Workshop:Amiga, Pascal, graphics.library and timer.device

Respect the copyright

This workshop is based on the workshop titled "Retrocoding: Amiga, C, graphics.library und timer.device" which is written and copyrighted by Kai Scherrer.

The workshop you read here is a translation into English from the work done by Kai. The original workshop was aimed at the c-programmer and also this part has been rewritten here to address the Pascal programmer instead.

That means that the workshop here contains some changes in comparison to the original work done by Kai. The translation and changes respects and upholds original authors copyright.

Let's start with clarifying something first: Everything read in this lead section is written by me (the translator). That also means that text listed in and after the table of contents is based on the work written by original author.

This should hopefully clear things up with regards of the use of the words "I", "we" and "me".

This document is a translation (from German to English, changed programming language from c to Pascal) of a programming workshop for the Amiga, originally written by Kai Scherrer.

The original author wrote this tutorial for the c programming language as well as introduced the reader to different c-compilers for the Amiga as well as discussed their advantages/disadvantages and/or usage.

Because this document is targeting users that (want to) program using the Pascal language, there are many difference in comparison to the original documentation. As you perhaps might have noticed, these differences begin right from the start including this foreword.

notes with regards to Free Pascal

This documentation is aimed at those using the Free Pascal compiler. This compiler is able to run on a variety of operating systems including Amiga, AmigaOS, AROS and MorphOS (so you can use the compiler natively), but can also be used to cross-compile f.e. from Windows, Mac and/or Linux to target the aforementioned platforms.

Another wicked alternative for compiling single-file projects is using the online compiler. There is even a special version of the online compiler for old browsers that don't quite handle javascript

Note that the original author used vbcc for his workshop and that Free Pascal is able to use the same back-end (vasm/vlink) that is used by vbcc to create executables. In fact this is default when compiling natively on Amiga for example.

Free Pascal uses some defaults that might not always be obvious for most. For example, current API units automatically opens and closes libraries for you when you include such a unit in your project. The auto-opening and closing is something that usually isn't done for most programming languages targeting the Amiga platform.

Another note worth mentioning is the fact that Pascal does not has a dedicated program entry point by the name of main. As such, there is also no main header declaration. But, if you have your roots in c-programming and can't live without main() then this can easily be accommodated, for example:

// c main like entry-point.
function main(argc: Integer; argv: PPChar): integer;
begin
  if EverthingElseWentOk() 
    then result := RETURN_OK 
      else result := RETURN_FAIL;
end;

// This is the Pascal equivalent of main program entry point
begin
  ExitCode := main(ArgC, ArgV);
end.

Note that Pascal uses the identifier ExitCode to return a value to the shell but also realize that ArgC and ArgV can't be used to distinguish between program-startup from shell or WB (red: is that true ?)