an 8 KB ROM cartridge for use with the 1979 Atari 400 and 800 computers. Starting with the 600XL and 800XL in 1983, BASIC is built into the system. There are three versions of the software: the original cartridge-based "A", the built-in "B" for the 600XL/800XL, and the final "C" version in late-model XLs and the XE series. They only differ in terms of stability, with revision "C" fixing the bugs of the previous two.

Despite the Atari 8-bit computers running