips. It may be possible someday to replace the bulky, power-sapping disk drives in computers with varieties of flash EPROMS. Laptop computers are expected to take first advantage of these new chips. One megabit chips were selling in 1990; two and four megabit chips were available in 1991. When 16-megabit chips arrive in 1994, vendors could introduce 32 MByte and 48 MByte "hard drives" on a flash EPROM card roughly two by three inches. aA data file that does not physically interconnect with or refer to another file is called a flat file. Flat files stand alone and may be created in a variety of ways. In a relational database management system, flat files refer to non-interconnected files. ½vFloating point arithmetic is a method of calculation that works with number quantities that are represented by a number called the mantissa and by a power of the number base, or exponent. ÚÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ MANTISSA ³ EXPONENT ³ ACTUAL NUMBER ³ ÃÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ ³ 283451 ³ 0 ³ 283451.0 ³ ³ 283451 ³ -1 ³ 28345.1 ³ ³ 283451 ³ -3 ³ 283.451 ³ ÀÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ The actual number is obtained by multiplying the mantissa times a power of the number base. Notice how the decimal point floats in the examples shown above. ž(FPU is an abbreviation for Floating Point Unit or processor. It is a chip designed to perform arithmetic operations. On microcomputers it may be in the form of a separate co-processor chip or it may be part of the Central Processing Unit (CPU). The Intel 80486 CPU has a built-in FPU. On minicomputers and mainframes, the FPU is sometimes housed in a separate machine often called an array processor. ;:A floppy disk is made of a flexible piece of mylar and coated with a material that can be magnetized to store bits of data. The most common size floppy disk is 5.25 inches in diameter and is often used with personal computers for storing data and programs. Floppy diskettes may be single-sided or double-sided, depending on whether they are recorded on one or both sides. Single-sided diskettes are now obsolete. On a double-density diskette there are 40 tracks of data; 80 on a quad-density diskette. High-capacity diskettes have the same number of tracks as quad- density, but they go one step further, they pack 15 sectors into each track, instead of the customary 8 or 9. The floppy disk was invented and patented by Dr. Yoshiro Nakamats. See the table "Floppy Disk Specifications" for an overview. ´CFloptical disk drives for microcomputers read and write 3.5" diskettes using a SCSI adapter. They are designed with a dual-gap read/write head with one gap dedicated to the new floptical diskettes while the other gap reads and writes standard 3.5" diskettes, both densities. These drives typically out-perform standard 3.5" drives by three times. The floptical diskettes have a storage capacity of 21 megabytes which is achieved by combining patented optical servo positioning tracks and magnetic recording technologies. The diskette media is barium ferrite, a cost-effective medium for high density recording. The Floptical Technology Association was formed in June of 1991. WFlow charting is the traditional way of diagramming programs. Instructions are written into rectangles, and decision points or branches are represented by diamond shapes. Lines connect them together, showing the flow of control from one part of the program to another. Flow charts are helpful in visualizing how a program works. Z%The dictionary defines folio as a leaf of paper, folded once so that it forms two leaves, or four pages. It also refers to a set number of words considered as a unit. In this database, the term folio refers to an idea-sized chunk of text which generally expresses a single idea, or the definition of a computer-related term or acronym. .A font is a complete assortment of print characters for a single typeface in a single size. For example, 12-point Helvetica is a different font than 10-point Helvetica. Impact printers have interchangeable fonts for different character types and sizes. On bit-mapped display systems and laser printers, the software can define a number of different typefaces or fonts. A font is different from a typeface. A typeface is the design of a particular set of letters, symbols, numbers, and punctuation marks. For example, Helvetica, Times, Palatino, and Optima are typeface families. Each family can have a number of different typefaces such as Times Roman, Times Bold, Times Italic, which share the same underlying characteristics, but require a separate design for each weight or slant. vOne footlambert equals 1 divided by pi candela per sq.ft. A footlambert (FL) is the unit for measuring the screen luminance of the video display. A candela is the modern measure of luminous intensity, roughly equal to the light given off by a candle. ,Formatting is the process of preparing a disk so that the operating system can find the sectors on each of the disk tracks. Formatting also establishes the File Allocation Table. A disk can not be used until it is formatted. Hard disks must be initialized or "low-level formatted" before they can be formatted. The low-level format sets up the sectors on a hard disk and maps the bad areas for the operating system to avoid. This process of low-level formatting is also called initializing, physical formatting, or absolute formatting. ‰yAn acronym for FORula TRANslator, FORTRAN is a high-level programming language for programs dealing primarily with mathematical formulas and expressions, similar to algebra and used mainly in scientific and technical applications. FORTRAN is one of the oldest languages but is still widely used because of its compact notation, the many mathematical subroutines available, and the ease with which arrays, matrices, and loops can be handled. FORTRAN was written in 1954 by John Backus at IBM and the first successful FORTRAN program was executed by Harlan Herrick. Microsoft FORTRAN Version 5.1 was released in the summer of 1991. WA computer of the fourth generation is characterized by physically small, lower cost microcomputers using microprocessors and memory chips. There is disagreement as to whether this is a new generation or merely an advanced stage of the third generation. ûFractal geometry is a nascent branch of mathematics dealing with irregular, convoluted, or fragmented shapes that evoke a pattern. It was made possible by the marriage of the computer and high- resolution graphics. Fractals bear a striking resemblance to structures found in nature such as cloud formations, jagged mountain peaks, the leaves of ferns. A spectacular example of fractals is the Mandelbrot set, named for its creator Benoit Mandelbrot, the acknowledged father of fractal geometry. ;8Fractional T-1 is a term which describes a digital communication service provided by one or more of the 24 channels of a full T-1 line. It is a subset or fraction of the full T-1 line. With fractional service, both the customer and the carrier company benefit. The customer is relieved of the cost of a full T-1 line and with multiple customers sharing one line, the carrier company avoids wasted lines. As a customer, whether you use full or fractional service, the physical installation is the same. See the definition of T-1 for further information. ‰8In a multiprogramming environment, when memory locations not being used are grouped together in such small numbers that they cannot be used to store pages from other programs, main memory is said to have become fragmented. A disk can also become fragmented with small gaps between files. Fragmentation is an undesirable condition and should be remedied to free-up the unused spaces. xkAs a type of freely-distributed software, freeware is a program placed in the Public Domain. It may be freely copied and passed on to others, with or without restrictions, but unlike user-supported software, each user is not expected to register with the author nor pay a usage fee. Often the author will include a request for comments on the value of the program. Ÿ=FTAM is a standard specification for transferring data between computers from different vendors. In addition to basic file transfers, FTAM has several options, such as reading and writing from indexed files, locating and erasing data from indexed files, retrieving complete information on file storage properties, retrieving file security properties, and sending and receiving file directory information. ÀdThe term full-duplex designates the transmission of data in two directions at the same time as from a terminal to a computer or from the computer to the terminal. Full-duplex (FDX) is simultaneous two-way communication. The term half-duplex (HDX) designates the transmission of data in either direction but only one direction at a time. Simplex pertains to a communications link capable of transmitting data in only one direction. <On personal computer keyboards, there is a set of numbered keys called the function keys. On most keyboards, there are either ten or twelve keys labeled F1 through F10 or F12 which are used to send different special purpose commands to the program in control. Function keys can be programmed to work by themselves or in conjunction with the Control, Alt, and Shift keys. Some commercial programs, such as word processors, have plastic templates to place over the function keys to identify their special purpose. Š$The modern practice in C-Language programming whereby a function is more completely defined, initially, using declarators that include information about the function parameters is referred to as function prototyping. In other words, when a function is initially defined, each parameter is given a name. This approach, as opposed to omitting the parameter names, allows the 'C' compiler to check the numbers and types of the parameters in actual calls to the function, and to perform proper conversions when possible. The usage of function prototypes aids greatly in tracking down programming errors and enhances code documentation. @<Fuzzy logic provides an approach to approximate reasoning where the rules of inference are approximate rather than exact. Fuzzy logic is useful in manipulating information that is incomplete, imprecise, or unreliable. Also called fuzzy set theory, fuzzy logic extends the simple Boolean operators, can express implication, and is used extensively in Artificial Intelligence (AI) programs. In the 1960s, Lotfi A. Zadeh, the father of fuzzy logic published papers describing the idea and concepts of fuzzy logic. Reference: AI Expert magazine, March 1992 issue. gYGas-plasma displays operate by exciting a gas, usually neon or an argon-neon mixture, through the application of a voltage. Gas- plasma displays use tiny pixels of gas to produce visible light, and therefore require no backlighting. When sufficient voltage is applied at the intersection of two electrodes, the gas glows an orange-red. Originally, gas-plasma technology provided only on-off control. Recent advances have improved control over the brightness of the pixels and provided several steps between the dimmest and the brightest conditions thereby offering both 4 and 16 step "grey" scales. ‹:A gateway provides an interconnection between two networks with different communications protocols. A gateway is a simultaneous interpreter between computers that speak different "languages". Gateways operate at the 4th through 7th layers of the OSI model. The gateway, which is provided by an adapter card in a workstation, enables the network to perform as if it were a mainframe terminal connected directly to the mainframe. Examples: A PAD, packet assembler/disassembler, is a device used to interface non-X.25 devices to an X.25 network. The PAD serves as a gateway. Protocol converters are gateways between networks. TGGEDCOM, an acronym for Genealogical Data Communications, is a data file format for transferring information between genealogical computer programs. The GEDCOM standard was defined and is maintained by the Family History Department of the Church of Jesus Christ of Latterday Saints (LDS). Their large Ancestral File database accepts input and produces output in the GEDCOM standard format. The purpose of the Ancestral File database is to help families and historical organizations coordinate research and reduce duplication of effort in the process of collecting genealogical data. GEnie is an on-line service, a division of General Electric Company. It claims to be the world's largest on-line teleprocessing center. GEnie is a mainframe text-based system, organized in a hierarchy of menus. Services include: libraries of downloadable software, electronic mail, conferences called round tables on computer-related topics, multi-player games, and research capabilities. For current fees and more information, GE Information Services, 800-638-9636 401 N. Washington Street Rockville, MD 20850 šiGIF is an abbreviation for Graphics Interchange Format, it is pronounced 'Jiff'. Early in 1987, CompuServe's graphics engineers introduced this remarkable new protocol as a standard for exchanging raster-based images among various computers. Some intriguing points about GIF are: It looks to future technology by being able to preserve images with a resolution of 16,000-by-16,000 individual dots or pixels. While GIF can handle up to 256 simultaneous colors, the software makes the best use of a computer's own capabilities. GIF uses a sophisticated data compression method to reduce the file size to less than half, saving in download time. +One Gigabyte equals 1 kilobyte times 1 megabyte. That's 1,073,741,824 bytes, or (2 to the 30th power). 'Giga' is a binary analog to the U.S. decimal unit 'billion' The 80286 microprocessor can access 1 GByte of virtual memory. Compact disks (CD's) have storage capacities of over a gigabyte, that's the equivalent of fifty 20-megabyte hard disks. A tape back-up system that claims to have the storage capacity of 2.2 gigabytes could easily make a copy of a 2000 megabyte hard drive. See the Conversion Table "Bytes to Terabytes" -NGarbage-In, Garbage-Out is a phrase that refers to the process of submitting invalid or incorrect data to a computer program and obtaining output results that are also incorrect or meaningless. In the early days of computing, when people were so impressed with the calculating power and speed of computers, they oftentimes too quickly accepted the output of a computer program as being almost unquestionably correct. The phrase "garbage-in, garbage-out" caught-on in the data processing field as a quick way of explaining the true situation. ‡ZA glitch is a popular term used to describe a temporary or random malfunction in hardware, caused by a noise pulse or stray signal. It causes a momentary deviation from normal operation. Problems in the software that are easily reproducible are called bugs. But when software bugs are not well understood and not frequently encountered, they are sometimes referred to as glitches. The term global denotes a complete or comprehensive coverage of a topic or operation. In computer programming, variables can be globally defined so that they can be referred to from any module or routine within a particular program. During the use of a text editor or word processor, every occurrence of a specified character or character string throughout the entire text file or document can be replaced or deleted. This is referred to as a global edit. A global backup operation makes a copy of a complete disk. In a spreadsheet program, a global format can be designated to apply to every cell of the worksheet. ˜QVersion 1 of GOSIP, the Government Open Systems Interconnection Profile was promulgated as a United States federal government information processing standard in August of 1988. Beginning in August of 1990, all communications equipment sold to the federal government had to comply with the GOSIP specification, which is a subset of the OSI network model. The main features specified by GOSIP 1 are the ability to send and receive E-mail using MHS, and to access and transfer files using the FTAM standard. Microcomputers are somewhat exempt because GOSIP is only required for host systems, which are mostly minicomputers and mainframes. However, any microcomputer linked to a host can remotely read OSI-compliant E-mail or download files. The organization that decides which protocols to add to the GOSIP specification is the inter-agency GOSIP Advanced Requirements Group in Gaithersburg, Maryland. BThe General Purpose Interface Bus is a communications standard for sending data from the computer to a peripheral device such as a plotter or instrumentation unit. The GPIB was originally designed by Hewlett-Packard and is still called the HPIB or Hewlett-Packard Interface Bus. Because of conflicting standards from various instrument manufacturers, the GPIB has always been difficult from a programming standpoint. The Institute of Electrical and Electronics Engineers has now codified the GPIB as the IEEE Standard 488.2. ˆGenerally speaking, microcomputers send data to the video display screen in one of two modes, either text (character) mode or graphics mode. In text mode, the only characters that can be displayed on the screen are the ASCII characters. In graphics mode, lines and characters are drawn pixel by pixel so that programs have unlimited flexibility in creating images on the screen. Character attributes such as boldface and italics can be displayed so that they appear on the screen as they do in print. As more and more applications are written to take advantage of the graphics mode, the text mode will become a thing of the past. NThe term grep originated in the UNIX Operating System as a search command for locating text within data files. It is derived from the line editor command "g/re/p", which prints all lines containing a specified regular expression. The text to be located can be specific or can be a combination of certain characters and wildcard characters. The wildcard characters can represent any digit, letter, a designated number of characters, options, alternatives, or other specified groupings. As a verb, the term grep refers to the process of rapidly scanning a file or file set looking for a particular character string or pattern. Û>CSCW deals with the study and development of software systems that encourage organizational collaboration, called groupware. The purpose of groupware is to provide both structure and support to aid us in working together with our computers as tools. One definition for it might be "software for the group". Groupware is not just multi-user systems such as word processing or database systems on a network where multiple users can share the same files. Word processing systems become groupware when they interact with the various co-authors working simultaneously by identifying edits by the user making them, or if they interact with the users according to their roles: principal author, co-author, or editor. M@Typically a GUI allows several programs to be displayed in separate windows on the screen. The operator can move these windows around, change their sizes, and easily switch from one program to another. The programs have a consistent user interface that makes use of pull-down menus, dialogue boxes, and graphical objects such as icons, scroll bars, and buttons. Since all screen output is in graphics mode, text can be displayed in different fonts and sizes, and can be easily integrated with graphical data. In addition to a keyboard, GUIs commonly support the use of a mouse. Many of the concepts of the Graphical User Interface were originally developed at Xerox's Palo Alto Research Center (PARC) and first successfully brought to microcomputers with the Apple Macintosh. Presentation Manager is a GUI for IBM's OS/2. ]The dictionary defines hacker as a slang term describing a person who carries out or manages something successfully. It seems that the term hacker, as applied to a computer user, first came into use about the same time as microcomputers. A hacker is someone who spends many hours with the computer often successfully operating it by trial and error without first referring to the manual. A hacker is often a technical person in the computer field, such as an assembly language programmer or systems programmer. Today, the term hacker has taken on a negative meaning. The news media has often used the term hacker in a derogatory manner to refer to people that use their technical knowledge to gain unauthorized access into private computer systems and data banks. õWhen the first personal computers were introduced, the internal disk drives were over three inches in height such that only one could be fitted in each drive bay of the conventional desktop case. Today, those original floppy disk drives and hard disk drives are referred to as full-height drives. The later model drives including magnetic tape drives and optical disk drives are designed so that two and sometimes three devices can be mounted on top of each other in a single bay. A half-height drive measures only 1 5/8" high by 5 3/4" wide. With the cases designed to stand upright on the floor, as many as five or six half-height devices can be mounted one on top of the other. These computer cabinets are often called tower cases. 7\A hand scanner is a hand-held device that allows the operator to capture data into a application program. There are two kinds of hand scanners, one for scanning text and numbers and another for scanning graphics. Hand scanners for reading data can be positioned and enabled to input data as if it were coming from the keyboard. But, at this point in time, they cannot read documents or printed information that has been proportionally spaced, like books, magazines, and newspapers. They can mostly read text and numbers from computer print-outs. The graphics hand scanners are used to scan drawings, photos, logos, and clip art. Actually they create a file of whatever is scanned, in some graphics format for conversion and input to a desktop publishing, word processing, or CAD application program. ËA hard disk is a disk made of a rigid base, such as ceramic or aluminum, coated with a magnetic material and having a storage capacity measured in terms of megabytes. The rigid rotating platter of a hard disk allows for precise data recording, high density, and large storage capacities. Personal computer systems for home use often will have a hard disk with a storage capacity of 20-megabytes, 40-meg, or more. The sort of hard disks installed on personal computers today use a collection of methods called Winchester technology, so they are often referred to as Winchester disks. There are also cartridge hard disks that can be plugged in and removed nearly as easily as a floppy diskette. °>ST506/412 - A serial hard disk interface standard developed by Seagate Technology and used for most XT and AT hard disks. Maximum data transfer rate is 5 megabits/sec. IDE - (Integrated Drive Electronics) An IDE hard disk has the controller functions on the drive itself and instead of connecting to a controller, it attaches directly to the motherboard. Data transfer rate is about 7.5 megabits/sec. ESDI - (Enhanced Small Disk Interface) a standard developed by a consortium of 22 disk drive manufacturers. The ESDI provides for a maximum data transfer rate to and from a hard disk of 10 megabits/sec. SCSI - (Small Computer System Interface) a standard developed by Shugart Associates and approved by ANSI. The parallel SCSI uses a 50-pin connector and permits multiple devices to be daisy chained. Data transfer rate: Up to 32 megabits/sec. ˆPartitioning divides a single physical hard disk into multiple logical partitions. Hard disks are divided into partitions in a circular fashion. For example, a drive's first partition might extend from cylinder zero through 299, with the second partition beginning on cylinder 300 and extending through 599. This circular partitioning is most efficient since it minimizes the disk head travel when accessing data within a single partition. The partitions on a drive, even if there's only one, are managed by a special sector called the partition table, which is located at the very beginning of every hard disk. It defines the starting and ending locations for each partition. Each partition on a hard disk is blind to the existence of any others. By universal agreement, the operation of software inside a partition is completely contained within the bounds of that partition. !yIntroduced in 1985, a hardcard is a printed circuit board that contains a hard disk and the control electronics. It plugs into an expansion slot in the IBM-compatible microcomputers. Hardcards are noted for their high reliability and low power consumption partially due to the use of a voice coil actuator type of motor rather than a stepper motor. 10, 20, 40, 80, and 105-megabyte hardcards are available for non-volatile data storage with high-reliability. The newer high-capacity hardcards have access times less than 10 ms. 0The physical equipment and components in a computer system are referred to as the hardware. Examples of microcomputer hardware: printer modem keyboard math coprocessor display screen hard disk scanner floppy disk plotter power supply tape drive memory chips 9[The originator of the de facto standard for modems in the world of microcomputers was Hayes Microcomputer Products, Inc. In 1981, the company produced the first modem to operate with a command set. The set of commands that is used to control the operation of a modem is called the standard Hayes AT Command Set. Most of the commands are prefaced with an AT which stands for ATtention. Today, the term Hayes-compatible is used as an adjective to describe modems from other manufacturers that operate with the same command set as the popular Hayes modems. }When the read/write heads of a disk drive come into contact with the magnetic surface of a disk platter, you have a head crash. A head crash is one of the most dreaded types of system failures because it not only causes lost data but also damaged hardware. A head crash is usually caused by some sort of disk contamination or when the equipment is accidentally jolted. œ_The term heap is often used by programmers to refer to the portion of memory that is available after an application has been loaded. The size of this chunk of memory may change as a program executes. It is the responsibility of the operating system to keep track of the location and size of all the free chunks of memory within the heap and whether or not they are busy. Although DOS's memory management is adequate for most needs, it is afflicted with one problem: fragmentation. This happens when a number of memory blocks have been allocated and freed in a random fashion. This poor memory management could easily get you into a heap of trouble. ¤ The technology that has vastly increased the capacity of compact tape drives is called helical-scan recording. Originally invented for use in broadcast systems, helical-scan recording has been used in data storage systems since the mid 1970's. Both longitudinal and helical-scan recording technologies rely on magnetism to record data on back-up tapes. The basic differences between the two are the pattern in which data is recorded and the positioning of the heads used to read, write, and erase the data. Conventional longitudinal recording records a track of data straight across the width of a single-track tape, limited in size to the width of the tape (quarter inch). Helical-scan recording packs more data on the tape by positioning the tape at a 5-degree angle to the recording heads. Each data track is a 3 inch long diagonal. The magnetic tape used in helical-scan recording is of high quality. ‰}The hexadecimal numbering system has 16 as its base, as contrasted with the decimal system that has a base of 10. Hexadecimal refers to whole numbers in positional notation with 16 as the base. The first ten digits are represented by 0 through 9, and the last six digits represented by A, B, C, D, E, and F. Computer memory addresses are conveniently expressed in hexadecimal notation since the word length is a multiple of four. Four bits can be expressed with one hexadecimal digit. For example, 1011001010000111 binary is B287 in hexadecimal notation. A hexadecimal number is the 1-byte equivalent of an EBCDIC character. 