Atari shipped a final Rev C basic both in the ROMs for the XE computers and on cartridges for people that requested it. There were several derivations. The or

Atari shipped a final Rev C basic both in the ROMs for the XE computers and on cartridges for people that requested it. There were several derivations. The original authors of Atari Basic produced BASIC XL and BASIC XE on cartridge, each with additional language features. There's also the really cool Altirra BASIC (see https://virtualdub.org/downloads/Altirra%20BASIC%20Reference%20Manual.pdf https://virtualdub.org/downloads/Altirra%20BASIC%20Reference...) which ships with the Altirra emulator as a tokenized-code compatible, but faster and more featureful, implementation. A version of that was included in the ROM for the new 576NUC+ all-in-one Atari-compatible.