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.

Direct library support (that is, startup/initialization code) and
support libraries for other features are available for...

 - the Commodore C64
 - the GEOS operating system for the Commodore C64
 - the Commodore C128
 - the Commodore C16, C116 and Plus/4
 - the Commodore P500
 - the Commodore 600/700 family of computers
 - the Apple ][
 - the Atari 8bit machines
 - the Oric Atmos
 - the Nintendo Entertainment System (NES)
 - the Supervision Game Console
 - the Atari Lynx Console