7pThe Hercules Graphics Card is a video display adapter that provides both graphics and text at a resolution of 720x348 pixels. It was first introduced by Hercules Computer Technology in 1982 to fill a need for clear text and graphics on a monochrome display, not then available. It quickly became an industry standard. Many graphic software packages are capable of operating in a mode compatible with the "Herc card". In 1987, Hercules introduced the InColor Card that provides for 16 colors out of a palette of 64 and uses an EGA-compatible monitor. U]A high density diskette is one which has been manufactured with a special magnetic coating that allows a track to contain 15 sectors rather than the 8 or 9 on the standard diskettes. In the world of microcomputers, there are presently two physical sizes of diskettes, the 5.25" and the later model 3.5". With the 5.25" diskettes, the 1.2 MB floppies are high density. With the 3.5" diskettes, the 1.44 MB floppies are high density. These diskettes are often labeled as double-sided, high density, or DS/HD. See the table "Floppy Disk Specifications" for an overview. « The High Sierra specification is an industry-wide format specification for CD-ROM data. It defines the logical structure, the file structure and the record structures of a CD-ROM disk. It has also served as the basis for the ISO 9660, an international format standard for CD-ROM. The name High Sierra was taken from the place where the original CD-ROM meeting was held in November of 1985, near Lake Tahoe, Nevada. BlA high-level language is a programming language that is not dependent upon the machine language of a computer, requires a compiler to translate it into machine code, and has been designed to allow the use of words similar to those in the English language. COBOL and FORTRAN are examples of high-level languages. O^A home computer is a type of microcomputer for use in the home. It is a personal computer, moderately priced and intended for such activities as home management, education, record keeping, programming, telecommunications, and entertainment. There is a wide variety of software available designed for home use to help manage and organize the household, such as checkbook balancing, stock portfolio accounting, cookbook recipes, personal calendars, and others. The number of home entertainment and educational programs continues to increase and improve at an alarming rate. ‡TThe High Performance File System is a method of keeping track of the location of files in directories. It was introduced with version 1.2 of the OS/2 operating system by Microsoft. It is an improvement over File Allocation Table system used with DOS. The HPFS supports long, mixed-case filenames. That is, unlike the FAT, it does not restrict file naming to eight characters with a three character extension. The HPFS also exploits sophisticated data structures and several levels of caching to improve performance, and allows free-form information known as Extended Attributes (EAS) to be associated with files and directories. KThe term "hypertext" was coined in the mid-1960's by computer scientist Ted Nelson. The original idea of hypertexting came from Vannevar Bush, President Roosevelt's wartime science advisor. He proposed a machine called the "Memex" in an Atlantic Monthly magazine article in July, 1945 titled "As We May Think". The strict theoretical vision of hypertext proposes that every piece of text, every word, be treated as a linkable element of an information system. Huge amounts of data can be accessed and linked with a few key words or data associations. Hypertext software today supports not only links between text, but also between graphical, video, audio, and most importantly, executable program files in a hypertext environment to provide a robust multi-media database. GBoth the hardware and software for microcomputers can be described as being IBM-compatible. It is a general term sometimes interchanged with DOS-compatible. When referring to a computer, DOS compatibility means software that will run on an IBM PC and will run properly. When discussing a plug-in board, such as a memory expansion board, IBM-compatible means the board will work in microcomputer designed and built by IBM. However, devices and software may be IBM-compatible but not always compatible with each other. sZAn icon is an image, a figure, or a representation of an object or a process. With programs that operate in a graphics mode, icons appear on the screen as small symbols that can simplify access to another program, or a certain command, or data file. Icons act as pointers. For example, a wastebasket icon may represent the command to delete a file. The process is activated by moving the cursor onto the icon and pressing a mouse button or a certain key on the keyboard. The use of icons and a mouse as a type of graphical interface between man and machine is referred to as an object-oriented interface. <zIDE is a hard disk drive standard interface for microcomputers. It appeared in 1989 as a low-cost answer to two other standard hard disk interfaces, ESDI and SCSI. The distinguishing feature of the IDE interface is that it incorporates the drive controller functions right on the drive. Instead of connecting to a controller card, an IDE drive attaches directly to the motherboard. IDE drives offer a data transfer rate similar to the RLL ST506 type of drives, or about 7.5 megabits per second. See the Table "Disk Data Transfer Rates" for an overview. U=The IEEE 802 standards are a set of standards developed by the Institute of Electrical and Electronics Engineers to define methods of access and control on Local Area Networks. They correspond to the physical and data link layers of the ISO Open System Interconnection model, but divide the data-link layer into two sublayers, the LLC and the MAC layers. Three primary IEEE 802 Standards are in wide use: 802.3 covers bus networks that use Carrier Sense Multiple Access with Collision Detection (CSMA/CD) including both baseband and broadband networks. The baseband version is based on the Ethernet network developed by Xerox Corporation. 802.4 covers bus networks that use token-passing to regulate network access and traffic control. 802.5 covers ring networks using token passing such as token-ring. ×An index serves as a pointer or indicator. Consider the index finger. An index file is a cross-reference of fields in a database file or a cross-reference of words in a textual file. It is similar to the index in a book. The index file provides direct access to the data requested in a query, and for large databases is more efficient than a sequencial search. In programming, an index is a number or a subscript used to modify an address, often through addition. A clustered index is a file in which the logical, indexed order of the key values is the same as the physical order in which the corresponding rows exist in the table. The preferred plural is indexes, rather than the Latin-derived indices. s|An infobase is a repository of electronic information containing folios, references, links, and groups stored in a single computer file. It is driven by an electronic infobase manager, a software engine. The information is referenced, retrieved, viewed, modified, printed, and generally accessed with a software program specifically designed for that purpose. ÊAn ink jet printer is simply a printing device that sprays one or more colors of ink onto the paper. An ink-filled print cartridge moves sideways in small steps as the paper scrolls through length- wise. Ink jet printers are not nearly as popular as dot matrix printers but ink jet technologies are maturing and producing output quality approaching that of a laser jet printer. See PC/Computing magazine, NOV '90, pg 254, The Ink Jet Printer. XProgramming languages have instruction sets, the complete listing of the instructions available to the programmer. An instruction is a discrete step or statement in a computer program that tells the computer to do something. It can also identify data if required. ƒ`An integrated circuit is a complete electronic circuit contained on a tiny chip of silicon. Integrated circuits may consist of only a few transistors, capacitors, diodes, or resistors, or thousands of them. They are generally classified according to the complexity of their circuitry, and the approximate number of circuits on the chip. SSI - Small Scale Integration, 2 to 10 circuits MSI - Medium Scale Integration, 10 to 100 circuits LSI - Large Scale Integration, 100 to 1000 circuits VLSI - Very Large Scale Integration, 1000 to 10,000 circuits ULSI - Ultra Large Scale Integration, over 10,000 circuits @5The term interactive, when referring to a computer program or system, indicates that the program asks questions of the user and then takes action based on the response. This PC-GLOSSARY is somewhat interactive in that the entries displayed on your screen are entirely dependent on your actions as the operator. ~1Interlacing is a technique used by some video displays in which the electron beam repaints the screen by alternately displaying all the odd lines and then all the even lines. Thus, interlacing updates any single line on the screen only 30 times per second, yet it provides a refresh rate equivalent to 60 cycles per second. Non-interlaced The electron beam of a non-interlaced monitor refreshes all the lines on the display sequentially from top to bottom. Each pixel on every line of the screen is repainted. Non-interlaced methods require twice as much signal information in the same time frame as interlaced methods. (The information stored on a floppy or hard disk is arranged in a series of concentric circular paths called tracks. A single track on a standard IBM-compatible disk contains approximately nine thousand bytes of data. But since data is usually accessed in much smaller chunks, each track is divided into smaller sections called sectors, 512 bytes long. Think of a pie which has been cut into seventeen identical, and numbered slices. After the information contained in sector one of the current track is read, the next sector, number 2, must be read. However, by the time sector 1 has been moved into the CPU, the beginning of sector two has already passed under the read/write head. There is a delay before the disk rotates around to deliver sector 2. This problem was resolved by spreading the sequentially numbered sectors out around the disk. Instead of placing sector 2 immediately after sector 1, sector 2 could be placed a few sectors later. This sector staggering is known as sector interleaving. {An interpreter is a translator program for a high-level language that translates and executes the program at the same time. The program statements which are interpreted remain in their original source language, the way the programmer wrote them. That is, the program does not need to be compiled before execution. Each program statement is translated into machine language and executed or processed one by one until the program is finished. Interpreted programs run slower than compiled programs and must always be run with the interpreter loaded in memory. BASIC and dBase are examples of interpretive languages. þA temporary halt or suspension during the execution of a task, during which control is transferred to the operating system, is called an interrupt. It can be caused by internal or external conditions such as a signal indicating that an input/output device has completed the transfer of data. A computer's CPU has built into it the ability to be interrupted, combined with a convenient way of putting the task that's been interrupted on hold while the interrupt is being processed. Modern computers such as personal computers, which are designed to use interrupts, are called, in the terminology of circuit designers, `interrupt driven'. An armed interrupt accepts and holds the interruption signal while a disarmed interrupt ignores the signal. ÃUInterrupt request lines are physical connections between external hardware devices and the interrupt controllers. When a device, such as a floppy controller or a printer needs the attention of the CPU, handshaking signals are sent back and forth until a task is completed. On the PC and XT IBM-compatible systems, there are eight IRQ lines numbered IRQ0 through IRQ7. On the AT and PS/2 systems, there are sixteen IRQ lines numbered IRQ0 through IRQ15. In a particular system, the goal is to configure expansion boards so that each board has its own IRQ line. If you have two serial ports on your system, you know that IRQ3 and IRQ4 are taken. See the table "Interrupt Request Lines" ;UISA is an abbreviation for Industry Standard Architecture. It is an unofficial designation for the bus design of the IBM PC, IBM PC-XT, and IBM PC-AT microcomputers and compatibles. This original bus design allows for various adapter cards (Printed Circuit Boards) to be plugged into expansion slots on the system board (motherboard). Originally introduced with an 8-bit data path on the IBM PCs and PC-XTs, the ISA bus was expanded in 1984 with the PC-AT computer and its 16-bit path. ISA typically refers to the expansion slots, 8-bit or 16-bit slots. KISAM is an acronym for Indexed Sequential Access Method. It is a procedure for storing and retrieving data from a disk file. When the programmer designs the format of the file, a set of indexes is created which describes where the records of the file are located on the disk. This provides a quick method of retrieving the data, and eliminates the need to read all the data from the beginning to locate the desired information. The indexes can be stored as part of the data file or in a separate index file. WJThe Integrated Services Digital Network is an international telecommunications standard that allows a communications channel to simultaneously carry digital data as well as voice and video. Microcomputers can communicate over ISDN at speeds up to 64 Kbps using existing telephone wires but without a modem. An adapter card similar to a network interface card is needed. The Primary Rate Interface (PRI) provides services similar to a T-1 link while the Basic Rate Interface (BRI) line to your home or office provides three digital circuits. Two of those circuits provide the 64 Kbps lines for voice and data, the third to control the ISDN circuit. Today, ISDN only exists in a few cities but will spread quickly because it is of particular interest to the banking and financial services, as well as computer and communication firms. ]The International Standards Organization, based in Paris, develops standards for international and national data communications. The U.S. representative to the ISO is the American National Standards Institute, or ANSI. In the early 1970's, the ISO developed a standard model of a data communications system and called it the Open System Interconnection model. Consisting of seven layers, it describes what happens when a terminal talks to a computer or one computer talks to another. This model was designed to facilitate creating a system in which equipment from different vendors can communicate. The other data communication models are IBM's System Network Architecture (SNA) and Digital Equipment's DEC Network Architecture (DNA), which both pre-dated the OSI model. For more info on OSI, call Omnicom in Virginia, (703) 281-1135 zIn relational databases, a join refers to the combination of data selected according to specific criteria from several databases to form a new database. Two complete tables (databases) may be joined, or only selected fields from each. There are different types of joining operations. An equijoin is a join in which the new table contains two identical columns. If one of them is removed, the result is a natural join. An outer join includes all non-matching rows from one of the join tables in the result table. In a self join, column values in the same table are compared with one another. The different instances of the same table involved in the self join have to be aliased to distinguish them, and the column references have to be qualified with the appropriate aliases. N`A joystick is a two-dimensional potentiometer, an electromechanical input device with a vertical lever, pivoted so that it may be manipulated within 360 degrees. When connected to a computer, it can provide positional information for the movement of the cursor on a video display screen. The application program that is designed to receive input from a joystick, responds by moving a cursor or an image on the screen in the same direction as the movement of the joystick lever. Joysticks are connected to a computer with a cable and are primarily used to play video games. Often on Printed Circuit Boards the designer will allow the board to be set-up in a variety of ways depending on the particular needs of the user. This is accomplished by placing a pair of jumper pins in the circuit. If a small plastic-covered metal clip is placed over the open pair of pins, the circuit becomes closed. The small plastic-covered metal clips are actually electrical conductors and are properly called shunts but are often referred to as jumpers. Jumpers are also called Berg post jumpers or shorting posts. 3To right justify information is to place data or text in the rightmost position of a field or document so that the characters are aligned to a rightmost column position when read or printed. A word processing document that has been printed or displayed so that the characters are evenly aligned along the right side border is said to be right justified. The common practice of printing information whether it be a letter, a document, or a book, is to align the characters on the left border, left justified. 'sKermit is a protocol designed for transferring files between micro- computers and mainframe computers. It was developed by Frank DaCruz and Bill Catchings at Columbia University in New York and is widely accepted, especially in the academic world. Kermit was named after the fuzzy, green talking frog of Jim Henson's "The Muppet Show". There are both public domain, and copyrighted Kermit programs that not only include the protocol but are complete programs in themselves offering the communication functions needed for the particular machine on which they are running. Write for the complete Kermit protocol manual (more than 100 pgs.): Kermit Distribution, (212) 854-3703 Columbia University Center for Computing Activities 612 West 115 Street, New York, NY 10025 +A keyboard is an input device used like a typewriter to input data to a computer system. Keyboards have keys or buttons labeled with alphabetic, numeric, and special characters, such that when a key is depressed, the corresponding character code is transmitted to the computer program waiting to receive it. An Enhanced Keyboard is one that contains the ten or twelve function keys across the top and a keypad on the right. Keypad A keypad is an input device with buttons like a typewriter but a keypad only consists of the numbers and some special function keys, no alphabet keys. When the operator actuates one of the buttons, a corresponding code is transmitted to the computer. Keypads can be found as separate input devices or, most often, added to right side of enhanced keyboards. 2)One kilobyte is 1024 bytes (2 to the 10th power). 'Kilo' is a binary analog to the decimal unit 'thousand'. The size of memory in a microcomputer is measured in kilobytes, for example, 256K, 512K, 640K. Of course, 1024K equals 1 Megabyte. See the Conversion Table "Bytes to Terabytes" °9A kludge is a quick fix for a problem or an improvised change in a situation to overcome a design deficiency. A kludge is a remedy that works fine but must be pampered. ³_Laddr is a standard architecture for peripheral manufacturers developed jointly in June of 1990 by Microsoft, Compaq, Adaptec, NCR, and Western Digital. It is intended to provide consistency among vendors and developers of SCSI device drivers for OS/2. Microsoft is making Laddr a public domain product with no licensing fees. Laddr will allow developers to write compatible drivers and save considerable development time. OhWhen two or more computers are linked together for the purpose of sharing information and/or peripheral devices, a network is created. When the network is confined to a geographically restricted area, such as within the same building or perhaps on a college campus, it is referred to as a Local Area Network. There are three types of data transmission media used on most of today's LANs: a twisted-pair of wires, coaxial cable, and the newest, fiber optical cable. There are also three basic types of LAN topologies in use today: the ring, the star, and the bus or line. /A laptop computer is a type of microcomputer that is designed to be a self-contained unit, lightweight, and easily portable. Laptop computers are often battery powered with re-chargeable batteries. They can also be operated from an external power source. All laptops have the keyboard and some type of video display built-in. They also are equipped with diskette drives and often offer hard drives as an option. Laptop computers were popularized by Radio Shack's Model 100, which was introduced in 1984. –rThe laser printer is a peripheral device for the output of data from the computer, one page at a time rather than a character or a line at a time. The printed page is near typeset quality. The laser printer is a combination of an electrostatic copying machine and a computer printer. The output data from the computer is converted by an interface into a raster feed, similar to the impulses which a TV picture tube receives. The impulses cause the laser beam to scan a small drum which carries a positive electrical charge. Where the laser hits, the drum is discharged. A toner, which also carries a positive charge, is then applied to the drum. This toner, which is fine black powder, sticks only to the areas of the drum which have been discharged. As it rotates, the drum deposits the toner onto a negatively charged sheet of paper. Another roller then heats and bonds the toner to the page. ÒJA Local Area Wireless Network, as the name suggests, consists of a group of computers linked together by radio waves or infrared light rather than with some form of cabling. Wireless technologies fall into three categories: spread spectrum, narrow band, and infrared. The concept is new and is also referred to as Wireless LAN Technology or WIN for Wireless In-building Networks. Because of the wide range of frequencies available, wireless networks should be able to operate in close proximity to one another. Initially, the data transmission speed of wireless networks is about the same as Ethernet (10 mbps) but as the technology matures, speeds are expected to reach up to 100 megabits per second. ˆXAn abbreviation for Liquid Crystal Display, an LCD is a display using liquid crystal sealed between two pieces of glass and polarizers then activated by an external light source to form the various characters, as on a digital watch or portable computer. Some LCD monitors depend on the reflection of ambient light to present an image on the screen; others increase readability by supertwisting and backlighting the screen. The most promising type of LCD is the recently developed active- matrix or thin-film transistor (TFT) LCD. Within a few years, we should see 9 and 11 inch advanced-matrix LCD monitors, monochrome and color. ÔAn abbreviation for Light Emitting Diode, an LED is a semiconductor diode that emits light when a current is passed through it and is used for alphanumeric displays on electronic devices such as calculators. N4Printed output from a computer that appears to have been typewritten is referred to as letter quality. All daisy wheel printers and most ink jet printers produce letter quality output. Dot matrix printers that use a 24-pin print head provide near letter quality (NLQ) output, but the characters are not as dark and crisp. _[A light pen is a hand-held electrical device with a light sensitive probe or stylus, connected to the computer's graphics adapter board by a cable to send electron beams to the adapter. They are used for writing or sketching on the screen of a video display and provide input to an application program. A light pen can be used by an operator as a pointing device tool for making menu selections presented on the video display screen. A light pen is sensitive to receiving light as opposed to a flashlight which shines light. Light pens are not widely supported by software applications. . A linker is an executive program that connects different program segments so that they may be combined to form one executable program. A linker program often can combine compiled object modules and assembled routines together, from different programming languages, to create a single program. ;Linpack is a benchmark test program written in FORTRAN and used to measure performance of a computer system in solving dense systems of equations. It consists of a high percentage of floating point arithmetic operations. As it executes, it solves one hundred equations with one hundred unknowns. Since most of the work is done in a single subroutine, the Linpack test is mostly a measure of localized FORTRAN system performance or the compiler's efficiency. Linpack tests are often executed both in single precision and double precision to show the performance of a math coprocessor chip. The results should not be taken as a general measure of system performance. Jack Dongarro, the author of the Linpack program acts as the single point of contact for source, updates, and results from the Linpack. +An acronym for list processing, Lisp is a high-level programming language primarily designed to process data consisting of lists. Lisp is especially well suited for text manipulation and analysis. It was developed and introduced in 1958 by John McCarthy of MIT. Today, along with PROLOG, it is one of the most popular AI languages. Common Lisp is a dialect or subset of Lisp that is intended to serve as a standard version designed to run on a wide range of computer systems. The U.S. Department of Defense has adopted Common Lisp as one of its three official computer languages. A Lisp machine is a computer designed specifically for artificial intelligence applications and especially designed to run Lisp. Reference: Lisp by Doris Appleby, Byte magazine, NOV 1991, pg 165. •@The Livermore Loops benchmark test is a measure of floating point performance. It is a FORTRAN program that contains a broad sample of generic computations. There are 24 kernels, each tuned to test a different performance range of the FORTRAN development system being measured, such as, inner products, banded linear equations, tri-diagonal elimination, general linear recurrence, and Monte Carlo searches. The program is maintained by the Lawrence Livermore National Laboratory (LLNL) and is also available in the C language. Results of the Livermore Loops test are often given in millions of floating point operations per second, MFLOPS. GiThere are two ways to view the disk drives in your microcomputer system, either logically or physically. When you view a drive physically, you are looking at how many tangible drives your system can access. For example, if you have two hard disk drives in your system, the first will be physical drive 1 and the second will be drive 2. These drive numbers are the same as those referenced by FDISK. These physical drives may be logically subdivided to produce logical drives during the disk partitioning process. Physical drives are referred to by number while logical drives are referred to by letter. You could have three logical drives with C and D residing on the physical drive 1 and drive E residing on physical drive 2. You could also have other logical drives such as RAM Disks or remote disks in a network. "Login, logon The terms login and/or logon are used to describe the process of identifying oneself to a multiuser computer system after making a connection to it over communication lines or network cables. The login procedure provides a means of identifying authorized users by name and an optional password. Logout, logoff The terms logout and/or logoff are used to describe the process of terminating a session with a multiuser computer system. Logging off or out is not the same as shutting down or turning off a computer. .