• Hello, Guest! Welcome back, and be sure to check out this post for more info about the recent service interruption and migration.

Writing programs for GS/OS?


Well-known member
Is there a good book or resource plus toolchain on writing Apple IIgs GS/OS programs in C somewhere? and being able to utilize external hardware/cards as well? 

Just wondering. Thanks. 

Last edited by a moderator:


Well-known member
Most low level stuff is going to be 65816 ASM. Roger Wagner's "Beginner's Guide To Apple IIgs Machine Language Programming" is a good start (uses Merlin 16 syntax).


Toolbox programming in both ASM and C.


More here: https://apple2.gs/library.php

Note that many of these books predate GS/OS, but focus on the end user Toolbox functions which are mostly unchanged. Low level stuff is going to be dated 1990 or newer to be relevant with GS/OS System 6.0.x. Don't bother with ProDOS 16, aside from a few references in newer docs, its been completely superseeded by GS/OS. The Apple Tech Notes relating to the IIgs and GS/OS are very important as they amend the official reference docs.

As for dev tools, they are still available from The Byte Works to purchase (ORCA/C) or you can use MPW/APW. https://juiced.gs/store/category/software/

For ASM, Merlin 16+ is the way to go on the machine itself or Merlin 32 if you want to cross assemble: https://brutaldeluxe.fr/products/crossdevtools/merlin/



Well-known member
Also of interest is GNO/ME, the "unix like" environment that runs on top of GS/OS: http://www.gno.org/gno/

If you plan on playing with it for porting *nix stuff, just be aware that there are issues with some of the header files included with GNO/ME 2.0.6, I'd stick with 2.0.4.