DOWNLOADING and CHOPPING TIPS

By Mike Lawrence

     There are some tricks to successfully downloading Amiga 
programs. Most Amiga users who do downloading are probably using 
Xmodem protocol. The problem with standard Xmodem protocol is that 
it does not provide for removal of any extra characters on the end 
of the file. (Xmodem transfers data in 128-character blocks, so 
unless the original file that was uploaded was an exact multiple 
of 128 characters long, there will be some extra characters on the 
end of the file.) The Amiga gets upset when you tell it to run a 
file with extra characters on the end and gives you a "Unable to 
load <filename>: file is not an object module" error message. 
(Note that at least one terminal program (Maxicomm) has a special 
non-standard Xmodem protocol that properly handles making sure the 
file you download is the same length as the file that was uploaded, 
but unless you AND the person who did the uploading use Maxicomm, 
this just creates additional problems for you.)
     There are several ways to solve this problem. We have several 
programs in the club library for chopping the file back down to 
length. One is called fixobj, and is suppossed to automatically 
chop the file to the correct length. Sometimes it works; sometimes 
it makes an output file that is empty. Another program we have is 
called trunc, and it always works, PROVIDED you know what the 
correct length for the file is. Most of the time on CompuServe, 
the person who uploads the file leaves a note in the description 
of the program that tells what the proper file length is. If you 
know the length, then just run trunc and you'll have a program 
that should run. But what if you don't know the correct length? 
What follows is a description of a chopping method that has so far 
always worked for me, but beware that, with some combinations of 
terminal programs and BBS's, this technique might not work (I use 
aterm5 from the club library, and do most of my downloading from 
CompuServe.) However, if you have a file you just spent an hour 
downloading and can't do a thing with, you don't have anything to 
lose by giving this technique a try.
     1. Suppose you have downloaded a file named term2 and get the 
"file is not an object module" message when you try to run it.
     2. Get into CLI, and open up the CLI window nice and big, and 
then type: type term2 opt h, and just wait until the screen stops 
scrolling.
     3. On the left side of the screen is the hex representation 
of the file. On the end of the file, there should be a bunch of 
1A characters. (This is the Amiga "end of file" character, decimal 
value 26.)
     4. Start at the end of the file and count the number of 1A 
characters, until you get to something besides 1A. Write this 
number down.
     5. Type:list p=term2 to see the length of the unchopped file 
(it's the first number to the right of the filename).
     6. Subtract the number of 1A characters you counted earlier 
from the length of the unchopped file, and use this as the length 
with the trunc program to chop the file.type: trunc term2 
term2.exe length
     7. You should now be able to type term2.exe, and run the 
program.
     8. Once you verify that the term2.exe file works, you can 
delete the term2 file.
       Happy downloading!