[There is a DOS utility program called "CHKDSK" which performs an analysis of the integrity of the files on a hard disk. If all of the files and sub-directories are properly accounted for in the File Allocation Table (FAT), then CHKDSK provides information about the disk including its size, the number of files found, the amount of storage space remaining, and other useful data. If CHKDSK encounters a problem with one or more files, you may be presented with a message similar to this: "5 lost allocation units found in 3 chains. Convert lost chains to files (Y/N) ?" See your DOS Manual. This message indicates that portions of a file (or files) have become detached from the rest of the file or that a file has become separated from its directory entry. You have lost chains. )A programming language, using symbolic code, that is based on the machine language of a particular computer and requires an assembler to translate it into actual machine language, is referred to as a low-level language. A particular computer's assembly language is always considered as a low-level language. The C-Language is often referred to as a low-level language but it does not consist entirely of symbolic code. 'C' features economy of expression, modern control flow and data structures. úfThese are logical device names for parallel printers or ports. With DOS operating system, LPT1, LPT2, and LPT3 are reserved names for up to three parallel printer ports. LPT1 is usually the same as the primary DOS hard-copy output device PRN. pIComputer programs can be described as being machine dependent or as having a certain degree of machine independence. If the operation of a computer program relies on a particular machine architecture or operating system for successful operation, that program is said to be machine dependent. All assembly language programs are machine dependent. Most of the high-level languages, particularly the C-language, are relatively machine independent or portable. That is, a program written in the C-language under one operating system, such as DOS, can often be easily transferred to a UNIX system, for example. Þ2The programming language comprised of a set of unique machine codes that can be directly executed by a given computer is called its machine language. Machine language is the lowest level of programming. It is written in a series of bits used to communicate primitive instructions to the computer. Each type of computer has its own variety of machine language. Programmers rarely code in machine language because instructions and data must be in binary notation. ÕdA macro is a stored set of commands or instructions invoked by a single command or instruction. Macro implies substitution. One example is a keyboard macro. If you discover a sequence of keystrokes that are used over and over, a macro can be created which contains those keystrokes. It can then be invoked later, often with a single keystroke, to save time and possible errors. As another example, a spreadsheet macro is a set of instructions written into the worksheet that, upon execution, performs a series of spreadsheet operations in a previously specified order. The steps necessary to copy the values in one row to another row could be stored a macro, and then executed with a single keystroke. ®fMag tape is an abbreviation for the various kinds of magnetic recording tape used to store computer programs and data. The tapes are used to store information off-line as backups. Large computer systems and minicomputers use open reel magnetic tapes with 7 or 9 tracks or recording channels and densities of 200, 556, 800, 1600, or 6250 bits per inch (bpi). Microcomputers equipped with tape backup systems use magnetic tape contained in cartridges or cassettes of many sizes. The data that is stored and retrieved from mag tapes is done in a sequential fashion. That is, reading or writing a specific item on the tape requires reading everything in front of it. CA magneto-optical disc drive is a microcomputer peripheral device for storing and retrieving data. The drive is similar to a floppy disc drive; it can be mounted internally or reside in a external case. The discs or cartridges are removable and come in two sizes, 3.5" and 5.25". The 3.5" optical disc has a storage capacity of 128 megabytes with average access times in the 30 to 60 millisecond range. The 5.25" disc will store up to 650 megabytes on one double sided disc with average access times in the 60 to 100 millisecond range. Magneto-optical disc drives utilize SCSI controllers and have been in use since 1988. þ;The main memory of a computer is the storage area for programs, along with its data, while they are executing. Memory is also called RAM for Random Access Memory. The term 'random access' refers to the fact that any address in memory can be accessed at random, or in no particular order. The first computer memories were serial access memories, which meant that whole sequences of data had to read or accessed before arriving at the desired piece of information. Serial access memories are no longer in use. Data, temporarily stored in RAM, should not be confused with data stored 'permanently' on a mass storage unit. Data and programs stored in RAM are lost when the power is turned-off. RAM is volatile, mass storage units are non-volatile. P%Large computers are referred to as mainframes. More precisely, the mainframe is the piece of equipment on large computers that contains the CPU. Mainframe computers most commonly operate with word lengths of 32-bits or more, have large memory capacities, and are used where large volumes of data are stored and processed. The term 'mainframe' is really a holdover from the days when most computer systems occupied the space of several rooms. There really was a main frame, and several secondary frames or large rack and panel cabinets that held thousands of vacuum tubes. :DThe Maltron keyboard layout allows potentially faster typing speeds and is easier to learn than the traditional QWERTY layout. The keyboard is designed so that the keys used most frequently are positioned beneath the strongest fingers. Thus, the home keys for the right hand are THOR and for the left hand, ANIS. Up to eight keys are assigned to each thumb. Each key is positioned at the correct height for the finger that uses it, thus minimizing unnaturally long finger stretches and making the keyboard less tiring to use than the QWERTY keyboard. ˆpAs the name suggests, a Metropolitan Area Network is a network that spans a region such as a city. MANs are high-speed public networks (100 megabits/per second or more) capable of voice and data transmission over a range of 25 to 50 miles (about 40 to 80 kilometers). MANs often connect multiple Local Area Networks typically using fiber optics to transmit voice and data signals. «|A math coprocessor is a special purpose processor chip, that works together with a general purpose or main processor, but optimized for mathematical operations. While general purpose processors require software routines to execute floating point and large integer calculations, math coprocessors execute these functions in hardware, performing the calculations many times faster than is possible with software. In the world of microcomputers, a math coprocessor can boost the performance of math-intensive applications by a factor of from 10 to 100, just by adding a single chip on the motherboard. For the IBM-compatible microcomputers, Intel Corp. designed the 8087 math coprocessor chip to work with the 8086 and 8088 micro- processors and the NEC V20 and V30 processors. Intel also has math coprocessors for the 80286 and 80386-based machines. Math coprocessors, like microprocessors, come in a variety of speeds. RSMAU and MSAU are abbreviations for Multi-Station Access Unit. In a token ring network environment, the MAU is a multi-port hardware device into which up to 16 workstations are connected. The MAU provides centralized control of network connections. The MAU moves signals from one station to the next active station on the ring. It also provides a built-in relay to prevent a break in network service should a single connection or device fail. In addition to the ports for workstation connections, the MAU has two additional ports, the RI (Ring-In) and RO (Ring-Out) ports used to interconnect two or more MAUs. In a coax Ethernet network, the MAU uses only one wire for both transmitting and receiving. With 10Base-T Ethernet, the MAU must accommodate two wire pairs, one pair for transmitting and the other pair for receiving. |IBM's proprietary Micro Channel Architecture is the data bus of their PS/2 line of microcomputers. This is the data bus of the computer that controls the flow of data between processors and to and from such peripheral devices as the keyboard, monitor, and printer. The Micro Channel has three main aspects: a 32-bit bandwidth, the I/O processors, and the multimaster control, which acts like a data traffic cop to allow multiprocessors to work simultaneously. The multimaster part of the bus provides the biggest benefits of the Micro Channel. The biggest drawback to the MCA is the fact that it is not downward compatible with IBM's earlier microcomputer products. Boards that plug into the MCA bus are not interchangeable with the XT's and AT's. :The Monochrome Display Adapter is a single color video controller card for the IBM-compatible computers. It was introduced by IBM in the early 1980's to display text characters but not graphics. The MDA generates a screen resolution of 720x350 pixels with each character occupying a cell of 9x14 dots. {iOne megabyte is exactly 1,048,576 bytes (1024 times 1024), or (2 to the 20th power). 'Mega' is a binary analog to the decimal unit 'million'. The capacity of a hard disk drive for a personal computer is measured in megabytes, a 20-Meg drive, a 40-Meg drive. One 'Meg' of memory is the same as 1024 kilobytes. See the Conversion Table "Bytes to Terabytes" 'A memory chip is a very small piece of a semiconductor, usually silicon, on which microscopic electronic devices are formed for storing and retrieving data bits. The number of bits that can be stored in a single memory chip continues to grow and the speed at which the chips operate, continues to get faster and faster. Memory chips come in a variety of styles: DIP's, SIP's, and SIMM's. Some of the most common memory chips in use today are the 64K, 128K, and 256K chips operating at speeds of 150, 120, and 100 nanoseconds. 1 megabit chips are also available and by the early 1990's, 4 megabit chips are expected to go into full-scale production. By the mid-1990's, memory chips capable of storing 16 megabits of data with average access speeds of 80 nanoseconds are expected. /pMemory paging is the transfer of program segments into and out of memory in a virtual memory environment. With the 80386 microprocessor, a page is a 4K-byte piece of memory. Pages are placed at locations, called page frames, whose addresses are 4K bytes apart. A data item that starts at one of these 4K multiple addresses is said to be "aligned on a page boundary". Only the first twenty bits of a 32-bit page address are significant; the last twelve are always zero. When virtual memory is in use, pages are swapped between disk and RAM as needed. The 4K-byte sections on disk that hold pages are called page slots. Memory paging can only be used in the protected mode of the 80286 and 80386 CPUs, never in real mode. Nearly all 80386 operating systems will do at least some memory paging. 7+Programs are referred to as being memory resident when they remain in memory until explicitly removed or until the power is shut-off. Such programs are called TSR programs or pop-ups because they remain in memory even after program termination. TSR is an acronym for Terminate and Stay Resident. ê|With microcomputers operating under DOS, the amount of memory that can be utilized for working programs and data, without the use of extended or expanded memory, is 640 kilobytes. Extended and expanded memory are of practical benefit only if used with software specifically written to take advantage of them. All of Intel's microprocessor chips can utilize expanded memory but only the 80286, 80386 and 80486 chips can utilize extended memory. Think of extended memory as being similar to a hard drive, all of it is continuously available to the system. Expanded memory is like a removable drive, the system can access only the portion that is currently mounted and it requires a special agent to access other portions. ÷The performance of a computer system is often evaluated by measuring its operational speed in a variety of different tasks. The speed at which a system performs floating point operations is measured in units of Whetstones or floating point operations per second (flops). MFLOPS then is an acronym for Millions of FLoating point Operations Per Second. With these benchmark tests that measure performance in Dhrystones, Whetstones, or MFLOPS, higher numbers indicate faster performance. 1QA variety of techniques or schemes exist for writing or encoding data to a hard disk drive. One of the earliest and therefore the most popular techniques is MFM or Modified Frequency Modulation encoding. Its popularity has diminished since the introduction of RLL data encoding formats, which allow for more data to be packed onto the hard disk. As the name implies, MFM is an enhancement to an earlier recording method called Frequency Modulation. The modified FM technique reduces the number of synchronization bits recorded on the disk. t MHS is an abbreviation for the Message Handling System which is the OSI E-mail standard also known as the X.400 specification. The purpose of this global standard is to provide a guideline for developers of electronic mail systems. The goal is to be able to easily send electronic information from/to any computer system in the world with minimal conversion. NkMHz is an abbreviation for megahertz. It is a unit of measurement. One Hertz (Hz) is equal to one cycle per second. Heinrich R. Hertz, a German physicist, first detected electromagnetic waves in 1883. Megahertz is a unit of measurement for indicating the frequency of one million electrical vibration cycles per second. The original IBM-Personal Computers in the early 1980's were controlled by Central Processing Units (CPUs) that were synchronized with clock crystals vibrating at 4.77 megahertz. The bandwidth of your computer monitor is also measured in MHz. ½DA mickey is a unit of measurement typically set at 1/200th of an inch. It is commonly used to designate the shortest distance that a mouse cursor can travel on the video display tube. ò#In general, as a class of computers, the microcomputer is the smallest and least expensive. They are fully operational and use microprocessors as their central processing unit. Microcomputers are used in the home as personal computers; they are also widely used in businesses and schools. All of the following types of microcomputers are defined in more detail in this glossary. Laptop computer Desktop computer Home computer Personal computer Portable computer ç9A microprocessor is the central processing unit (CPU) of a computer, a computer chip acting as the brains of the computer. IBM, Compaq, and many other `IBM-compatible' personal computers get their thinking power or instruction set from Intel's chips. Examples are Intel's 8086 family of microprocessor chips: ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ ³ 8086 ³ 80286 ³ 80386 ³ ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´ ³ Information Handling ³ 16 bits ³ 32 bits ³ 32 bits ³ ³ Hardware Communication ³ 8 bits ³ 16 bits ³ 32 bits ³ ³ Clock Speed (in MHz) ³ 4.77 & 8 ³ 8 to 16 ³ 12 to 33 ³ ³ RAM Addressability ³ 1 MByte ³ 16 MByte ³ 4 GByte ³ ³ IBM System Usage ³ PC & XT ³ PC/AT ³ PS/2,70,80 ³ ³ Compaq Systems ³ Compaq ³ Compaq-286 ³ Compaq-386 ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ £MIDI, an acronym for Musical Instrument Digital Interface. An interface card or adapter board for connecting a musical instrument to a microcomputer is called a MIDI Adapter. Multiple musical instrument keyboards can be daisy-chained together and played simultaneously with the help of the computer and related software. The various operations of the musical keyboard can be captured, saved, edited, and played back to one or more musical instruments. Each instrument, of course, must be MIDI compatible. Your music can be digitally recorded, then have previous tracks played back as you record new tracks, creating the sound of an entire orchestra. ñcA computer that is usually more powerful than a microcomputer, and usually less powerful than a mainframe computer is called a minicomputer. Minicomputers are most often found in large businesses and very rarely found in the home. As computers become more and more powerful each year, the exact definitions of micro's, mini's, and mainframe computers continue to change. In 1959, Digital Equipment Corp. launched the minicomputer industry with the introduction of the PDP-1. cAn acronym for Million Instructions Per Second, MIPS refers to the average number of machine language instructions a computer can perform or execute in one second. However, it can be shown that the same computer can execute two different loops of code to estimate MIPS, and their execution times will differ significantly. MIPS should therefore be used only as a very general measure of performance between different types of computers. In order to obtain accurate performance data to compare similar computers, each subsystem must be isolated, and practically speaking, this is an almost impossible task. More realistic benchmark testing occurs at the application level. MIPS is sometimes jokingly referred to as Meaningless Indicator of Processor Speed. `A mnemonic is an abbreviated name for a computer instruction, such as JMP, ADD, CLR, STO, INIT. A mnemonic name for an instruction or an operation makes it easy to remember and convenient for the translator or programmer. Assembly language source code consists of many different mnemonics which are translated or assembled into machine code. PEssentially, MNP is a special error correction protocol for the transfer of data. The protocol is implemented not through software but as an integral part of the modem, ie. hardware. The Microcom Networking Protocol was developed by Microcom to serve as an industry standard for high-speed, error-free communications. Modems that have MNP capabilities support common standards including Bell 103, 212A, CCITT V.22, V.22 bis, and V.29. In other words, all modem speeds from 300 to 9600 baud. There are six different classes of MNP modems. One of the problems encountered using MNP modems at any of the 6 classes is determining the particular class of MNP at which it is operating. Also keep in mind that, for MNP to successfully work, both the sending modem and the modem you are connected to must have some form of MNP. 1The term modem is an acronym for MOdulator-DEModulator. It is a device that converts digital data from a computer or terminal into analog data that can be transmitted over telephone lines. On the receiving end, it then converts the analog data back to digital data. A modem handles the dialing and answering of a telephone call and generates the speed of the data transmission, which is measured in bits per second. Modem speeds: 300 1200 2400 9600 19200 and higher. The telephone industry sometimes refers to a modem as a dataset. —TA television set contains a monitor. The video screen of a cathode ray tube (CRT) is a monitor. There are monochrome and color monitors, for viewing the output of a computer program. A multi-mode monitor is a color monitor that automatically adjusts to graphics board scanning frequencies so that it is compatible with a variety of graphics adapters such as the CGA, MCGA, EGA, PGC, and VGA. ’KThese are four of the basic Metal-Oxide Semiconductor manufacturing technologies. MOS refers to the three layers used in forming the gate structure of a field-effect transistor (FET). MOS circuits offer low power dissipation and allow transistors to be jammed close together before a critical heat problem arises. PMOS is a silicon-gate P-channel MOS process that uses currents made up of positive charges. PMOS is the oldest type of MOS circuit. NMOS is a silicon-gate N-channel MOS process that uses currents made up of negative charges. NMOS is at least twice as fast as PMOS. CMOS, Complementary MOS, is virtually immune to noise, runs off almost any power supply, and is an extremely low-power circuit technique. For these reasons, CMOS technology found its way into microprocessors and with this advancement came the need for high- density CMOS-compatible memory chips, dynamic RAM. ë The main circuit board of a microcomputer is called the motherboard. The motherboard is a printed circuit board or system board which is an interconnecting assembly into which smaller printed circuit boards, or controller cards, or modules are plugged. The smaller cards are sometimes called daughter boards. Memory chips are often plugged directly into the motherboard or can reside on a memory expansion card which is then plugged into an expansion slot on the motherboard. ¡OA mouse is a small hand-held device which duplicates its movement on a tabletop to the cursor on your screen. A mouse essentially replaces the cursor controls (arrow) keys on the keyboard. Its purpose is to send signals that indicate to the computer the direction and velocity with which the mouse is being moved. A mouse has one or more buttons that simulate certain keys. There are basically four different types of computer mice: The mechanical mouse uses a rolling ball, which protrudes from the bottom to move two encoders ( for the X-axis and the Y-axis). The wheel mouse has two wheels, each connected to an encoder, which protrude from the bottom to rotate the encoders. The encoders in the opto-mechanical mouse have holes that permit light to be transmitted through them. The optical mouse has two LEDs that generate different wavelengths of light and associated phototransistors. bMPC, or Multimedia Personal Computing, refers to a technical standard set by the MPC Marketing Council, a group of hardware and software manufacturers led by Tandy and Microsoft corporations. The standard establishes a minimum configuration for running multimedia on MS-DOS microcomputers. An MPC is an IBM-compatible microcomputer with a CD-ROM drive, audio board, Microsoft Windows with multimedia extensions, and audio output. The minimum hardware configuration of an MPC is a 80286 CPU running at 10 Mhz with 2 megabytes of RAM, a 30 megabyte hard drive, and a VGA display. For more information, contact: Multimedia PC Marketing Council 1730 M Street NW, Suite 700 Washington, DC 20036 ñlMTBF is an acronym for Mean Time Between Failures. MTBF is a measure of the average amount of time, usually given in hours, that a hardware component continues to operate without failure. For most manufacturers, it is the number of failures that occur during the factory test period divided into the total number of hours under observation. It could also be derived from the results of various field testing. For example, the average life of a microcomputer hard disk drive is between 10,000 and 40,000 hours. That figure is based on "power on" hours. Keep in mind that a 40,000 MTBF number from one manufacturer could be significantly more or significantly less reliable than a 40,000 MTBF number from another manufacturer. nA video display monitor that is capable of automatically adjusting to the synchronization frequency of the video board that is sending signals to it is called a multi-synchronous monitor. The multi-sync monitor was popularized by the NEC MultiSync monitor. /VMultitasking is an operating system feature that allows several programs to appear to be operating at the same time. Actually a scheduling program periodically switches between the two or more programs, giving each a measured portion of time (time slice) to use the CPU. True multitasking is not available under DOS. Here are some examples of multitasking operating environments that can run DOS programs: DESQview by Quarterdeck Office Systems OS/2 by IBM Windows by Microsoft Corp. ("Named pipes" is a software facility within the network operating system that allows processes on separate machines to communicate with each other across a network. It provides a simple way for application developers to write sophisticated distributed network applications. zcOne billionth of a second is called a nanosecond, that's one thousand-millionth of a second. Sometimes a nanosecond is called a billisecond. The speed of logic and memory chips is measured in nanoseconds. The RAM chips in your computer are rated in nanoseconds according to their speed. They may be 150ns, 120ns, 100ns or 80 nanosecond chips. A fast microprocessor can carry out an instruction in less than one nanosecond. Electricity travels approximately one foot per nanosecond. The combining form 'nano' is derived from the Greek word nanos for dwarf and is used to designate ten to the minus ninth power.