BASIC A+

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| developer = Optimized Systems Software

| released = {{Start date and age|1983}}

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| operating system = Atari 8-bit

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| genre = BASIC

| license = Copyright © 1983 Optimized Systems Software Proprietary

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BASIC A+ is an implementation of the BASIC programming language for Atari 8-bit computers introduced by Optimized Systems Software in 1981. It was developed by the team that created Atari BASIC, which shipped with each computer, and is compatible. BASIC A+.{{cite magazine |last=DeVore |first=Richard |title=Product Reviews, BASIC A+ |journal=Antic |date=May 1983 |volume=2 |issue=2 |url= http://www.atarimagazines.com/v2n2/productreviews.html}} BASIC A+ adds new features to the language, such as IF..ELSE..ENDIF statements, support for hardware features like player/missile graphics, and commands for debugging. While Atari BASIC is an 8 KB ROM cartridge, BASIC A+ is floppy disk based and uses 15 KB of the computer's RAM, leaving 23 KB available for user programs in a 48 KB Atari 800. BASIC A+ shipped with a supplement to the Atari BASIC reference manual as its documentation.

Optimized Systems Software followed BASIC A+ with the cartridge-based BASIC XL, then BASIC XE.