Modula-2 Introduction ~~~~~~~~~~~~~~~~~~~~~~~ In our first 2 issues of MEGADISC we have brought programs using True Basic and AmigaBasic. Our aim in these early releases of MEGADISC is to show readers some of the many different languages being used on the Amiga. As the Magazine develops we shall, if there is sufficient interest/demand, provide some form of tutorials on these programming languages. At the very least, we intend to pass on tips that should assist any of you that choose to do some programming. However, we require some feedback on the subject of programming languages. If readers have any experiences they think others would find helpful, they will be greatly appreciated. Participation is one of the aims of MEGADISC. We need to know what you would like to know! This time around we have some programs written in Modula-2, the langauge designed by Niklaus Wirth as a successor to Pascal, which he also created. In Modula-2, he has transformed Pascal into a language designed for systems programming as well as for general use. Professor Wirth first published details of Modula-2, a high-level language for programing a computer to perform concurrent real-time tasks, in December 1978. It was first implemented in 1979 on a Digital PDP-11 computer. By 1981 his research group at the Swiss Federal Institute of Technology (ETH), in Zurich, had produced working models of the Lilith microcomputer, whose operating system and utilities were programmed entirely in Modula-2. A British Standards Institute Working Party is now actively working on the development of a Standard for Modula-2. Recently Modula-2 has seen growing use in writing programs as components of embedded systems, ranging from word processors to space- craft control. Versions now exist for the Macintosh, Atari ST, Apple II, IBM compatibles, many Z-80 based micros and, of course, the Amiga. In fact, Modula-2 is fast replacing Pascal as the language of choice in teaching computer science. This is because it incorporates the good features of Pascal and more. Its expressive power also makes it suitable for higher level courses in programming, data structures and algorithms, which economize on learning effort for students. The popularity of a programming language depends largely on the availability of good, well-priced compilers. The TDI Modula-2/Amiga compiler retails for about half the price of comparable Aztec C compilers, at approximately $600 for the Commercial version and $270 for the Regular one. The most recent version is 3.00A, and fully supports the new 1.2 Enhanced Operating System. Popularity also relies on the need for more structured approaches to deal with the increasingly complex tasks confronting the microcomputer programmer. Modula-2 includes constructs for programming with machine-level bits and addresses, and for creating processes and switching between them. Also, you can break programs into modules for separate compilation, testing and debugging, thus making it easier to manage large projects and dividing them amongst a team of programmers. This increases the likelihood that any low-level, machine dependent components can be isolated, and easily changed, if portability is required. These features are defined in Modula-2 itself, rather than in extensions, making program portability a realistic goal. We will be glad to help you out with more information on Modula-2, if there is sufficient interest. In the meantime you might find the following books of use, if you can find them: Modula-2: A Seafarer's Guide and Shipyard Manual, by Edward J. Joyce, Addison-Welsey Publishing - this is THE BEST book on the Modula-2 language in general; it covers everything in an easy to read format and is injected with lots of humor. This book doesn't cover the Amiga specifics; you'll need the Amiga Tech. Ref. manuals and the TDI Modula-2 ref. manual to do any real Amiga programming; this contains a good history chapter and a conversion reference/discussion for Pascal programmers. Modula-2: Discipline and Design, by Arthur Sale from the University of Tasmania, Addison-Welsey Publishing - this book provides a first course in programming with Modula-2, and is suitable for self instruction. There are many programming examples and projects, illustrations and exercises. The appendixes and footnotes provide valuable reference material. It is also of interest to practising programmers wanting to learn about Modula-2 and how to exploit its features in large software engineering projects. Highly recommended. Modula-2 Programming, by Ogilvie, McGraw-Hill Publishing - this is a very complete hardback book; it is a little disorganized and it doesn't seem to have the humor that Seafarer's does. Modula-2 for Pascal Programmers, by R. Gleaves, Springer- Verlag - this is a good reference work for those familiar with Pascal, who want to switch over to Pascal. Modula-2: An Introduction, by Thalmann, Springer-Verlag. Modula-2 Programming, by Knepley and Platt, Prentice-Hall. All the Modula programs in this drawer, except for Compare, can be run from the icons. Lines, RectAngles and Colours run for a certain time then end and return to the workbench environment. Sparks and Trails can be controlled by menus or gadgets. We have had several requests to provide source code for all the utilities we use, but space make this prohibitive. However, if you ever find anything on MEGADISC for which you would like the source code, just write to us and we'll supply it - provided the author has no objections (for example, Greg Epley has provided me with the source code to all his programs, because I'm studying Modula-2, but he doesn't want it spread). We are most fortunate to have a couple of very useful utilities ,ie. Era and Compare, provided by Greg Epley, who wrote the well written "Sizzlers" graphic programs which you can find amongst the Fish Disks. We were so impressed with the way he presented "Sizzlers" that we wrote to him, and we've included an abridged copy of his reply below:-  From: Greg Epley, President/Certified Developer To: Ian Vanderfield Subject: MEGADISC response Surprised doesn't begin to express the receipt of your donation and the bonus issue of MEGADISC. I have had NO response from anyone here in the U.S. regarding my "Sizzlers" program (version 1.0 on Fish Disk #50). I am happy to help you out by sending software and other goodies from time to time. I have discovered that the new "Sizzlers" (Version 1.7 on Fish Disk #80) doesn't like V1.1 of the system software, but everybody in the U.S. is using 1.2 now, and I have to remain compatible. I suggest that you try to get your hands on 1.2 before you run any of the enclosed software. It is well worth the cost. I still find an occasional Guru that I have to re-boot on, but you can recover from some of them without a re-boot now. Memory is managed much better now too. As far as copyrights go, the main reason I'm applying them to everything is to legally prevent anyone from changing my software or any other part of the package (graphic designs, code fragments, documentation, etc.). I do not plan to copy-protect any of our software, even if it means losing some money. In my opinion, copy-protection is a waste of time, and in the long run, a waste of money having to invent new protection schemes which are broken shortly thereafter. All I ask is that you include the license.readme file, which pretty much covers everything, with anything you use. If you have further questions, please feel free to contact me about them. If you feel the need to make a donation from time to time it will be much appreciated, but the exposure received from your MEGADISC will help a lot. By the way, your MEGADISC looks EXCELLENT. I haven't seen any of the disk magazines from the U.S., but I have seen several PD disks, and most have half-completed or poorly written software on them. Your donation and kind comments have spurred me on, so I'll continue to do my best. Best of luck to you in your endeavors. -----------------------------------------------------------------  * Insight Software Development is a trademark of Insight Software Development, Lexington, North Carolina. ----------------------------------------------------------------- So it only remains to say cheerio for this issue, and we hope you find the programs both entertaining and useful. For our next issue we shall probably be bringing you C programs as several readers have requested (see letters in the I&O drawer). So if any of you have something written in C that you would like published, now is the time to send it in (we can't have the yanks being the only contributors to this All-Australian magazine!). ===========================END of the INTRO=============================