`NAPLPS is an abbreviation for North American Presentation-Level Protocol Syntax. It is a text and graphics data transmission format for sending large amounts of information between computers. NAPLPS was originally developed for videotext and teletext systems through the Canadian Standards Association. It was later enhanced by AT&T, and in 1983 became an ANSI standard. For the most part, NAPLPS has been replaced on CompuServe with a newer protocol called GIF, Graphics Interchange Format. Commercially, NAPLPS is still alive, as a number of videotext systems are based on NAPLPS. ÛTGenerally, native mode refers to an operational state of a computer that is executing a program in its native machine language. With microcomputers, the term native mode refers to the operational state of the computer whereby the full potential of the system is being utilized. For example, with the new 80386 microprocessor systems, when the resident operating system has full access to all RAM and properly utilizes the 32-bit data bus, it is said to be operating in native mode. Contrast with emulation mode or protected mode. Assembly language is sometimes referred to as native language. A native compiler is one that produces executable code for only a particular processor or brand of equipment. ŒThe NCGA is a professional organization founded in 1979 that helps to develop and promote the computer graphics industry and graphics applications in business, science, government, and the arts. To bring some standardization to the process of measuring a computer system's graphic capabilities, the NCGA formed a committee comprised of major hardware vendors. They have released a program called the Picture-Level Benchmark (PLB) to the public domain that provides three standardized components that can be applied to any graphical hardware platform. BIF - Benchmark Interface Format, a standardized file structure. BTM - Benchmark Timing Methodology, measures response times. BRF - Benchmark Report Format, defines a standard reporting format. For more information: NCGA, Standards and Technical Services Dept. 2722 Merrilee Drive #200, Fairfax, VA 22031 |dContrary to popular belief, although it often refers to a certain type of dedicated computer user, the term nerd did not originate anywhere in the field of computers. The dictionary describes a nerd as any person regarded as contemptibly dull, unsophisticated, or ineffective. A nerd was first described by Dr. Seuss back in 1950. In his book "If I Ran the Zoo", Seuss talks about young Gerald McGrew who wants to repopulate the city zoo with the "strangest odd creatures that ever did walk." Among them is the "Nerd," an unattractive creature with a mop of hair, flowing whiskers, and a surly expression. A computer nerd is similar to but not as remote as a computer geek. A geek is one who eats computer bugs for a living, or one who fulfills all of the dreariest negative stereotypes about hackers; an asocial, malodorous, pasty-faced monomaniac with zero personality. "An acronym for NetBIOS Extended User Interface, NetBEUI is a network device driver or transport driver supplied with the LAN Manager network operating system. It is the Application Program Interface (API) that allows a program running on a workstation access to the LAN facilities. The NetBEUI driver can bind with as many as eight media access control drivers. Many vendors either provide their version of NetBEUI to interface with their hardware or emulate its session-layer communications services in their network products. G@An acronym for Network Basic Input/Output System, NetBIOS is the software originally developed by IBM and Sytek to link a PC network operating system with specific hardware. It is the Application Program Interface (API) that lets an IBM PC program explicitly access the LAN facilities. NetBIOS can also open communications between workstations on a network at the session layer of the OSI model. Many vendors either provide their version of NetBIOS to interface with their hardware or emulate its session-layer communications services in their network products. BEWhen two or more computers are linked together for the purpose of sharing information and/or peripheral devices, a network is created. A network is also a database design technique for managing a collection of related programs for loading, accessing, and controlling the information that makes up the database. 0;Inside each file server and workstation on a network, a network interface card communicates with the network operating system through either the NetBIOS or special driver software. The size and on-board processing power of the network interface card varies greatly among vendors but most have added capabilities such as processing chips to minimize the burden on the host system. The network interface cards and the type of cabling for connecting the workstations to the file server go hand in hand. Cable choices include twisted-pair telephone wire, shielded twisted-pair data-grade wire, coaxial cable, and fiber-optic cable. Network interface cards are used with the following types of LANs: ARCnet, Ethernet, and Token-ring. AT&T refers to network interface cards as Network Access Units. åXA network operating system consists of a set of programs and related system files that coordinate the activities of providing services to the workstations and peripheral devices attached to a local area network. These programs reside and execute on the file server and handle the requests for data from all the workstations on the network. The network operating system also performs the task of controlling access to the network, often with a user identification and password scheme. It also manages the details of resource allocation and sharing, data protection, and error control. The three most popular network operating systems in use today are: NetWare from Novell, LAN Manager from Microsoft, and Banyan's Vines. ébNeural networking, or synthetic neurology, is the promising new computer field dealing with the task of using computers to simulate the processing power of the complex human brain. Although this task is extremely complex, the first traditional problems to be addressed will involve pattern and speech recognition, object classification, machine learning, dynamic adaptation, and a host of other real-world needs. In the near future, it will be possible to design and train synthetic neural networks to perform operations to convert written text to speech, understand continuous unbroken speech, read poorly written handwriting, win complex board games, and other tasks that require a high degree of associative recognition. ¦DThe IBM Dictionary of Computing defines nibble as a deprecated term for a part of a byte, usually a halfbyte. We're not sure what they mean by "deprecated". A nibble is half a byte or four bits. A nibble is most often used to represent a hexadecimal digit; however when representing a BCD value the hexadecimal values A through F (1010-1111 binary) are not used. Nybble is an alternate spelling for nibble. ý0The term NiCad is an abbreviation for nickel-cadmium. NiCad batteries are used to provide power for today's high-tech laptop and notebook microcomputers. They are rechargeable and provide a relatively constant voltage which is an advantage for voltage-sensitive computer components. Recharged NiCad batteries are most efficient when recharged only after they have been fully discharged. One that has been only partially drained and then recharged will not deliver its full rated capacity. ‹XWhen any number of computers are connected together in a network, each of the workstations or terminals are referred to as nodes, and are assigned unique addresses within that network. A node is also an electrical connection point on a printed circuit board or component. With database management systems, a node is a data item that can be retrieved by two or more routes. TA notebook PC is a portable personal computer with the following general characteristics. û Battery operated, re-chargeable û Weight: less than about 9 pounds û Size: about 2 inches thick, 9 inches high, and 12 inches wide. û Hard disk: 20 megabytes or more, mostly the 2.5 inch size. û CPU speed: At least 16 Mhz ¨:NSTL, National Software Testing Laboratories Founded in 1983, the NSTL was a pioneer in the objective and comparative testing of microcomputer hardware and software. Today, the NSTL is recognized as a leading independent research organization exclusively devoted to the scientific testing of microcomputer technology. The international headquarters in suburban Philadelphia include a 20,000 square foot test facility that incorporates advanced and versatile testing equipment. The NSTL is completely independent and impartial while adhering to a firm policy of accepting no advertising. The test reports print exactly what the tests reveal, good and bad. The National Television Standards Committee governs the standard for television and video playback and recording in the United States. The group was organized in 1941 when TV broadcasting first began on a wide scale. Twenty years later higher standards were adopted in Europe with the PAL and SECAM systems, both incompatible with the NTSC standard of North America. The NTSC standard (specification RS-170A) provides for 525 scan lines of resolution and is transmitted at 60 half frames per second. It is an interlaced signal which means that it scans every other line each time the screen is refreshed. The signal is generated as a composite of red, green, and blue signals for color. It also includes an FM frequency for audio and a signal for stereo. *The term null is used to mean empty, nothing, no information, no data, or an empty field. The ASCII character code for null is NUL and is represented by the decimal number zero, but is not the same as the number zero. It is a non-printing character. In a Database Management System, a null field is an empty field, in contrast to a field containing zero. Null means lack of information, whereas zero is a number. Null fields indicate that information such as age, year of birth, or price is not available or not reported. The value of zero in these cases would be erroneous and could make some statistics and comparisons unrealistic. Q0The RS-232 standard defines two types of interfaces, data terminal equipment (DTE), and data communication equipment (DCE). Personal computers are almost always configured as DTE devices while a device like a modem or mouse is typically configured as a DCE device. When connecting two like devices, DTE to DTE or DCE to DCE, you must use a null modem cable or modem-eliminator adapter. The following list shows the pin to pin connections required to make a null modem cable between DB-25S and DB-25P connectors: 1-1, 2-3, 3-2, 4-5, 5-4, 6-20, 7-7, 20-6 Ê}An information processing technology that converts human readable data into another medium for computer input is called Optical Character Recognition. An OCR peripheral device accepts a printed document as input, to identify the characters by their shape from the light that is reflected and creates an output disk file. For best results, the printed page must contain only characters of a type that are easily read by the OCR device and located on the page within certain margins. When choosing an OCR product, the prime consideration should be the program's level of accuracy as it applies to the type of document to be scanned. Accuracy levels less than 97% are often considered poor. Generally, any manufacturer that sells his product to a reseller is referred to as an OEM. However, the term is also used to refer to the reseller. In fact, OEM and VAR, Value Added Reseller, are used interchangeably. They are relative terms. With complex products such as computer systems, there are OEM's and VAR's throughout the manufacturing process. No one company manufactures all the components of a computer system, not even the large computer corporations such as Compaq, IBM, or Tandy. š6Pronounced oh-lay, OLE is a software technology, an inter-process communication within the Windows operating environment. It allows the operator to embed one object within another, even though the different types of objects may have been created using different programs. OLE differs from traditional export/import methods. If the embedded object is updated by the originating program, the changes are also reflected in the embedding program. For example, a graph from a spreadsheet can be embedded in a word processing document. If the numbers in the spreadsheet are changed, the updates are reflected in the graph in the word processing document. ËmThe term on-line is used to describe equipment, peripheral devices, and persons who are in direct communication with the central processing unit of a computer system. For example, a printer is described as being on-line if it is attached, turned-on, and the on-line indicator is lit. The printer can be taken off-line to advance the paper and still be attached with power applied. An on-line database refers to a file of information that can be directly accessed by the operator. Off-line has just the opposite meaning. Off-line storage refers to data that has been removed from the system and stored in a place of safe-keeping such as a library. Magnetic backup tapes are stored off-line. Ø]The term on-line services refers to the network information services provided by large computer systems to the owners of personal computers with modems. The types of services offered vary by company but may include access to libraries of programs and data, electronic mail, on-line shopping malls, forums, hardware and software vendor support, financial data, stock market quotes, and research capabilities. Further information on the following on-line services can be found under their separate entries in the PC-GLOSSARY. BIX, BYTE Information Exchange, DJNR, Dow-Jones News/Retrieval CIS, CompuServe Information Services GEnie, Prodigy, and America Online @Object-oriented programming is a technology for creating programs that are made up of self-sufficient modules that contain all of the information needed to manipulate a given data structure. The modules are created in class hierarchies so that the code or methods of a class can be passed to other modules. New object modules can be easily created by inheriting the characteristics of existing classes. The first object-oriented programming language was Smalltalk from Xerox's Palo Alto Research Center in California. BThe operating system is the master control program that interacts with other system and application programs within a computer. The central core or kernel of the operating system must reside in memory at all times. Computer programs are written to run under a particular operating system, such as DOS, or OS/2, or UNIX. Operating systems are also called the executive or supervisor. Î Orphan and widow are word processing terms used to describe two undesirable formatting conditions of a printed page. The last line of a paragraph sitting alone at the top of a page of text is called an orphan. When the first line of a paragraph sits alone at the bottom of a page of text, it is called a widow. The best word processing programs have built-in features to prevent orphan and widow lines from appearing on the printed document. ÈDeveloped through a joint effort by IBM and Microsoft Corp., OS/2 is an Operating System for microcomputers using either the Intel 80286 or 80386 microprocessor chips. It is the hopeful successor to DOS, also developed by Microsoft for IBM. OS/2 uses the "protected mode" operation of the CPU to expand memory from 1 to 16 megabytes and for fast, efficient multitasking. Three major components make up OS/2. At the center of the operating system is the OS/2 "kernel". It is responsible for maintaining files, managing several programs that may be running simultaneously, and allowing these programs to communicate. As the second major component of OS/2, the Presentation Manager extends the multitasking capabilities of the kernel in order to run simultaneously on the same screen, each program occupying its own window. The Graphics Programming Interface (GPI), as the third major component, provides OS/2 with a powerful graphics system. =The OSI (Open System Interconnection) model is a reference model defined by the International Standards Organization (ISO). It is a communications protocol consisting of seven layers intended as a standard for the development of communications systems worldwide. The seven layers of the OSI Model are as follows: 1. - Physical Layer wires, plugs, and electrical signals 2. - Data Link Layer packaging of data for transmission 3. - Network Layer connections between two separate systems 4. - Transport Layer conversion for transmission over network 5. - Session Layer establishes and terminates the session 6. - Presentation Layer data format conversion 7. - Application Layer messages between application programs "An overlay is a section of a program that is temporarily stored on a direct access storage device, such as a disk drive, while another section of the same program is executing. The overlay is then loaded into main memory in the same locations occupied by the last section of the program. Overlays are used when the program requires more memory space than is available in main memory. nA packet is a group of data elements transmitted together that generally form part of a larger transmission made up of a number of packets. A packet also contains additional information such as packet number and error detecting codes. Packet switching is just a method of communication that involves splitting a transmission up into packets. Successive packets along a given channel can belong to different transmissions. A device used to create and unpack packets is called a PAD for Packet Assembler/Disassembler. Ö*A value added network offering long distance computer communications allowing the user to access a remote computer, by dialing a local node, or access point, is called a packet switching network. The packet switching networks use high speed digital links, which can be land lines or satellite communications. They use synchronous communications, usually with the X.25 protocol. The routes are con- tinually optimized, and successive packets of the same message need not necessarily follow the same path. Three of the major packet switching networks are: ARPANET, by U.S. Gov't, the first major packet switching network Telenet, operated by General Telephone Co. TYMNET, operated by McDonnell-Douglas ^7In desktop publishing, and in type-setting, composition refers to how the characters fit on the page, as well as their vertical and horizontal spacing in relation to each other. The type font and style determine the spacing between letters and words. Each character has a specific width, with built-in spacing between characters, set by the font designer. Certain pairs of characters, such as AW and Yo, look too far apart when printed with the built-in spacing. Pair-kerning is a software feature that allows for the spacing between certain characters to be adjusted before printing. p The terms PAL and SECAM both refer to systems of TV broadcasting used in Europe. The NTSC system is used in North America. None are compatible with the others. PAL, Phase Alternating Line system, was invented in 1961 and is used in England and many other European countries. With its 625-line scan picture delivered at 25 frames/second, it provides a better image and an improved color transmission over NTSC. SECAM, Sequential and Memory, is used in France and in a modified form in the USSR. SECAM uses an 819-line scan picture which provides a better resolution than PAL's 625-line and NTSC's 525. $A parallel port is a channel to which a peripheral device, such as a dot matrix printer, can be connected. With parallel transmission, the eight bits of data representing characters are transmitted over several lines. The parallel port (LPT1) on the back of IBM-compatible PCs provides a DB-25 female connector. Almost without exception, a parallel interface in a microcomputer printer will be a Centronics interface. Typically, a parallel transmission of data is faster than a serial (RS-232) transmission. [[A parity bit is a check bit appended to a unit of data to make the sum of the total bits even or odd. If the sum of all the bits that make-up a unit of data, including the parity bit, is even, then that unit of data is said to have even parity. It is considered to have odd parity if the sum of the bits is odd. A computer system is designed to assign one type of parity throughout. A parity check can be performed on a unit of data for either even or odd parity to determine whether an error has occurred in the reading, writing, or transmission of data. A parity error occurs when the sum of the bits of a unit of data is expected to be even but reports odd parity. Two types of parity checks: VRC - Vertical Redundancy Check, a parity check in transmitted data. LRC - Longitudinal Redundancy Check, a bit positional parity check. ßTo parse is to separate a sentence or phase into its parts, explaining the grammatical form, function, and interrelation of each part. For example, a person's complete name could be parsed into its first, middle, and last name parts. Another example: a computer program consists of statements that must conform to the syntax rules of the programming language. When the program is sent to the compiler, each statement is parsed during the syntax validation process. I!Pascal is a high-level programming language, named for the French mathematician (1623-1662) Blaise Pascal, designed to support the concepts of structured programming, with each program following a precise form. Pascal was developed in the early 1970's by Niklaus Wirth for teaching programming. Pascal is easy to learn and is often the first language taught in schools. Pascal is available in both interpreter and compiler form and has more type-checking and other safety features than does the C-Language but is generally acknowledged to be less powerful than C. ’BA pathname is a route through the file system that leads to a file. There are two kinds of pathnames: relative and absolute. Relative pathnames start in the current directory and lead to a file either residing in the current directory or in a subdirectory. Absolute pathnames start in the root directory and always refer to the same file, no matter where you are in the file system. ë"PC Forth is a programming environment written specifically for the IBM-compatible microcomputers. It is actually a superset of the Forth-83 Standard which runs on mini and mainframe computers. Like other Forth programming environments, it consists of more than just a programming language. It includes an operating system, an editor, an assembler, an interpreter, a compiler, a high-level language, and a set of development tools or utilities. Forth was designed and written principally by Charles H. Moore in the 1960's. In 1976, Forth was made the standard language for the International Astronomical Union. For additional information on the Forth programming environments, contact the San Diego Forth Interest Group. Ð?PC, Personal Computer. The IBM PC microcomputer, introduced in 1981, featured an Intel 8088 microprocessor chip, and two 360K floppy disks. PC-XT, Personal Computer - Extended Technology The IBM PC-XT microcomputer, introduced in 1983, featured an Intel 8088 microprocessor chip, and a 10 MByte hard disk. PC-AT, Personal Computer - Advanced Technology The IBM PC-AT microcomputer, introduced in 1984, featured an Intel 80286 microprocessor chip. ±lA Personal Computer is a type of microcomputer, moderately priced and intended for an individual user at home or at the office. It is used for a variety of tasks such as home management, accounting, education, record keeping, programming, telecommunications, and entertainment. Adding a modem and the use of a telephone line, a personal computer becomes a link to the outside world, capable of retrieving information from any of the many public and private host computers. The term Personal Computer or PC was selected by IBM as a name for its first microcomputer product, the IBM-PC. Today, 'PC' is a general term which applies to a wide variety of small computers. 