cc65 is a complete cross development package for 65(C)02 systems, including a powerful macro assembler, a C compiler, linker, librarian and several other tools.
cc65 has C and runtime library support for many of the old 6502 machines, including
- the following Commodore machines:
- VIC20
- C16/C116 and Plus/4
- C64
- C128
- CBM 510 (aka P500)
- the 600/700 family
- newer PET machines (not 2001).
- the Apple ][+ and successors.
- the Atari 8 bit machines.
- GEOS for the C64 and C128.
- the Nintendo Entertainment System (NES).
- the Supervision console.
- the Oric Atmos.
- the Lynx console.
The libraries are fairly portable, so creating a version for other 6502s shouldn't be too much work.