The GEOS operating system managed to clone the Macintosh GUI on the Commodore 64, a computer with an 8 bit CPU and 64 KB of RAM. Based on Maciej Witkowiak's work, I created a reverse-engineered source version of the C64 GEOS 2.0 KERNAL for the cc65 compiler suite:
- The source compiles into the exact same binary as shipped with GEOS 2.0.
- The source is well-structured and split up into 31 source files.
- Machine-specific code is marked up.
- Copy protection/trap mechanisms can be disabled.
- The build system makes sure binary layout requirements are met.
This makes the source a great starting point for
- adding (optional) optimized code paths or features
- integrating existing patches from various sources
- integrating versions for other computers
- porting it to different 6502-based computers
Just fork the project and send pull requests!