0PCB is an abbreviation for Printed Circuit Board. A printed circuit board consists of a thin layer of copper bonded to an insulating board made of phenolic or fiberglass. When immersed in a chemical etching bath, the copper is dissolved away, except on those areas of the board that have been coated with a material that resists the action of the etchant. The copper left on the board forms the wiring of the circuit. A printed circuit is an electronic circuit that is etched, vacuum deposited, or electroplated on a flat insulating sheet. >The Personal Computer Memory Card International Association and the Japanese Electronic Industry Development Association developed a standard for integrated circuit cards called PCMCIA 2.0. PCMCIA 2.0 establishes a standard for input/output cards and creates a new I/O bus for portable computers. The cards are about the size of a credit card, 85.6 by 54 mm, and are plugged into portable and pen-based microcomputers. Cards from different manufacturers, if they conform to the standard, can be interchanged between computers. The cards are lightweight, small and rugged, and are used for a variety of functions. Intel has a 2MB flash memory card. There are modem and network interface cards. Other card peripherals for portable computers will soon appear. ²%From the Latin term, perforatus, to bore through. Perfory refers to the rows of holes along the edges of continuous fan-fold computer forms to allow the paper to be advanced or fed into a printer with a tractor feed or pin feed mechanism. After the output from the computer is printed, the perforated edges can be removed. Pin feed is a paper movement method that operates with a set of pins on a platen or tractor. The pins engage the paper through holes along the perforated edges on the left and right borders. Printers and plotters often are equipped with a pin feed mechanism for pulling paper into use from a roll or a continuous fan-folded stack of paper. +/Any external hardware device used for input/output operations with a computer system is referred to as a peripheral device. Printers, tape drives, external modems, keyboards, plotters, scanners, and digitizing tablets are all examples of peripheral devices. When a peripheral device is connected and powered is applied, it is said to be enabled. When a peripheral device is enabled and recognized by the operating system, it is said to be on-line. In other words a device could be connected and enabled but not necessarily on-line. ­kIntroduced by IBM in 1984, the Professional Graphics Adapter was designed for unusually demanding circumstances, such as Computer Aided Design applications. It had its own microprocessor built into it, more powerful than the computer it was installed in. At the time the PGA provided the highest resolution with the most number of colors (256), but was so expensive and specialized that it never gained popularity. /A picosecond is one trillionth of a second, abbreviated PSEC. A picosecond is one thousandth of a nanosecond. Pronounced 'pee-koh', the combining form 'pico' is probably derived from the Italian word piccolo for small and is used to designate ten to the minus twelfth power. s1PIF is an abbreviation for a Program Information File. A PIF is a special file containing settings that tell Microsoft Windows how to execute a non-Windows application. If a PIF is not found for a particular application, Windows starts the application using the standard settings. In fact, many programs never need a PIF. PIFs can be created using the PIF Editor in the Accessories Group within the Windows environment. Each PIF contains two sets of options. The Standard options are for running the application with Windows in real or standard mode. The 386 Enhanced options are for the 386 enhanced mode. 4)A pipe is a conduit or mechanism that allows the output of one process to be used as the input to another process. With operating systems, a pipe is a portion of memory that can be used by one process to pass information to another. With DOS and OS/2, pipes are symbolized by the | character embedded in a command. For example, the command DIR | SORT | MORE calls for a directory listing, pipes the output to the sort command, and pipes the result of the sort command to the more command, which displays its output on the screen, one page at a time. íA pit is a microscopic depression in the reflective surface of a CD-ROM disc. The pattern of pits on the disc represents the data that is stored. The un-pitted area between pits is called a land. The tiny laser beam used to read the data from a CD-ROM disc is reflected from the lands, but scattered by the pits. A typical pit is about the size of a bacterium, 0.5 by 2.0 microns. The term pit is broadly used to refer to any type of data- carrying mark in optical media. fA contraction of PICtureS ELement, a pixel is any of the tiny rectangular elements that form a digitized picture on a video display screen. Each pixel represents the degree of brightness assigned to that point in the picture. A pixel is also called a pel. Pixel doubling is a method of changing the aspect ratio of a display by duplicating rows or columns of pixels. Pixel thinning is a technique for reducing the bandwidth or changing the aspect ratio of an image by systematically discarding pixels. (The term platform refers to the hardware architecture, the foundation technology of a particular computer family. It is also somewhat of a standard to which software applications are written. For example, this program was designed and written to run on the IBM-PC microcomputer platform. nA plotter is an output peripheral device attached to a computer for making drawings. There are basically two kinds of plotters, flatbed and drum. A flatbed plotter makes a drawing on a piece of paper placed on the bed so that the drawing device (an ink pen or pens) must be moved along the horizontal and vertical axes. The size of the drawing is limited to the size of the flat bed. A drum plotter makes the drawing from a long roll of paper of a fixed width. The roll of paper is fed forward and backward with a tractor feed mechanism as the pen moves left and right across the paper in one axis. ¹$A pocket modem is a portable hardware device that plugs into a computer's serial port to provide data communications over the telephone lines. These units typically have a DB-25 connector on one end and a standard RJ-11 telephone jack on the other. Pocket modems are often smaller than a pack of cigarettes, weigh less than half a pound, and can transmit data at speeds up to 2400 bps. An important consideration in selecting a pocket modem is its source of power. Some draw their power from the computer's battery or AC while others are equipped with their own power adapter that plugs into a wall socket. There are even some that get their power from the telephone line. In the new world of desktop publishing many of the terms are inherited from the typesetters. Inches are widely used in setting up page sizes and margins, but the technical units of measure are points and picas. The point system of type measurement was invented in 1737 by a French typographer named Pierre Simon Fournier, and it became an international standard. Each point is precisely .013837 inch, which means there are 72 points to the inch. Measurements of type height and the space between lines of type are expressed in points. Larger measurements, such as the width of a column or page, are expressed in picas. One pica equals 12 points. Since there are 72 points to the inch, and 72 divided by 12 equals 6, there are 6 picas to the inch. ÎKA portable computer is a type of microcomputer that is designed to be easily transported from one location to another. The first portable computer was the Osborne I, a CP/M-based 8-bit machine, that was soon followed by many others, such as the Kaypro, Hyperion, and Attache. In 1982, Compaq Computer introduced the first IBM-compatible portable computer. Even at thirty pounds, it was very successful. Today, portable computers use flat-panel display screens and weigh from six to twenty pounds. Generally, portable computers are not solely battery operated, although some may have that option. Portable computers having self- contained rechargeable batteries are called laptops or notebook PCs. CThe terms portrait and landscape refer to the orientation of the output on the printed page. Word processing programs often will offer the option of printing in one of these two modes. The portrait mode prints the regular way, so that the longest edge of the form corresponds to the vertical axis. ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ ³ LANDSCAPE ³ ³ PORTRAIT ³ ³ ³ ³ ³ ³ ³ ³ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ³ ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ The landscape mode prints sideways. Øc"Point of Sale" refers to the process of capturing product information at the time and place of the sales transaction. The two best advantages of Point of Sale systems are the reduction of data entry errors and immediate inventory updating. A Point of Sale system often includes an optical scanning device for reading OCR characters or bar codes printed on the product package. Magnetic card readers are also used to read the magnetic strip on the back of credit cards. The information that is collected by the Point of Sale system can be transmitted to a central computer immediately or at the end of some accounting period, often daily. These systems are rapidly becoming more and more sophisticated. Ü9Both the IBM Micro Channel and the Apple NuBus define high-level mechanisms to integrate cards or devices into their bus systems. This eliminates the need for jumpers or DIP switches to set either a card's interrupt level or its address space, which is the cause of a lot of bus problems on typical microcomputer systems. The Micro Channel's Programmable Option Select eliminates DIP switches from the system board and adapters by replacing them with programmable registers. Automatic configuration routines store the POS data into a battery- powered CMOS memory for system configuration and operations. The configuration utilities rely on adapter description files that contain the set-up data for each card. ‹$Every time your microcomputer system is powered-on, it undergoes a series of hardware checks to insure that it is working properly. This set of diagnostic routines is called the Power-On Self-Test, and generally, is completed within 30 seconds. During system start-up, the POST tests the primary system board components such as the CPU, the DMA controllers, and the interrupt controllers. Adapters with on-board ROM modules are initialized. The video controller card is tested and initialized. The cursor is positioned at the top left corner of the screen. All memory chips (RAM chips) are tested with read, write, and verify checks. The keyboard is reset and tested. Disk interrupts are enabled. Finally, the POST ends with a beep from the speaker and passes control to the bootstrap loader which loads the operating system from a floppy disk drive or from the hard disk drive. “JPostScript is a page description language developed mainly by John Warnock for converting and moving data to the laser-printed page. Instead of the antiquated method of transmitting simple information to a 'dumb' printer, telling it where to place dots one-by-one on a page, PostScript provides a way for the laser printer to mathematically interpret and enhance a full page of shapes and curves. There are many advantages of using a page description language instead of bit-mapped graphics, such as smoother lines and curves, full use of printer resolution, and the capability to process complex fonts. Several languages have been developed, but only PostScript really caught on in the market and became the standard in page description. Invisible to the user, PostScript kicks in at print time and processes a document so that it takes full advantage of 300-dpi (and higher) laser printers. 8FIn mathematics, logic, and with programming languages it is necessary to define a set of rules governing which operations are to be performed first. In an algebraic equation, if an expression is enclosed in parentheses, that expression is evaluated first according to the rules. For example, 4 x (2 + 6) = 32, but 4 x 2 + 6 = 14, where the multiplication operator (x) is performed before the addition operator (+). Precedence then is a priority or hierarchy scheme for operators. Operators used in programming languages have an inherent precedence; that is, in the absence of explicit grouping (through parentheses), the order of evaluation of an expression depends upon the precedence of the elements involved. Operators of higher precedence are evaluated before operators of a lower precedence. ^kProdigy is an on-line service founded in 1988 as a joint venture between Sears Roebuck and IBM. It provides a graphical interface with CGA resolution. Commercial advertising appears on most screens. Services include: interactive multi-player games, on-line shopping, news, weather maps, research capabilities, and many family-oriented features. All messages submitted to the bulletin boards by users are edited by Prodigy to conform to its standards of good taste. For current fees and more information, Prodigy Services Co. 914-962-0310 445 Hamilton Avenue White Plains, NY 10601 æ,An acronym for PROgramming in LOGic, PROLOG is a high-level logic-based programming language used in the development of artificial intelligence applications, such as natural language, expert systems, and abstract problem solving. PROLOG is designed to manipulate knowledge instead of numbers. It is composed mainly of common English words and uses these words to describe facts, relationships, and patterns in a logical, concise fashion. What distinguishes PROLOG from the traditional procedure-oriented programming languages is that each line of PROLOG includes both instructions to and data to be managed by the computer. PROLOG was developed in France in 1973 by Alain Colmerauer at the University of Marseilles. š`PROM is an acronym for Programmable Read Only Memory, it is a type of memory chip that can be programmed to a customer's needs. The programming is done by blowing selected fuses in order to obtain a desired bit pattern, a process called blasting. A PROM chip can be programmed only once and is non-volatile memory. An EPROM is an Erasable PROM, erased under high-intensity ultraviolet light, then reprogrammed. An EEPROM is an Electrically Erasable Programmable ROM. It is a non-volatile storage chip. Since its contents can be erased and then re-written under software control, it functions like a RAM chip but is slower and more expensive. ÃlProtected memory is a property of the 80286, 80386, and 80486 Intel microprocessors that allows it to safely and reliably expand the number of programs the CPU can be working on at one time. That is, the protected mode allows for multitasking. Protected memory is dynamically defined by the operating system to erect barriers to prevent a program from interfering with the operation of other programs or with the operating system itself. ë6Excluding the Intel 8088, the family of 8086 microprocessors have two modes of executing programs, real and protected mode. In the real mode of operation, the 80286, 80386, and 80486 CPUs act like the 8086 CPUs and execute programs one at a time in 640 K of conventional memory. In real mode, a misbehaved program could interfere with some other program causing the CPU to halt. In protected mode, the CPU can safely and reliably execute more than one program at a time. This is accomplished by the operating system through four main facilities; protection, extended memory, virtual memory, and multitasking. In protected mode, DOS erects barriers to prevent a program from interfering with the operation of any other program. ‹8A protocol is a set of rules governing the communication and the transfer of data between two or more devices. The rules define the handling of certain communication problems, such as framing, error control, sequence control, transparency, line control, and start-up control. There are three basic types of protocol: character oriented, byte-count oriented, and bit oriented. UThis chart shows the PS/2 line of personal computers designed by IBM and introduced in 1987. Models 50 and above feature the MCA bus. ÚÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄ¿ ³ Models ³ CPU ³ Speed MHz ³ RAM ³ Hard Disk, MB ³ Slots ³ ÆÍÍÍÍÍÍÍÍÍØÍÍÍÍÍÍÍØÍÍÍÍÍÍÍÍÍÍÍØÍÍÍÍÍÍÍÍÍÍØÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍØÍÍÍÍÍÍ͵ ³ 25 & 30 ³ 8086 ³ 8 ³ 512/640K ³ None & 20 ³ 2 & 3 ³ ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄ´ ³ 50 ³ 80286 ³ 10 ³ 1 MB ³ 20 ³ 3 ³ ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄ´ ³ 60 ³ 80286 ³ 10 ³ 1 MB ³ 44,70,115 ³ 7 ³ ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄ´ ³ 70 386 ³ 80386 ³ 16,20,25 ³ 1 or 2MB ³ 60 or 120 ³ 3 ³ ÃÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄ´ ³ 80 386 ³ 80386 ³ 16 or 20 ³ 1 or 2MB ³ 44 to 314 ³ 7 ³ ÀÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÙ ¸!In reference to software, public domain refers to one of the types of freely-distributed programs. When the author or programmer of a piece of software retains no legal rights, and has not attached a copyright notice, it is then referred to as "public domain". Some public domain programs have been copyrighted but do not request a fee for continued use. Anyone may use public domain software and freely pass it on to others. $JA pull-down menu is a window menu on the display screen that appears to be pulled downward or expanded when an item is selected from a line-bar menu. Menu items can be selected either with a mouse or with the enter key. This PC-GLOSSARY program does not make use of pull-down menus. âInformation stored in a database file can be retrieved in a number of different ways. In most cases, the database application program that was used to create the database also provides a means to selectively retrieve the information, by describing a procedure for finding the information. When the operator is able to define the qualifications for selected records by specifying an example, the interactive process is called Query By Example. Originally, QBE as a 4th generation language was defined by M. Zloof of IBM in the late 1970's in his paper, "Query-by-Example: A Database Language." Today, the term is used generically to describe similar interfaces. dBASE IV and Paradox provide interfaces in the QBE style. ü#QIC is the most common width of magnetic tape used in personal computer tape backup systems. The width of the tape is a quarter of an inch. The QIC cartridges come in several physical sizes. The size of the cartridge depends on the length, capacity, and thickness of the tape stored inside it. Capacities vary from 40 megabyte to 1.35 gigabyte. QIC is typically used as a prefix for a number of standards used to promote interchangeability among tape drives from different manufacturers. kQuartz is a mineral, silicon dioxide, occurring in abundance. It is a brilliant, hexagonally shaped crystalline mineral. For use in electronics, a quartz crystal is created by accurately grinding and finishing a thin plate or rod of quartz. When an electrical current is applied, the quartz crystal vibrates at a particular frequency. Every computer system utilizes a quartz crystal to regulate the system clock. When the machine is turned on, electric current causes the precisely cut sliver of quartz crystal to deform or vibrate, at a constant rate, millions of times per second. A voltage pulse is emitted with each vibration which, along with other signals, controls the pace of action and ensures that the circuits do not get out of phase. yNPronounced "Q", a queue is a list or temporary holding place for data. It allows for insertions at one end and deletions at the opposite end. Items in a queue are usually processed on the first-in, first-out principle. A print queue is a buffer or holding area for temporarily storing output data directed for the printer until the printer is ready to print it. Z The standard typewriter or computer keyboard, with the characters "Q, W, E, R, T, and Y" on the top row of letters as shown below. ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄ¿ ³ ³³ Q ³³ W ³³ E ³³ R ³³ T ³³ Y ³³ U ³³ I ³³ O ³³ P ³³ ³³ ³³ ³ ÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙ³ ³ ÚÄÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄÙ ³ ³ ³³ A ³³ S ³³ D ³³ F ³³ G ³³ H ³³ J ³³ K ³³ L ³³ ³³ ³³ ³ ÀÄÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÄÄÄÙ ÚÄÄÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄ¿ÚÄÄÄÄÄÄÄÄÄÄ¿ ³ ³³ Z ³³ X ³³ C ³³ V ³³ B ³³ N ³³ M ³³ ³³ ³³ ³³ ³ ÀÄÄÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÙÀÄÄÄÄÄÄÄÄÄÄÙ ÚÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄ¿ ³ ³³ SPACE BAR ³³ ³ ÀÄÄÄÄÄÄÙÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙÀÄÄÄÄÄÄÙ The QWERTY keyboard was developed in the 1800's to slow-down swift typists and to prevent jamming of the old mechanical typewriters. §*Random Access Memory is the type of semiconductor-based memory on a chip in which any location can be accessed directly without having to follow a sequence of storage locations. RAM is volatile, that is, when the power is turned-off, the data is lost. 'Random access' refers to the ability to call up any location in memory in the same access time, regardless of which memory location was last accessed. Although the data stored in ROM memory chips can also be retrieved in a random fashion, ROM chips retain their data even after the power is off. The term RAM is generally understood to refer to volatile memory, in which data can be written as well as read. 9^A RAM disk is an area of memory that has been defined for temporary storage of programs and/or data. A device driver is used to set-up and access the data in this area in a manner similar to a hard disk but much faster. If your computer has extended memory (above 1 megabyte), or if it has an extended memory board that meets EMS, you can use this area for one or more RAM disks. Otherwise, a RAM disk can be built in conventional memory. When the system is re-booted, or when the power is turned off, the information stored in RAM disks is lost. bThe process of obtaining data from or placing data into a storage location independent of the order of storage is called "random access". For example, disk files can be created with pointers or indexes such that data can be directly read from any location in the file without having to start at the beginning of the file. With memory chips (RAM), random access refers to the ability to call up any location in memory in the same access time, regardless of which memory location was last accessed. ëxExcluding the Intel 8088, the family of 8086 microprocessors have two modes of executing programs, real and protected mode. In the real mode of operation, the 80286, 80386, and 80486 CPUs act like the 8086 CPUs and execute programs one at a time in 640 K of conventional memory. In real mode, a misbehaved program could interfere with some other program causing the CPU to halt. In protected mode, the CPU can safely and reliably execute more than one program at a time. This is accomplished by the operating system through four main facilities; protection, extended memory, virtual memory, and multitasking. In protected mode, DOS erects barriers to prevent a program from interfering with the operation of any other program. YA record is a group of data fields used to store information about a particular subject. A collection of records makes up a database file. The example shown here contains four records. ÚÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄ¿ ³ Record No. ³ Name field ³ City field ³ State ³ ZIPCODE ³ ÃÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄ´ ³ 1128 ³ Zeek Branlon ³ St.Petersburg ³ FL ³ 33710 ³ ³ 1946 ³ Jim Hoff ³ Greenhills ³ OH ³ 45218 ³ ³ 1948 ³ Dale Elrod ³ Medora ³ IN ³ 47260 ³ ³ 191 ³ Roy K. Ahuna ³ APO San Fran ³ CA ³ 96370 ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÙ The record number is not necessarily part of the record but serves as a reference and is often transparent to the user. jRecord locking is a data protection scheme used by database management systems (DBMS) to preserve data integrity in a multi-user operating environment such as a local area network (LAN). With record locking, it is not necessary to lock the entire database for exclusive use by a single user, only the record being updated is locked. This allows other users to make changes to other records in the database simultaneously. Early data protection schemes used file locking to prevent two or more simultaneous update operations on a single file. Even better than record locking, field locking schemes restrict access only to the particular field being used. But field locking is extremely difficult to implement and imposes a tremendous load on the operating system. MReferential integrity is a desirable feature of a Database Management System. It ensures that cross-references between tables are always valid. This is done by enforcing that foreign key values match existing values in primary keys. A primary key uniquely identifies a single row within a table and can consist of one or more columns, none of which can be null. Foreign keys point to or reference primary keys and must match those of the primary key one for one. An example would be a check to ensure that a customer in the database cannot be deleted if orders exist for the customer. The advantage of defining a check like this within the database is that the database can enforce the check for every different kind of transaction. Thus, it needs only to be written once. 'Memory registers are high-speed memory circuits that are integral parts of the Central Processing Unit (CPU) chip. They are system addresses for storing program instructions, data or addresses to data during the execution of a program. Assembly language programs make frequent use of the memory registers during execution to keep track of program flow and data. When a program halts or crashes, the contents of the registers at the instant of the failure will provide the programmer with clues to the cause of the problem. ¼ Resolution refers to the capability of an optical system, such as a video screen, or of a scanning device such as an OCR, or of a printer, of making clear and distinguishable the separate parts or components of an object. In video graphics, the resolution refers to the number of pixels in which the display area can be divided, determined by the number of horizontal and vertical pixels. For example, a resolution of 640 by 200 pixels indicates a display area with 640 pixels across the screen and 200 pixels vertically. The greater the resolution, the more display memory is needed to produce the screen image. With high resolution printers, the output is "Letter quality". PeA rewritable optical disk drive is a computer peripheral device for storing large amounts of data, up to 650 megabytes on a removable cartridge. Of the three rewritable optical technologies employed today, magneto-optical is the most developed and successful. It differs from the traditional magnetic media in that the read/write heads are replaced with an optical system. Information is actually stored onto a thin magnetic film as ones and zeros similar to the traditional hard disks, but during the read operation, the data is read with optical lasers. Although rewritable optical disk drives are much slower and more costly than the traditional hard disks, they have other benefits. The cartridges can be easily removed for safe keeping. Rewritable optical disks are virtually free from self-erasure and head crashes. ]=REXX is a structured, procedural computer language that offers multiple benefits not typically found in a single language. It is used for batch, executive, and command programming. It is an interpreted language that is readable and easy to learn. REXX was created by M. F. Cowlishaw in 1979, at the IBM-U.K. research laboratory near Winchester, England. It now works across a worldwide network of IBM mainframes, minicomputers, and PCs. It has been blessed by IBM as the command procedures language of SAA, System Application Architecture. As a commercial language, REXX was introduced as a system command interpreter for the Conversational Monitor System (VMS) on IBM mainframes in 1983. REXX migrated to the IBM PC as Personal REXX in 1985, published by Mansfield Software Group. V2.0 supports both DOS and OS/2 in the same package. 