Turbo-BASIC XL is an enhanced version of the BASIC programming language for Atari 8-bit computers. It is a compatible superset of the Atari BASIC that shipped with the computers. Turbo-Basic XL was developed by Frank Ostrowski which shipped with all Atari 8-bit models, led to a market for 3rd party BASIC interpreters and compilers with better performance or more commands. Among them was an official port of Microsoft BASIC sold by Atari, Inc. and several improved versions released by Optimized Systems Software, who had written the original Atari BASIC under contract. There were also Atari BASIC compilers from several companies.
Turbo-Basic XL was a late entry to this list, first published in December 1985 as type-in program in Happy Computer magazine. It came in both interpreter and compiler versions. Turbo-Basic XL takes advantage of the extra memory of the XL (and later XE) series machines, preventing it from running on the original 400 and 800. A version supporting those systems was later released as Frost BASIC (short for "Frank Ostrowski").
The internal disk-related commands are tied to particular versions of DOS. A number of ports to different versions of DOS became available.
Performance
The most notable feature of Turbo-Basic was its dramatically improved speed; an unmodified Atari BASIC program loaded into Turbo-Basic would normally run three to five times faster,