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Developer(s)Ullrich von Bassewitz
Initial releaseNovember 15, 1998; 22 years ago (1998-11-15)[1]
Stable release
2.19 / November 20, 2020; 10 months ago (2020-11-20)
Written inANSI C
Operating systemMultiplatform
TypeCross compiler
Licensezlib license

cc65 is a cross development package for 6502 and 65C02 targets, including a macro assembler, a C cross compiler, linker, librarian and several other tools.


cc65 is based on a native C compiler that was originally adapted for the Atari 8-bit computers by John R. Dunning in 1989, which originated as a Small C descendant. It has several extensions, and some of the limits of the original Small C compiler are gone.

The toolkit has largely been expanded by Ullrich von Bassewitz and other contributors. The actual cc65 compiler, a complete set of binary tools (assembler, linker, etc.) and runtime library are under a license identical to zlib's.[2] The ca65 cross-assembler is one of the most powerful 6502 cross-assemblers available under an open-source license.[citation needed]

The compiler itself comes close to ANSI C compatibility, while C library features depend on the target platform's hardware. stdio is supported on many platforms, as is Borland-style conio.h screen handling. GEOS is also supported on the Commodore 64 and even the Apple II. The library supports many of the Commodore platforms (C64, C128, C16/116/Plus/4, P500 and 600/700 family), Apple II family, Atari 8-bit family, Oric Atmos, Nintendo Entertainment System, Watara Supervision game console and Ohio Scientific Challenger 1P.[3]

Officially supported host systems include Linux, Microsoft Windows, MS-DOS and OS/2, but the source code itself has been reported[by whom?] to work almost unmodified on many platforms beside these.

The ca65 macro assembler supports 6502, 65C02, and 65C816 processors, and can be used standalone without the C compiler.[4]

Supported API[edit]


  • conio (text-based console I/O non-scrolling)
  • dio (block-oriented disk I/O bypassing the file system)


  • em (expanded memory, used for all kinds of memory beyond the 6502's 64K barrier, similar EMS)
  • joystick (relative input devices)
  • mouse (absolute input devices)
  • serial (communication)
  • tgi (2D graphics primitives inspired by BGI)
conio dio emd joy mou ser tgi
apple2 Yes Yes 1 1 1 1 2
apple2enh Yes Yes 1 1 1 1 2
atari Yes Yes 2 15[5]
atmos Yes 1
c16 Yes 1 1
c64 Yes 6 4 3 1 1
c128 Yes 5 2 3 1 2
cbm510 Yes 1 1 1
cbm610 Yes 1 1
geos Yes Yes 1 1 1
lynx 1 1 1
nes Yes 1 1
osi Yes
pet Yes 1
plus4 Yes 1 1
vic20 Yes 2

Note: For static libraries, "Yes" means the feature is available. For dynamic libraries, the columns list the number of available drivers.


External links[edit]