4Microcomputers emit radiation that can interfere with television reception, emergency communications, air traffic control, and other services using electronic devices. The Federal Communications Commission (FCC) is trying to regulate the computer industry and protect the electromagnetic spectrum. The most potent source of Radio Frequency Interference from a microcomputer is the crystal that controls the microprocessor's clock speed. But other components of a computer can cause RFI, such as, the monitor, the keyboard, and the power supply. IA color monitor that accepts input in the form of discrete signals for the Red, Green, and Blue guns is called an RGB monitor. On a television or color monitor, colors are displayed as varying intensities of red, green and blue dots. With all those colors turned-on high, white is produced. As the intensities are equally lowered, shades of grey are produced. Late model RGB monitors are available in both analog and digital varieties and can function as a computer monitor or as a television receiver. K$RISC is a acronym for Reduced Instruction Set Computer as differentiated from CISC, Complex Instruction Set Computer. Reduced instruction set does not mean fewer instructions, but rather a return to simple instructions requiring only one or a few execution cycles that are utilized more effectively under innovative architectural and compiler changes. As computing technology evolved, instruction sets expanded to include newer instructions which are complex in nature and require several to many execution cycles and, therefore, more time to complete. Computers that operate with system software based on these instruction sets have been referred to as complex instruction set computers (CISC). Systems utilizing RISC technology are able to achieve processing speeds of up to nearly 5 million instructions per second. À4RJ-11 and RJ-45 are designations for commonly used modular telephone line connectors. RJ is an abbreviation for Registered Jack. Both of these connectors serve as an interface between the telephone line and the receiving device such as the telephone or a modem. They consist of a plastic plug on the end of a wire and a jack on the phone, modem, or wall plate. The RJ-11 consists of six wires and is used for the standard telephone voice line connection. The RJ-45 consists of eight wires and is typically used for data transmission over twisted-pair telephone wire. There are also connectors such as the RJ-16, RJ-21, RJ-27, RJ-36, and RJ-41 for other telephone line applications. ¶A variety of techniques or schemes exist for writing or encoding data to a hard disk drive. The term Run Length Limited derives from the fact that the techniques limit the distance (run length) between magnetic flux reversals on the disk platter. There are several types of RLL encoding techniques: (1,7)RLL encoding increases storage capacity 25% over MFM encoding. (2,7)RLL or Enhanced RLL (ERLL) encoding increases storage capacity by 50% over MFM encoding. (3,9)RLL or Advanced RLL (ARLL) encoding roughly doubles that of MFM. An RLL certified hard drive can use an MFM controller card but the storage capacity and the data transfer rate will be reduced. cRobotics is the area of artificial intelligence dealing with the creation and use of stand-alone hybrid computer systems, called robots, that perform physical and computational activities. Robots are equipped with sensing devices for detecting changes in its operational environment, a calculating mechanism for making decisions, and with a guidance mechanism for directing its physical actions. Robots are used extensively in manufacturing, performing such repetitive tasks such as welding, painting, and riveting. Î:Read Only Memory is the type of memory chip that can be read but cannot be written on or altered. ROM provides permanent storage for program instructions and is most often used in microprocessors that always execute the same program such as an electronic game. ROM's are prepared by the manufacturer and cannot be altered once the chips are made. ROM is non-volatile, that is, the data stored in ROM remains even after the power is turned-off. O The root directory is the base level of the directory structure. Branching from the root are various subdirectories, each of which can contain one or more files and subdirectories of its own. Individual files can also reside at the root directory level. With DOS, the root directory of every disk drive is identified with the backslash character (\) and is the main directory on that drive. For example, C:\ represents the root directory of drive C: At the DOS prompt, to change your current directory to the root directory of drive C:, enter the following command. CD\ ç A router is an interconnection device that links complex networks together at the network layer of the OSI model. Routers are similar to bridges between networks but generally are more active. They are capable of reading the network addressing information and selecting an appropriate travel path. Modern routers can handle multiple protocol stacks simultaneously and move packets or frames onto the right links to their proper destination. A brouter is a bridge-router operating at the data link layer of the OSI model. It performs the functions of a bridge between similar networks but remains independent of higher protocols. Like a router, a brouter can manage multiple lines and transmits messages accordingly. ÔIIntroduced in August of 1969 by the Electronic Industries Assoc., the RS-232 interface standard provides an electrical description for connecting peripheral devices to computers. Although the standard specifies a 25-pin connector, not all RS-232 devices use them. For example, the IBM PC/AT uses a 9-pin connector. The RS-232 standard defines two types of interfaces, Data Terminal Equipment (DTE), and Data Communication Equipment (DCE). Personal computers are almost always configured as DTE devices while a device like a modem or mouse is typically configured as a DCE device. When connecting two like devices, DTE to DTE or DCE to DCE, you must use a null modem cable or modem-eliminator adapter. ÆZRTF is an abbreviation for Rich Text Format, it is a file format defined by Microsoft as an adaption of the Document Content Architecture (DCA) format. RTF and DCA formats are used for transferring text documents between applications, even those applications running on different platforms. For example, a word processing document created with Microsoft Word could be converted to the RTF format and transferred to an Apple Macintosh system. ÿA scanner is a peripheral device connected to a computer to capture graphic images from a page and convert the data into a binary code. Once captured, the image can be edited with a painting program, pasted into a desktop publishing document, or sent over the telephone lines with a facsimile device. There are four basic types of scanners; sheet-fed, flatbed, overhead, and handheld scanners. With the sheet-fed variety the original is fed through the scanner by a set of rubber rollers. More advanced flatbed scanners require that the original be placed on a glass stage while the scanner optics take a picture of the stationary page. Flatbed scanners can accept originals of just about any thickness and can scan from books and magazines. ckTo advance (or go back) a specified number of lines in a file or to reposition a graphics image that is being presented on a display screen. Scroll arrow A scroll arrow is an icon that appears on the video display screen indicating the directional movement available to the operator with either a mouse or the cursor control keys. Scroll bar A scroll bar is a horizontal or vertical indicator on the screen showing the relative position of the current screen with respect to the overall picture. Some scroll bars contain a box that can be used with a mouse for scrolling the screen. Á=Small Computer System Interface is a standard developed by Shugart Associates and approved by ANSI in 1986. The parallel SCSI (pronounced scuzzy) permits faster data transfer than is possible under the common serial ST506 interface used for most PC-compatible hard disks. SCSI uses a 50-pin connector and permits multiple devices (up to seven disk drives and/or tape drives) to be connected in daisy chain fashion. With a SCSI port, parallel data transfer occurs at speeds averaging up to 4 megabytes per second. A former name for SCSI was SASI (Shugart Associates System Interface) The SCSI-2 bus became available in the early 1990's. See the Table "Disk Data Transfer Rates". îTAn SDF type file is simply a fixed-length ASCII text file commonly used to transfer data from one computer application to another. For example, in the dBase programming environment data files can be input and output using this format. Each record in the file or database is of the same length, regardless of the amount of data in the fields that make-up each record. The following generic dBase command will create an SDF type file: COPY FILE DATA.DBF TO DATA.TXT TYPE SDF ·|The SDLP specification allows software application developers to easily interface all of the popular operating systems to multiple peripherals that have similar but different SCSI interfaces, such as CD-ROM devices. ÚÄÄÄÄÄÄ¿ ÚÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄ¿ Operating System ³ Unix ³ ³ DOS ³ ³ Novell ³ ³ OS/2 ³ Protocol Level ÀÄÄÄÂÄÄÙ ÀÄÄÂÄÄÙ ÀÄÄÄÂÄÄÄÄÙ ÀÄÄÂÄÄÄÙ ÚÄÄÄÁÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄ¿ Standard Device ³ SDLP Interface ³ Level Protocol ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÙ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÁÄÄÄÄÄ¿ Interface ³ SCSI ³ ³ ESDI ³ Protocol Level ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÂÄÄÄÄÄÙ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ ³ disks, optical devices ³ ÚÄÄÄÄÁÄÄÄÄÄ¿ Controller ³ host adapters, tape units ³ ³ disk ³ Protocol Level ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÙ ª4A computer of the second generation is classified as beginning from the late 1950's and early 1960's. It is characterized by physically smaller units that produced less heat and required less power because they used solid state transistor circuitry, and that used disks as well as tape for auxiliary storage. From the early 1960's, the IBM 1401 and the Honeywell 400 are examples of second generation computers. ‡aA sector is an equally spaced division of data within each track of a disk and is the smallest unit of storage read or written by the disk drive. Each track consists of the same number of sequentially labelled sectors. Thus, sector three follows sector two on each track, and so on. Sectors may be referred to as either physical sectors or logical sectors. Physical sectors are the actual, sequentially numbered divisions of the disk. Logical sectors are those that the operating system reads and writes in sequence, a scheme that is determined by the disk's interleave. Floppy and hard disk sectors are 512 bytes long. ÷7Generally, a segment is any of the parts into which a body is separated. It refers to any partial component of a larger structure. A segment is a portion of a computer program that may be executed as an entity without the entire program being loaded. In computer graphics, a display segment is a collection of elements, such as dots, arcs, or lines, that can be manipulated as a group. With LCD and LED displays, a segment refers to one of the bars that make up a single character. PA self-extracting program is one that has been created so that when it is executed, it creates from itself one or more smaller programs and/or data files which have been compressed inside the program. Software developers often store and distribute programs in this manner, thereby saving valuable hard disk space and reducing the amount of time needed to transfer program files to other computers. Self-unARCing is a another term that also refers to the process of extracting data from a file created with the archive program called ARC from System Enhancement Associates. oFA semaphore is a programming or software term. A semaphore is often a flag variable used to indicate whether a shared resource can be accessed. Semaphores are also useful in providing synchronization between two or more threads or processes that are being executed at the same time. Multitasking operating systems, like OS/2, make use of semaphores. É~A semiconductor is a substance, such as germanium or silicon, whose conductivity is poor at low temperatures, but is improved by minute additions of certain substances or by the application of heat, light, or voltage. Depending on the temperature and pressure, a semiconductor can control a flow of electricity. It is the material from which integrated circuits are made. Semiconductors are the basis of modern electronic circuit technology. c When a file must be read serially from the beginning to the end, it is described as being a sequential access file. For example, magnetic tape files must be searched serially from the beginning to find the desired record. Data from disk files can be read in a sequential or random manner depending on how the file was designed and written. Ý3An asynchronous communication port or channel or address to which a peripheral device, such as a character printer or a mouse, can be connected. Serial ports are also referred to as COM ports, (COM1, COM2, etc.) With serial communications, bits of data are transmitted one at a time over a single line as opposed to parallel communications where multiple wires in the cable allow data to be sent in multiple bits. Serial interfaces are also called RS-232. Y{With random access memory (RAM), stored information can be accessed directly and quickly without having to follow a sequence of storage locations, regardless of which memory location was last accessed. The system BIOS (Basic Input/Output System) is responsible for handling the details of the input and output operations, including the task of relating a program's logical records to a peripheral device's physical records. Shadow RAM is a technology that loads the system BIOS and/or video BIOS into RAM during the boot procedure, thereby allowing the BIOS to operate much faster. ÃJShareware is a distribution method for software programs developed by independent programmers or authors. It is a marketing technique rather than a type of software. It allows the author to market the program with minimal start-up expenses while encouraging feedback from the users. Programs acquired through the Shareware method may be freely copied and passed on to others, but each user is expected to register with the author and pay a usage fee. The fee may include some or all of the following: printed documentation, the latest version of the program on disk, telephone support, free updates, and commissions, but most importantly a legal license to continue using the software. O2A sheet feeder is a mechanical device that feeds individual sheets of paper into a printing device, one at a time. Sheet feeders are available for standard and legal size forms and are commonly found on copy machines and computer printers. Envelopes can even be used with sheet feeders for printing names and addresses. SdIn reference to software, the term 'shell' refers to the specialized program that allows the operator to enter commands and access the system resources. Known as the command processor, or shell, it is simply a user interface to the operating system, not the operating system itself. For example, the familiar default command processor for DOS is COMMAND.COM. You can change the default shell for DOS with the following statement in the CONFIG.SYS file. SHELL=C:\DEBUG.COM, and you will be presented with the DEBUG dash prompt instead of COMMAND.COM's familiar prompt. But since DEBUG wasn't written as a shell, when you quit, your system will be hung-up. Another example: The OS/2 shell program that loads when you boot is called the Program Selector. You start OS/2 sessions or run the DOS box from the Program Selector. 9OA Special Interest Group consists of a number of people within a larger organization who share the same interest in a particular topic or subject. Special interest groups often hold their own meetings, sponsor exhibits, publish documents, and/or administer forums related to their special topic. Computer clubs and Bulletin Board Systems most often will have SIG'S for members interested in applications such as spreadsheet, database, programming languages, genealogy, communications, desktop publishing, accounting, CAD/CAM, networking, and others. ËgMemory chips are available in a variety of styles: The Single In-line Package (SIP) is a single package array of computer chip logic assembled so that all the connecting legs are in a straight line, like the teeth on a comb. The Dual In-line Package (DIP) is the traditional computer chip with 8, 14, 24 or even 40 or more metal legs or prongs, evenly distributed on the left and right sides. The Single In-line Memory Module (SIMM) is a type of memory chip design whereby individual logic devices are installed on a printed circuit board, creating a component module that can be plugged into a larger device. A SIMM holds nine DRAM chips, eight for data and one for parity or error checking. 1mAll the programs, languages, and/or routines that control the operations of a computer are referred to as the software. The software for a computer system is most often loaded into the computer from a disk or magnetic tape but it can also be built into a computer ROM (Read-Only Memory) chip. %Making un-authorized copies of computer programs for distribution to others is called software piracy. This illegal practice is very common in the microcomputer world and has caused software developers to devise all sorts of preventive methods. But over the years, as each new copy protection scheme was introduced, a counter method was devised. By the late 1980's, copy-protected software was mostly a thing of the past. But that doesn't make it legal to freely copy software. Large software-producing corporations are very serious about trying to minimize software piracy. In fact, there is an association in Washington D.C. called the Software Publishers Association. They maintain a toll-free telephone number (800-388-7478) for the purposes of reporting software piracy. P5Along with the growth and popularity of microcomputers, especially in the mid to late 1980's, a nasty side effect also came into existence, the software virus. It is any program written expressly for the purpose of reproducing itself after or during the process of committing some act of malice on the infected system. Some virus programs immediately erase all files on a hard disk while others will lay dormant sometimes for months before causing any damage. There are, of course, programs available for detecting the presence of viral software or preventing them from infecting a system. These anti-viral programs often require continual RAM residency and can sometimes erroneously alert their owner to questionable but benign behavior of non-viral software. For more info, contact the National BBS Society, (408) 727-4559. B|When a programmer writes a computer program, the statements that make up the program are saved in a disk file. The disk file is then referred to as the source code (or source file). The term source code refers to any computer program written in any programming language. In fact, in the spoken word, programmers often refer to the source code as the source; as in "Let's take a look at the source." If the program contained in the disk file is printed to a hard copy, the output is called the source code listing, which is just another name for program listing. ¡nIn a networking environment, some token ring bridges, notably those from IBM, use an intelligent data transmission scheme called source routing for sending packets of information from a workstation on one Local Area Network to another. The packet contains routing information specifying the LANs and the bridges through which it will travel to its destination. The sending machine is responsible for putting this information in the header. Source routing diminishes network performance slightly but this is offset by the fact that the sending machine can choose the optimal path at the time of transmission. This is not possible with transparent routing. xLThe acronym "spool", for simultaneous peripheral operation on-line, was first used by IBM for its 7070 mainframe computer in the early 1960's. With microcomputers, spooling refers to a printing operation taking place in a background mode while allowing the operator to perform another task. Spooling originated with mainframe computer operations in which data on low-speed input and output devices was transferred to disk first and then fed to the central processor at high speed. Spooling programs monitor the activity of shared peripheral devices and schedule their tasks based on the priority of the data. ëA spreadsheet is a computer program that allows the user to set-up a matrix of cells and to define the relationships between all the elements. Changing a value in one cell will then alter automatically the values of all other cells that are mathematically linked to it. This degree of flexibility allows the user to play 'what-if' speculation, with the results of the experimentation visible on the screen immediately. The original spreadsheet program is called VisiCalc, conceived by Dan Bricklin, and introduced in 1978 for the Apple II computer. Other popular spreadsheet programs: LOTUS 1-2-3 Framework SuperCalc Lucid 3-D ProQube QUATTRO PlanPerfect Excel VP-Planner Plus SmartWare ÉcA battery operated device that supplies a computer system with electricity in the event of a power failure or an unacceptable voltage level, is called an Stand-by Power Supply. A stand-by power supply switches to battery backup power for a limited time so that the computer can be powered down in an orderly fashion. One of the key factors to consider before purchasing a stand-by power supply system is the amount of time required to switch to the battery backup power. Better than a SPS is a true Uninterrupible Power Supply, which always supplies power through a battery even when commercial power is available. There is no switching back and forth between battery and commercial power. 'SQL is a standard database language supporting query processing transactions, data management security, data integrity, and recovery. In the early 1970's IBM mathematician E.F.Codd described a relational database model consisting of one foundation principle and 12 related rules specifying explicit characteristics that a relational system must have. The foundation rule states that any system claiming to be relational must be able to manage data entirely through relational capabilities. Most microcomputer database products on the market today do not meet half the rules and are therefore not considered fully relational. SQL however, is used extensively on mid-range and mainframe computers and is rapidly becoming commonplace in the micro world. _%SRAM is an acronym for Static RAM and is pronounced 'ess-RAM'. SRAMs are semiconductor memory chips based on the logic circuit known as a flip-flop instead of capacitors like DRAM chips. Although the static RAM chips require power to hold their information, they do not need to be continuously refreshed like DRAM chips. SRAMs are faster than DRAMs but can only store about one-quarter the amount of data as DRAMs of the same complexity. They are more expensive than DRAM chips. Static RAM memory chips have access times between 10 and 30 nanoseconds and are often used for memory caches. &These abbreviations are found on the diskette packages and often on the diskettes. They refer to the number and type of magnetic recording surfaces. SS/DD - Single-Sided, Double Density, 5.25" disks, 160 Kilobytes rarely used, not sold in stores anymore. DS/DD - Double-Sided, Double Density, 5.25" disks, 360 Kilobytes 3.5" disks, 720 Kilobytes DS/HD - Double-Sided, High Density, 5.25" disks, 1.2 Megabytes 3.5" disks, 1.44 Megabytes The double density recording technique is now standard. The high density diskettes require high density drives, which can read at both the standard and the high density. For example, the high density 3.5" drives can read and write double density diskettes. H The ST506 was pioneered by Seagate Technology with the 5-megabyte hard disk drive. It was derived from two other interfaces: the SA1000 for 8-inch drives and the SA450 for 5.25" floppy disk drives. The ST506 interface requires that the read-write head be stepped or moved across the disk one track at a time by carefully timed pulses. Since these pulses actually cause the read-write head's stepper motor to advance a notch, they cannot proceed faster than the disk drive can move the head. The ST412 interface introduced an enhancement that eliminated this problem, the buffered seek. Instead of requiring the controller to slow the pulse rate to whatever the mechanism could handle, the ST412 simply counts the pulses as they come in. It then decides how fast to step the head to move the required number of tracks. xA stack is a set of hardware registers or a reserved amount of main memory that is used for arithmetic calculations or for keeping track of internal operations. Stacks are used to keep track of the sequence of routines that are called in a program. The operating system and a program can maintain one or more separate stacks. Stacks normally work on a Last-In-First-Out (LIFO) basis. The last item, or address, placed or pushed onto the stack is the first item removed or popped from the stack. A stack pointer is a register or address that identifies the location of the most recent item placed on the stack. ¾nA stationary form of electricity, static electricity is produced whenever positive and negative charges are separated by friction, pressure, heat, or induction. The separation produces a voltage, and when the voltage exceeds the insulating potential of the medium separating the oppositely charged particles, a discharge occurs as the particles rapidly come together. Static electricity can be easily built up on your body as you walk across a carpeted room. When you touch the metal case of your microcomputer, the charged particles are attracted to the charge "sink" provided by the grounded metal case. Fortunately, no damage is likely to occur to the sensitive components. However, if you are working with unprotected components such as memory boards, memory chips, math co-processors, or any printed circuit boards, the static electricity that may build up on your body could definitely damage or zap these sensitive components. µ=Also called page-mode RAM, static-column RAM is a memory design whereby system RAM is divided into equally sized areas, called pages, using column addresses. Static-column RAM requires a special static RAM chip (SRAM) which is more expensive and harder to find than ordinary DRAM. On 386-based computers that use memory paging, each bank of RAM (usually 1MB or 4MB in length) is logically divided into rows and columns. kStopbits is a data communications term used to distinguish where one character stops and another starts in the process of a serial data transfer. Data communication programs normally add one, or sometimes two stopbits on the end of each character. The term databits refers to the number of bits used to define a character during serial data transmissions, usually 7 or 8. When connecting two computers together via the communications ports, it is necessary to set the same number of stopbits and databits at each end. For example, during the setup process for a communications program the number of stopbits and databits need to be specified for each different BBS or On-Line Service. For most BBSs, the stopbits parameter is set to one and the databits parameter is set to 8. ƒ[Streaming tape is magnetic tape that is sometimes used to backup data stored on hard disks. The name streaming tape derives from the fact that such systems often operate in a continuously running, or streaming mode, with data stored or retrieved while the tape is running. Quarter inch tape cartridges are often used with personal computer streaming tape backup systems. UwStructured programming is a discipline in which each sequence of program instructions performing a specified logical procedure is viewed as a separate unit with one entry and exit point, so that the program can be followed as a series of processing steps and be easier to understand. Good structured programming practices lead to reduced cost in program modification and maintenance as well as in the original development. Technical conferences or reviews intended to analyze program design, detect errors, and exchange knowledge and ideas are called structured walk-throughs. ÁmA subdirectory is an area on a disk for storing files. Subdirectories consist of files and/or other subdirectories. A directory listing will show the names of files and subdirectories subordinate to that subdirectory along with file sizes, creation dates and times. Each formatted disk contains a main directory also called the root directory. With DOS, the most common hard disk root directory is referred to as "C:\" or just "C:". QA subroutine is a group of program instructions that stand-alone and perform a specific processing function. Subroutines are called from main programs or from other subroutines. The major reason for using subroutines is that they are coded and debugged once but may be called and executed from many different points in a program. Subprograms, functions, macros, procedures, and program modules are all subroutines. A good example of a subroutine is a group of program instructions to calculate the square root of a number and return the answer to the calling program. [BAs a standard introduced by IBM in 1987, the VGA, Video Graphics Array provides for a screen resolution of 640 x 480 pixels. Super VGA, introduced a year later offers a resolution of 800 x 600. And then, along came super-extended VGA, or 1K-resolution VGA, at 1024 x 768 pixel resolution. See the Table "Video Display Standards" xrA surge protector or surge suppressor is an electrical device that is placed between sensitive electronic equipment and the source of the electrical energy, usually a wall socket. This inexpensive device protects the electronic equipment from an over-supply of voltage on the incoming lines of the power company. Lightning is a common source of power surges or spikes. What happens when a voltage spike comes down the line ? If the spike is strong enough, the protective circuitry in the surge protector blows and prevents any further electrical power from reaching the sensitive equipment. For continued protection, another surge protector must be installed. A surge protector is not designed to protect from decreased voltages caused by brownouts. Protection from both high and low levels of voltages can be provided by a power line filter or voltage regulator. Ú[The term synchronous is used to designate events occurring at timed intervals regulated by pulses from the computer clock. A synchronous transmission is a communications mode in which a clock signal is transmitted with the data at precisely defined time intervals, to maintain the receiver and transmitter in synchronization. In synchronous transmissions, since events take place at fixed times, the completion of preceding events need not be acknowledged. fEvery computer programming language has rules about how its commands and instructions should be written and in what order. These rules make-up its syntax. The syntax of a programming language is checked by that language's compiler at compilation time. ± The term SysOp stands for System Operator and, in the world of microcomputing, refers to the person responsible for maintaining a Bulletin Board System (BBS). The job responsibilities of a SysOp can be quite involved. On some BBS's, the SysOp acts not only as an administrator, file manager, and librarian, but also as a mediator for the various electronic meetings or conferences that may be taking place on the BBS. )T-1 is an AT&T term that describes a communications circuit or a data-carrier facility which consists of a cable and its hardware. T-1 is a service provided by long distance communications carriers for the transmission of digital signals whether voice, video, or data. A T-1 carrier can transmit large volumes of information across great distances at high speeds and at a lower cost than traditional analog leased-line services. A full T-1 line is a 4-wire circuit (two pairs of normal twisted wires) providing 24 separate 64 Kbps logical channels. The total capacity of a single T-1 line is the sum of its 24 subchannels, plus 8 Kbps overhead, for a total of 1.544 megabits per second. T-1 is a standard for digital transmissions in North America and is not compatible with T-1 in Europe. ï:Copies of data and program files are called backups. Most backup systems fit into one of two categories; tape or disk. With microcomputers, tape backups can be performed on systems with hard disk drives and an internal or external tape backup drive. Most tape drives for microcomputers use a magnetic tape cassette or cartridge. There are generally two types of tape backups, image and file-by-file. An image backup operation creates one dataset on the magnetic tape, containing all the information that was on the disk drive. A file-by-file backup allows the operator to select certain files and/or subdirectories from the disk to be backed-up. Not all backup programs allow individual files to be restored from image backups. Ú}TCP/IP is short for Transmission Control Protocol/Internet Protocol. It defines certain network rules developed by the U.S. Department of Defense. Actually, both TCP and IP are protocols contained within the larger set of Defense Data Network protocols. It is an implementation of two layers of the OSI Model. TCP breaks data transmissions up into packets, reassembles them at the other end in the correct order, and re-sends portions that do not transmit correctly. IP, the internet protocol, is responsible for the actual routing and transmission of the data. TCP/IP provides networked users with the following services: File transfer, remote login, E-Mail, remote job execution, and server functions. kOOne TB equals 1MB times 1MB. (2 to the 40th power) or 1,099,511,627,776 bytes. 'Tera' is a binary analog to the decimal 'trillion'. The 80386 microprocessor can access 64 TB of virtual memory. Terabytes are used to measure the storage capacities of optical disks, mass data storage devices. See the Conversion Table "Bytes to Terabytes" WA terminal is a device used by a person to send data to and receive data from a computer system. It consists of a keyboard and a CRT and/or printer and can be located at great distances from the computer, connected by any of various communication lines. A terminal differs from that of a personal computer's monitor or video display. A personal computer together with its video components, however, has the potential to serve as a terminal for another computer. This process is called terminal emulation. PIn addition to computers, mainframe and minicomputer manufacturers also produce a wide variety of peripheral devices. The terminal is one such device. It is used for data input and output and normally has a keyboard for input and a video screen for output. Oftentimes these computer systems or certain programs will only communicate through a particular type of terminal design. The data sent to and from the computer must conform to a defined format specification. Terminals are designed and built to satisfy that requirement. Software programs for microcomputers have been written to satisfy that requirement such that the host computer system communicates with the microcomputer as if it were a dumb terminal. This process is called terminal emulation.   Generally speaking, microcomputers operate in one of two modes, either text mode or graphics mode. In text mode, also referred to as alphanumeric or character mode, no graphical images can be displayed. The characters are taken from the ASCII character set. The IBM PC and compatible computers, can operate in either one mode or the other. In the early to mid 1980's, most PCs were operated in text mode. By the late 1980's, the hardware and software had improved to the point that operating in a graphics mode was acceptable. As more and more applications are developed to operate in the graphics mode, the text mode will become a thing of the past. ‹tA computer of the third generation is classified as beginning in the mid 1960's and continuing into the early 1970's, characterized by physically smaller computers using integrated circuits on chips for most of its circuitry, while utilizing disk storage and on-line terminals. The third generation of computers started roughly in 1964 with the advent of the IBM System/360 series. PTIFF is an acronym for Tagged Image File Format. TIFF provides a way of storing and exchanging digital image data. Aldus Corp., Microsoft Corp., and major scanner vendors developed TIFF to help link scanned images with the popular desktop publishing applications. It is now used for many different types of software applications ranging from medical imagery to fax modem data transfers, CAD programs, and 3D graphic packages. The current TIFF specification supports three main types of image data: black and white data, halftones or dithered data, and grayscale data. ø[Time slicing is a scheduling method whereby a particular task is given control of the microprocessor in a multitasking environment. A program executes during its given time slice and is then swapped out to await its turn to resume execution. $The term token-passing is used to define an access scheme, which is contention free, in a network of computers. A token, or the right to broadcast signal, is passed through every workstation on the network, whether it needs to transmit data or not. This gives each station an equivalent share of the network time. A workstation can only transmit a message when it has the token, but the cable is always clear when the messages are ready to be transmitted. Token-ring and ARCnet technologies use a token-passing access scheme. }MIntroduced by IBM in October of 1985, Token-ring refers to the wire and the access protocol scheme whereby the workstations of a network relay packets of data called a token around in a logical ring configuration. When a station wants to transmit, it takes possession of the token, transmits its data, then frees the token after the data has made a complete circuit of the electrical ring. This architecture is described completely in the IEEE 802.5 set of standards, which defines the cabling, electrical and physical topology, and access scheme of network products. IBM's Token-ring system continues to support an increasing number of mainframe computer Token-ring interfaces so that microcomputers can share data on the mainframe networks. It connects microcomputers via a special cable containing twisted wire pairs and transmits data at four megabits per second. ýRThe term topology can refer to either the physical or the logical configuration of a local area network (LAN). Physical topologies, such as ring, star, and bus, are always associated with the layout of the workstations and the cabling that connects them. The logical topology describes the way in which the flow of data is regulated to and from the workstations on the network. ARCnet, Ethernet, and Token-ring are the most common logical topologies offered for today's local area networks. YmThe components that make-up a microcomputer, such as the disk drives, the power supply, the motherboard, and the various other controller cards are most often housed in a cabinet that is designed to rest in a horizontal position on a desktop or table top. In order to conserve valuable desktop space, some microcomputers are housed in a tower case that is designed to stand upright on the floor. Although the tower case is more practical, and often provides more space for half-height drives, they are not as popular as the conventional cases, and are consequently more expensive. AA track is a storage channel on a disk, tape, or CD-ROM. With magnetic devices, data bits are recorded in tracks as reversals of polarity on the magnetic surface. On floppy disks and hard disks, tracks are concentric circles of data. Each track is a magnetic ring slightly wider than the read/write head in the disk drive. A 360 K floppy disk has 40 tracks. Each track has a number of sectors. Tracks are defined and recorded on a disk by the operating system during a disk format operation. With magnetic tapes, tracks are parallel lines. The track format is determined by the specific tape drive, either 7-track or 9-track. With CD-ROMs, data bits are recorded in tracks, not magnetically but as physical pits underneath a clear, protective layer. þeA trackball is an input device for moving the cursor around on a video display screen. It consists of a mounting, usually a small desktop box, with a ball inset. As the operator spins the ball with his fingers, or the palm of his hand, the cursor on the screen moves at the speed and in the direction of the ball's motion. Trackballs are used in various graphics applications as well as arcade games. Unlike a mouse, a trackball doesn't run out of desk space or need to be repositioned. ï]There are basically three methods for feeding paper into a printer. A single sheet of paper can be fed into the printer in a manner similar to a typewriter whereby the paper is pinched between the platen and a roller. Some printers, like the new laser printers, use sheet feeders, trays filled with single sheets of paper which are fed into the printer as needed. Other printers use tractor feed mechanisms with a pair of pin-studded belts or wheels that rotate in unison and pull the paper, which is punched with holes along the margins, into the printer. Tractor feed printers are fed boxes of continuous paper, fan-folded at the perforations so that individual sheets can be separated after the printing task is complete. The TRON project is a standardization effort that aims to establish a set of common data-interchange standards that will make it easy for all computers to communicate in real time. TRON encompasses all computers, including those found in household appliances, cars, calculators, marine navigation, stereo systems, etc. TRON is an acronym for The Real-Time Operating System Nucleus. The name TRON applies to the development of a whole concept, not to a specific product. TRON encompasses the development of an open architecture, a family of VLSI chips, and system software. All TRON specifications are available for adoption by anyone, free of charge. This standardization is coordinated by the non-profit TRON Association, in cooperation with the University of Tokyo. 2rTSR is an acronym for Terminate and Stay Resident. With microcomputers operating under DOS, only one program can be executing at a time. Normally, when a program is terminated, the memory is freed for the next program. But computer programs can be designed and written to remain in memory until explicitly removed or until the power is shut-off. These TSR programs, because they remain in memory, can be re-activated by a pre-defined keystroke sequence while another program is active. Unfortunately, the use of TSRs often results in conflicts between the programs. Some programs will not even load properly if a TSR is resident in memory. An example of a useful TSR is a program that provides an on-screen calculator that can be activated while using a word processor or a spreadsheet program. ÍOTTL is an acronym for Transistor to Transistor Logic. A TTL display is a monitor that accepts digital input at standardized signal voltage levels. Digital signals are also called TTL signals. ,Twinaxial cable, often abbreviated twinax, is similar to coaxial cable but with two inner conductors instead of one. It is actually two coaxial cables in a single insulated jacket. Twinaxial cables are used with the IBM System 34/36/38 and AS400 communications environments. DWhen two small insulated copper wires are wrapped or twisted around each other to minimize interference from other wires in the cable, the result is referred to as twisted pair wiring. There are two types of twisted pair cables: unshielded and shielded. Unshielded twisted pair wiring is commonly used in telephone cables and provides little or no protection against interference. Shielded twisted pair wiring is used in some networks for connecting workstations but the signals must be boosted periodically. Although it has limited bandwidths compared to coaxial cable or optical fiber, inexpensive shielded twisted pair cabling is used by AT&T in its StarLAN network and it can be used as an alternative to coaxial cable for Ethernet networks. ÑyThe term two's complement refers to a number in the binary system (base-2 system) that is the true complement of another number, commonly used to represent negative numbers in computing. The two's complement is a method for representing integers and is defined in the IEEE-754-1985 specification. A two's complement of an integer can be derived by reversing the digits in a binary number (change 1's to 0's and 0's to 1's) and adding one to the result. 61A typeface is the design of a particular set of letters, symbols, numbers, and punctuation marks. For example, Helvetica, Times, Palatino, and Optima are typeface families. Each family can have a number of different typefaces such as Times Roman, Times Bold, Times Italic, which share the same underlying characteristics, but require a separate design for each weight or slant. A font is a complete assortment of print characters for a single typeface in a single size. For example, 12-point Helvetica is a different font than 10-point Helvetica. ÚzAcronyms: UART, Universal Asynchronous Receiver/Transmitter USRT, Universal Synchronous Receiver/Transmitter USART, Universal Synchronous Asynchronous Receiver/Transmitter These are integrated circuits (chips) with serial/parallel conversion, parallel/serial conversion, and other facilities designed for use in synchronous and asynchronous serial communications. These devices can take data directly from, or place it directly on the data bus. Å(Both of these terms refer to areas in random access memory above 640K and below 1 MB on microcomputers using Intel 80386 CPUs and later. The UMA, Upper Memory Area, refers to the expanse of memory between 640K and 1 MB and is normally reserved for hardware use. The ROM BIOS is located in the UMA as well as the ROMs of various adapters in the system such as the video card and the hard disk controller. Expanded memory boards locate their page frames in the UMA. The UMBs, Upper Memory Blocks, are pockets of usable RAM created in unused areas of the UMA. The primary use for UMBs is to store TSRs and device drivers above 640K therefore making more RAM available for application programs. |In 1987 work began on a new computer code called Unicode which assigns a number to every printed character in use today. Joe Becker of the Xerox Palo Alto Research Center coined the name Unicode for "unique, universal, and uniform character encoding." Unicode's fixed 16-bit (2-byte) code allows 65,536 characters to accommodate all major living languages, including ideographs used in Japan, China, Taiwan, and Korea; Cyrillic; Hebrew; Arabic; Greek; Sanskrit; and many others. It also has math and technical symbols, subscripts and superscripts, accent marks, control codes, and code that mark the direction of the text. ASCII, the code in use today, has always lacked the characters to express the written words of most of the world's peoples. Before the turn of the century, major computer companies will actually implement Unicode in their systems and software. 0WUNIX is an operating system developed by AT&T at Bell Laboratories by a team of programmers lead by Ken Thompson and Dennis M. Ritchie. Since the UNIX operating system is easy to use, its design concept had a great influence on other operating systems for microcomputers. UNIX is widely used on a variety of computers, from mainframes to micros. It is a powerful multitasking, multiuser system with many high-level utility programs. Because of its superior capabilities as a program development system, UNIX is expected to grow in popularity. 'The Universal Product Code is a ten-digit computer readable bar code used in labeling retail products. The code in the form of vertical bars includes a 5-digit manufacturer identification number and a 5-digit product code number. Related information, such as pricing and inventory control, is then stored in the computer so that when the product code is passed over a scanner and read into the computer, product prices can be easily transferred and inventory data accurately updated. A sample of a Bar code: º³Ûººº³Û³Ûºº³Û³º³ºº³Û³ º³Ûººº³Û³Ûºº³Û³º³ºº³Û³ º³Ûººº³Û³Ûºº³Û³º³ºº³Û³ º³Ûººº³Û³Ûºº³Û³º³ºº³Û³ º³Ûººº³Û³Ûºº³Û³º³ºº³Û³ + A battery operated device that supplies a computer system with electricity in the event of a power failure or an unacceptable voltage level, is called an Uninterruptible Power Supply. A true UPS system always supplies power through a battery even when commercial power is available. There is no switching back and forth between battery and commercial power. Sophisticated UPS systems are tied to electrical generators that are designed to provide electrical power for days. Small UPS systems or stand-by power supplies switch to battery backup power for a limited time so that the computer can be powered down in an orderly manner. One of the key factors to consider before purchasing a stand-by power supply system is the amount of time required to switch to the battery backup power. ‘When a new version of a computer or software system, such as a language processor, produces identical results for a program executed on the previous version, the new version is said to be upward compatible. New releases of software or upgrades to peripheral devices that can do everything that the previous model could do, plus some additional functions are said to be upward compatible. ~When a program is easy to understand by a wide variety of people, the end users, not just the programmers, it is said to be user- friendly. A user-friendly program is one that is not intimidating to those who are unfamiliar with computers, or the program itself. R-As a type of freely-distributed software, user-supported software is copyrighted by the author and is thereby protected by U.S. and international copyright law. It may be freely copied and passed on to others, but each user is expected to register with the author and pay a usage fee. The fee may include some or all of the following: printed documentation, the latest version of the program on disk, telephone support, free updates, and commissions, but most importantly a legal license to continue using the software. User-supported software is distributed as Shareware. ¬7Unshielded Twisted Pair cabling is the wire that is often used indoors to connect the telephones to outside service. It comes with two or four wires twisted inside a flexible plastic sheath or conduit. It utilizes modular plugs and phone jacks, which makes it easy to relocate the phones, modems, workstations, or other devices. Unshielded Twisted Pair (UTP) is an excellent choice of cable for a network installation because there are adapters for easy conversion to all other types of cabling and because UTP is used for the transmission of both voice and data. ISO 8877, RJ-45 connectors are used with UTP. UTP is also referred to as D-Inside Wire (DIW). ü'A Value Added Reseller is a company or organization whose products result from the addition of some valuable feature to another vendor's product, a very common practice worldwide. VAR is also used as an abbreviation for Value Added Resource. 0The Vertical Blanking Interval is the portion of the television signal which carries no visual information and appears as a horizontal black bar between the pictures when a TV set requires vertical tuning. The VBI is used for other applications, such as carrying close- captioned signals for the hearing impaired. Digitized data can also be inserted into the VBI for transmission at rates in excess of 100,000 bits per second. Information services such as stock market quotations and news offerings are now available via the VBI of a cable television signal. The data embedded in the VBI signal is retrieved from a standard cable or satellite receiver wall outlet by a receiver set, which connects to a RS-232 port on a microcomputer. Software packages then allow subscribers instant access to the information, which may be displayed in a number of user-definable formats. âZVESA is an abbreviation for Video Electronics Standards Association. Along with eight leading video board manufacturers, NEC Home Electronics founded VESA in the late 1980's. The association's main goal is to standardize the electrical, timing, and programming issues surrounding 800 by 600 resolution video displays, commonly known as Super VGA. This standard provides guidelines for video board makers on how best to achieve the resolution of 800 by 600 pixels. ÇWithin a year after IBM announced its PS/2 Display Adapter in 1987, many third-party VGA boards became available offering increased performance and added features such as 16-bit capability, enhanced resolutions, software and speed-up utilities, and hardware panning and zooming capabilities. These VGA boards fall into one of three categories: BIOS-compatible, while supporting all the VGA modes; many with higher resolutions, with the limited BIOS compatibility, problems may arise with software written directly to the VGA hardware registers. Register-compatible, in addition to being BIOS compatible, these boards are also compatible with the IBM VGA hardware registers and should have no problems with software (such as Windows 386 or OS/2). Enhanced VGA boards, by third-party vendors go one step beyond VGA. In addition to being VGA compatible at both the BIOS and register level, these VGA boards offer more colors at higher resolutions. MThe VGA is an analog video controller. It handles color in much the same way as a TV receiver. The VGA produces a signal that can vary in small increments over a large spectrum of colors. The VGA requires an analog color monitor. Video Graphics Array refers to the display adapter built into IBM's Personal System/2 Models 50, 60, 70, and 80. This adapter can only be used with one of IBM's analog monitors. The VGA provides a text mode with a 9-by-16 dot box for characters, it emulates the EGA modes and the two new graphics modes of MCGA, and it provides its own graphics mode with 16 colors and 640-by-480 pixel resolution. For more information on video standards, ESCape from here, hit Function Key F5 for Tables Menu and select Video Display Standards. 95In the past, many researchers and industry watchers have predicted that one or another video display technology would finally dominate and eliminate the competition. However this has not happened. Video displays are used not only with computers, but with any device that needs to display text or graphics like televisions, household appliances, medical, and military equipment. By far the oldest and most popular display device is the Cathode Ray Tube (CRT), which first appeared in the early 1900's. The other three major display technologies are the Liquid Crystal Display (LCD), the gas-plasma display, and the electroluminescent (EL) display. Minor display technologies, comparatively, are the Vacuum Fluorescent Display (VFD), electrophoretic displays, and the Light Emitting Diode (LEDs) displays. » A virtual disk is an area of memory that has been defined for temporary storage of programs and/or data. A device driver is used to set-up and access the data in this area in a manner similar to a hard disk but much faster. A virtual disk is also referred to as a RAM disk or RAM drive because it is created in Random Access Memory. If your computer has extended memory (above 1 megabyte), or if it has an extended memory board that meets EMS, you can use this area for one or more virtual disks. Otherwise, a virtual disk can be built in conventional memory. When the system is re-booted, or when the power is turned off, the information stored in virtual disks is lost. ¤$When a program requires more space than is available in main memory, a direct access storage device can be used to hold program segments until needed in memory. The program utilizing virtual storage appears to be held entirely in memory. The virtual memory system allows a program to be broken up into segments, called pages. Instead of bringing the entire program into memory, it brings in as many pages that will fit and leaves the remaining pages on disk. When instructions are called for that are not in memory, the appropriate disk page is read in, overlaying a page in memory. The input and output of program pages is called paging or swapping. /Voice mail consists of messages spoken into a telephone, converted to digital data, and stored in a computer system. The messages can be stored either in RAM or on a hard disk for later retrieval. Voice mail is a general term that includes both answering machine and in-house voice mail systems. Sometimes referred to as phone mail or voice processing systems, voice mail systems accept commands from a touch-tone telephone. In addition to the primary function of answering the telephone and taking a message, PC-based voice mail systems can provide a variety of other related features, such as providing dictation services, auto-dialing for voice calls, voice synthesis, responding to alarm signals by dialing an emergency number, and providing inbound and outbound telemarketing services. TLComputer memory, made up of dynamic RAM or static RAM chips, is called volatile memory because its contents are lost when the power is shut down. Non-volatile memory, also called firmware, is capable of retaining its contents without power. Examples of non-volatile memory chips: ROM's, PROM's, EPROM's, and EEPROM's lMost modern day computers, including microcomputers, minicomputers, and mainframes are designed according to the 'Von Neuman architecture'. The concept is named after Hungarian-born John Von Neumann (1903-1957), an internationally renowned mathematician, who introduced the idea in the 1940s. The term 'Von Neuman architecture' refers to the sequential nature of our modern day computers whereby instructions are stored and acted upon one after the other. It refers to the conventional computer design, composed of the five key components; a central arithmetic logic unit, a memory connected by a bus to a central processing unit that performs operations sequentially, and input and output devices. Today, the operational slowdown caused by funneling information into a single channel between the CPU and memory is referred to as the Von Neuman bottleneck. Ø7Video Random Access Memory chips are modified DRAM's on video boards to allow them to transfer a large number of bits from the memory array to a separate internal serial-shift register. After making the transfer, the contents of the shift register are independently shifted out to the video display. The original VRAM was 64k-bit in size. It was followed by the 256K-bit device that combined the functionality of four 64K-bit VRAM's on a single chip. The latest VRAM generation is a 1-megabit device organized as 256K-by-4-bit with four 512-bit shift registers. With the increasing resolutions of graphics displays and denser memory devices, the VRAM is becoming indispensable to frame-buffer design. €uA wait state is a phase during the execution of a program in which the processor must wait one or more clock cycles until memory is able to respond to the processor's request. A wait state is a pausing cycle in CPU operation that lets the microprocessor synchronize with slower memory. "Zero Wait State" - no waiting If memory is slower than the processor, the system is said to be bus bound. If the processor is slower than memory, the system is processor bound. The ideal memory system is one in which the rate that memory can supply data to the processor matches the rate that the processor can execute code. þQWhen two or more computers are linked together for the purpose of sharing information and/or peripheral devices, a network is created. When the network is not confined to a geographically restricted area, such as within the same building or perhaps on a college campus, it is referred to as a Wide Area Network. Typically, wide area networks serve to interconnect Local Area Networks in different cities, states, and countries. A global communications network of computers is referred to as a WAN. WANs use several means of data transmission, including modems. Dedicated digital transmission lines are popular for data that must be transmitted quickly. Public data-transmission services, such as packet switching networks are also widely used. ÑQA computer's operating system is initiated with a boot procedure, a start-up from scratch. It is not always necessary to turn-off the power and then re-apply it to start the boot procedure. If your IBM-compatible computer hasn't locked-up, and the keyboard is active, the system can be warm booted by depressing the following three keys simultaneously: Ctrl-Alt-Del When your system is warm booted, the contents of memory are not actually erased. The operating system is simply reloaded, and the pointers to the beginning of available memory are reset. In fact, a DOS program called DEBUG can be used to read from the part of memory that was in use prior to the warm boot. ü/The performance of a computer system is often evaluated by measuring its operational speed in a variety of different tasks. The Whetstone benchmark program, developed in 1976, was designed to simulate arithmetic intensive programs used in scientific computing. It is applicable in CAD and other engineering areas where floating- point and trigonometric calculations are heavily used. The Whetstone program remains completely CPU-bound and performs no I/O or system calls. The program was originally written in ALGOL, although the C and Pascal versions became more popular by the late 1980's. The speed at which a system performs floating point operations is measured in units of Whetstones or floating point operations per second (flops). ?With DOS and OS/2, there are two characters, * and ?, that can be used when specifying one or more filenames in an operation. These characters are called wildcards. A 'grep' search also uses wildcards. For example, the DOS command DIR *.COM will cause a directory listing of all the files that have the extension .COM to be displayed on the screen. The asterisk (*) character can represent any valid set of up to eight characters. The question mark (?) can represent any single character in a filename. For example, the DOS directory command, DIR SEPT??.DAT would show directory information on the following filenames. SEPT02.DAT (and any other files with names starting with SEPT, SEPTEM.DAT followed by two characters, and a .DAT extension) Œ0A Winchester disk is a hard disk storage device developed by IBM. Winchester disks are characterized by their non-removable, sealed platters; narrow tracks; and a lubricated surface on which the read/write heads rest during start and stop operations. During normal operation, the read/write heads float above the surface of the platters on an air cushion. The Winchester disk was originally designed with a dual 30 megabyte capacity, and its 30-30 specification, the same as a Winchester rifle, accounts for its name. Although originally a self-contained, removable unit, the term is often used to refer to any fixed hard disk. s=The modern computer usage of the term "window" refers to a section, frame, or partition of a larger entity. With expanded memory on personal computers, windows are defined in main memory for swapping data in and out. When your video screen is divided into sections to display related information or messages, each section is referred to as a window. There are fundamentally two kinds of windowing schemes for the display screen: "tiled windowing" and "overlapping windowing". In a tiled windowing system, the multitasking operating system does not allow the windows to overlap. Each active task is only allocated a rectangular screen area in which to display messages. In the overlapping scheme, the windows are like pieces of paper of varying sizes laid on top of each other. The user can move the windows about on the screen to see what was under them. |Microsoft Windows is a multitasking Graphical User Interface (GUI) environment that runs on DOS-based microcomputers. It provides a standard interface based on drop-down menus, screen windows, and a pointing device such as a mouse. In order for a program to be able to run in the Windows environment, it must be specifically designed to take advantage of these features. ¨Wire wrap is a process whereby electrical connections can be made without the need for soldering. A specially designed tool wraps the wire tightly around a square post. The sharp edges bite into the wire, producing a reliable connection. Large circuit boards containing thousands of connections can be wire wrapped in a matter of seconds with programmable numerically- controlled special purpose machines. ­NWNIM is an acronym for Wide Area Network Interface Module. It is a printed circuit board designed to provide up to four asynchronous communication ports to a network of computers. The WNIM can reside in a workstation or as an internal bridge in a file server. Along with an asynchronous communications software package, WNIM boards provide both incoming and outgoing telephone calls for LAN- to-LAN data transfer. ØEA computer word is a storage unit of information, consisting of a number of bits that comprise one storage location in main memory. Large computers may have 32, 36, 48, or 64 bits in each word. Often microcomputers, personal computers, will have 16-bit words. When speaking of an IBM PC or compatible, 'word' can refer to 16 bits or 8 bits, depending on whether the point of reference is the computer's 8-bit data bus or its 16-bit internal processing. bJOne of the most popular uses for personal computers is word processing. It is an information processing system that relies on automated and computerized typing, copying, filing, dictation, and document storage and retrieval. A word processor is a computer program designed to provide easy manipulation of text. It can be used to write letters and/or documents, while inserting, deleting, and/or changing words, paragraphs, or pages. Examples of popular word processors for microcomputers: WordPerfect WordStar MultiMate PC-Write Microsoft Word IBM DisplayWrite Ú_Word wrap is a word processor feature. While typing, if there isn't enough space for a word at the end of a line, as the operator continues to type, the whole word is moved to the beginning of the next line. )CA worksheet is a data file created and processed by a spreadsheet program. The popular spreadsheet program 1-2-3 from Lotus Development Corp. uses the term worksheet to refer to the data file that is created, edited, and saved during a session of data processing. Many variations of the filename extension are in use today to help identify these files. Some of the most popular are .WK1, .WK2, .WKS, .WKQ. For example, if you are using the spreadsheet program QUATTRO to create a data file, the output filename may be MYDATA.WKQ. ².A workstation is a terminal or a microcomputer from which an operator can gain access to a network. The nodes of a local area network are called workstations and can be the diskless type or the high-performance stand-alone microcomputers. Shortly after the introduction of microcomputers, the term workstation mostly referred to the more powerful engineering systems capable of state-of-the-art graphics for CAD/CAM. µA worm is a nasty type of computer program designed to reproduce itself over and over. Each new copy of the program creates another copy. The purpose of a worm program is to cause a computer system to crash by reducing the available disk storage space to zero. A worm program is most often targeted for local area networks or large multiprocessing systems. This type of destructive program is not considered a software virus because it has no damaging effect on other programs or data files. Probably the most well-known worm program was activated on the large Internet network on November 2, 1988. In two days, an estimated 6200 UNIX based computer systems were infected. DKWORM is an acronym for Write Once Read Many, or Mostly. It is an optical mass storage device capable of storing many megabytes of information, but can be written to only once on any given area of the disk. A WORM disk typically holds more than 100 Megabytes of data. Because a WORM drive cannot write over an old version of a file, new copies of files are made and stored on other parts of the disk whenever a file is revised. WORM disks are used to store information that does not change often, such as system files, compilers, and many application programs. ~Hard disk drives for microcomputers are manufactured by numerous companies resulting in a wide variety of designs, data access rates, and storage capacities. But, generally speaking, hard disk drives consist of at least three read/write heads for transferring data to and from the magnetic surfaces, called platters. Cylinders are imaginary vertical columns of tracks on the disk platters. The tracks on the inside of the circular platters are shorter in length than those closer to the edge. The write precompensation number of a particular hard disk drive is specified by the manufacturer. It is the cylinder number at which the read/write heads increase the level of electrical current to compensate for losses in the inner tracks of the platter. Flux transitions are more widely spaced on the longer tracks at the outside of the circular platter and need no additional compensation. §A write-protect feature prevents a disk or tape from being written to thereby protecting any existing data. With floppy diskettes, there is a write-protect notch in the jacket that prevents writing to the diskette when the notch is covered with a gummed tab or label. On the 3.5" microdiskettes, the write-protect notch is a square hole punched through the shell with a slug of plastic built into the shell that can be slid over or away from the hole. When the notch or hole is closed, new data can be written to the diskette. With magnetic tapes, a plastic write-protect ring is inserted in the back of the tape reel to prevent writing data to the tape. :yAn acronym for What You See Is What You Get. The term WYSIWYG, pronounced "wizzy-wig", is used as an adjective to refer to computer programs such as word processors that generate screen images that are identical in position and type appearance to the final document, as opposed to those that show the formatting or special type requested only when the document is printed. The advantages are twofold: the planning of a visually pleasing final document is easier and errors in the printed document can be found quicker when the document is on the screen. àKX.25 is a CCITT standard communications protocol used internationally in packet switching networks, originally defined in 1976. It has been revised and updated every four years since. Rather than sending a stream of bits like a modem, an X.25 router sends packets of data. There are varying packet sizes and types. Each packet contains data to be transmitted as well as information about the packet's origin, destination, size, and its place in the order of the packets sent. There are clear packets which perform the equivalent of hanging-up the phone. There are reset, restart, and diagnostic packets. On the receiving end, the packet assembler/ disassembler (PAD) in the router translates the packets back into a readable format. Your credit is often verified at the check-out counter by a credit card reader that dials an X.25 network port to send your credit card number, store ID, and the purchase amount, assembled into packets to the proper bank for verification. ;X.400 is a term that refers to a series of OSI and CCITT standards that describe the details of encoding electronic mail messages, both textual and graphic, for transmission between unlike computers and networks. X.400 is actually a subset of the CCITT X.25 standard which governs data communication on the packet switching networks. Both of these important standards are maintained so that information can be transmitted between all types of computers and a wide variety of specialized terminal equipment from many manufacturers. jxBase is a generic term used to represent the various database products on the market that are compatible with Ashton-Tate's dBase. xBase is a product category. The prime elements of xBase are the data model, the data file formats, and the applications development language. As Ashton-Tate's dBase, a data management system from the early 1980s, became an industry standard and grew in popularity, competitors such as Fox Software with FoxBASE and Nantucket with Clipper developed their products to be similar. The file formats are the same. The languages are referred to as being dBase compatible. 0XENIX is an operating system. It is a variation of UNIX written by Microsoft Corp. for use on IBM-compatible microcomputers. XENIX conforms to AT&T's System V Interface Definition (SVID) with additional enhancements such as file and record locking, graphics, and networking. XIntroduced by IBM in September of 1990, the EXtended Graphics Adapter is a 16-bit color video adapter with the capability of operating at a resolution of 1024 by 768 in a non-interlaced mode. The adapter offers support for 256 colors which results in 65,500 palettes at its 640 by 480 resolution. A 32,000 color display is interpreted by the human eye as true color. IBM hopes to establish XGA as an industry standard and has released the technical details to third-party developers thereby guaranteeing lower prices and wide availability. See the Table "Video Display Standards" OnXmodem is a file transfer protocol. It was the first file transfer protocol to come into widespread use in the microcomputer world. It was developed by veteran computer hacker Ward Christensen in the mid-1970's to transfer files between machines running the CP/M operating system. Until the late 1980's, because of its simplicity and public domain status, Xmodem remained the most widely used microcomputer file transfer protocol. The file to be transmitted is divided into 128-byte blocks. Each block is sent in sequence, together with a special starting character, an identifying number, and a checksum. The checksum is a number created by adding all of the bytes in the block together. 1K-Xmodem is an extension to Xmodem which increases the block size from 128 to 1,024 bytes, thereby increasing transmission speeds. )XMS, an abbreviation for Extended Memory Specification, is a software interface developed by Lotus, Intel, Microsoft, and AST Research. It defines a means of allowing real-mode applications to use extended memory and certain areas of conventional memory not managed by DOS. In order for the additional memory (RAM) to be utilized, an installable memory manager or device driver must be loaded and the application software must be designed to take advantage of it. A memory manager is part of the operating system or can be purchased separately. The most common are listed here. EMM386.SYS by Digital Research, with DR DOS HIMEM.SYS by Microsoft, with MS DOS QEMM386.SYS by Quarterdeck Office Systems, purchased separately 386MAX.SYS by Qualitas, purchased separately 7Acronyms for transmission on/transmission off, these terms are used to designate when the flow of data is stopped or started by a computer or computer device. XON and XOFF characters are used to control the flow of data between devices that operate at different speeds. The XON and XOFF characters are part of the ASCII code where XON is hex 11 and XOFF is hex 13. XON / XOFF is also known as DC1 / DC3. Consider a parallel printer. It can send special flow control characters to the computer as notification of status conditions. When the printer is able to accept data it will send an XON character. When it is unable to accept data, an XOFF character is sent. Other special characters can also be sent to notify the CPU of conditions such as paper-out or device off-line. Ò*XOR is an abbreviation for the exclusive OR Boolean operator. It is also sometimes abbreviated EOR. The XOR Boolean operation yields true if and only if one of its operands is true and the other is false. The XOR truth table is shown below where 0 represents a false condition and 1 represents a true condition. ÚÄÄÄÄÄÂÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄ¿ ³ a ³ b ³ a XOR b ³ ÃÄÄÄÄÄÅÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄ´ ³ 0 ³ 0 ³ 0 ³ ³ 0 ³ 1 ³ 1 ³ ³ 1 ³ 0 ³ 1 ³ ³ 1 ³ 1 ³ 0 ³ ÀÄÄÄÄÄÁÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÙ ­vAs a file transfer protocol, the Ymodem protocol was first released as part of Chuck Forsberg's program YAM ("Yet Another Modem"). Ymodem is actually an extension to Xmodem, to overcome some of the limitations of Xmodem. Ymodem allows information pertaining to the transmitted file to be sent along with the data, such as filename and length. Ymodem also increases the size of the Xmodem block from 128 to 1,024 bytes and adds the capability to transmit "batches" of files. In fact, Ymodem is sometimes referred to as Xmodem-1K, and vice versa. YmodemG is a streaming protocol built around the philosophy that no news is good news. It sends the entire file before waiting for an acknowledgment. If the receiving side detects an error in mid- stream, it aborts the transfer. YmodemG is not an error correcting protocol; it is designed for use with high-speed modems, which have built-in error-correcting protocols. õeZAP is a programming command that operates on a database file. When the ZAP command is issued, all the records in the currently opened database files are permanently deleted, erased. The structure of the current file remains intact, only the records are removed. If there are index files or an associated memo file, all records in these files are also removed. In a network environment, the current database file must be opened in an exclusive mode before the ZAP command is issued. Outside of a database programming environment, the term zap is often used in place of the word delete. "The files were zapped yesterday." A hardware device, such as a memory chip, can be damaged or zapped by discharging static electricity through it. ú\Zero suppression is the replacement of leading zeros in a number with blanks so that when the number appears, the leading zeros are gone. The data becomes more readable, for example, 000099 would be displayed on the monitor or printed as 99. OtA Local Area Network utilizing the communication ports of the workstations (COM1, COM2, etc.) and RS-232 cabling is referred to as a zero-slot or RS-232 LAN. The term zero-slot derives from the fact that the LAN set-up does not depend on network interface cards, which take up an expansion slot in the PC workstation. These type of LANs allow for the transfer of files several hundred feet and to share expensive peripherals but will always perform slower than LANs with network interface cards. Examples of RS-232 LANs: EasyLAN, LANlink, IDEAshare, ManyLink bKA ZIP file is a type of compressed file created with a popular program called PKZIP.EXE written by PKware, Inc. In the microcomputer world, a ZIP file is one that has been compressed, squashed, squeezed, crunched, and/or packed with a file compression program in order to use less disk space and to reduce the transfer time when sending files between computers. Data Libraries store program and data files in compressed format and rename the files using the ".ZIP" filename extension. For further information write to: PKware, Inc., 9025 N. Deerwood Drive, Brown Deer, WI 53223 USA #As a file transfer protocol, the Zmodem protocol was commissioned by Telenet and placed in the public domain. Like Ymodem, it was also designed by Chuck Forsberg and was developed as an extension to Xmodem, to overcome some of the limitations of Xmodem. Zmodem implements many of the features of the Kermit protocol, as well as the capability to "step down" to the Xmodem or Ymodem protocols on demand. Among the key features of Zmodem are a 32-bit CRC offering a degree of error detection 100,000 times greater than Xmodem CRC, a server facility, batch transfers, and fast error recovery. Zmodem was also specifically engineered to avoid sending certain sequences, such as ESCape-carriage return-ESCape, that the Telenet network uses to control the connection. $LZone recording is a technique for increasing the storage capacity of magnetic disk drives. Conventional disk drives record the same amount of data on each track of the disk platter. However, the amount of surface area close to the center of the circular platter may be many times smaller than the areas at the outer edge of the platter. Thus the density of the data at the center is the highest on the drive. In theory, the same data density could be used on the entire platter. Zone recording accomplishes that by placing more data on each track as the heads move away from the center. The motor speed remains constant while the speed of reading and writing data is varied depending on the position of the heads. Near the edges data is transferred at considerably greater rates. ¿>Zulu time is a nickname for Greenwich Mean Time. Zulu time has nothing to do with the Zulu people living in Natal, South Africa. GMT, Greenwich Mean Time is the mean solar time of the meridian at a metropolitan borough of London called Greenwich, England. Greenwich Mean Time is used as the basis for standard time throughout most of the world. On the east coast of the United States, Eastern Standard Time is GMT minus five hours.