Editing Atari BASIC (section)

===Releases===
The version Shepardson gave to Atari for the CES demo was not intended to be final, and Shepardson continued to fix bugs.{{sfn|Wilkinson|1982|p=x}} Unknown to Shepardson, Atari had already sent the CES version to manufacturing.{{sfn|Wilkinson|1982|p=vi}}

This version was later known as '''Revision A'''. It contains a major bug in a routine that copies memory: deleting lines of code that are exactly 256 bytes long causes a lockup after the next command is entered. The {{keypress|Reset}} key does not fix it.<ref name=twoline>{{cite magazine |url=http://www.atarimagazines.com/compute/issue74/readers_feedback_10.php |title=Atari BASIC Bugs |magazine=Compute! |date=July 1986 |page=10}}</ref>

'''Revision B''' attempted to fix the major bugs in Revision A and was released in 1983 as a built-in ROM in the 600XL and 800XL models. While fixing the memory copying bug, the programmer noticed the same pattern of code in the section for inserting lines, and applied the same fix. This instead introduced the original bug into this code. Inserting new lines is much more common than deleting old ones, so the change dramatically increased the number of crashes.<ref name=twoline/> Revision B also adds 16 bytes to a program every time it is <code>SAVE</code>d and <code>LOAD</code>ed, eventually causing the machine to run out of memory for even the smallest programs.<ref name="rad">{{Cite magazine |last=Radcliff |first=Matthew |date=September 1985 |title=Revision C Converter |url=https://www.atarimagazines.com/v4n5/revisioncconverter.html |magazine=Antic |access-date=2023-07-08}}</ref>{{sfn|Chadwick|1985|p=230}} ''[[Mapping the Atari]]'' described these as "awesome bugs" and advised Revision B owners "Don't fool around; get the new ROM, which is available on cartridge" from Atari.{{sfn|Chadwick|1985|p=230}} The book provides a [[type-in program]] to patch Revision B to Revision C for those without the cartridge.{{sfn|Chadwick|1985|pp=250-251}}

'''Revision C''' eliminates the memory leaks in Revision B.{{sfn|Chadwick|1985|p=230}} It is built-in on later versions of the 800XL<ref name=rad/> and all XE models including the XEGS. Revision C was also available as a cartridge.{{sfn|Chadwick|1985|p=230}}

The version can be determined by typing <code>PRINT PEEK(43234)</code> at the READY prompt. The result is <code>162</code> for Revision A, <code>96</code> for Revision B, and <code>234</code> for Revision C.<ref>{{cite magazine |first=Bob |last=Hardy |title= Keycode Getter |url=https://www.atarimagazines.com/atariclassics/v2n1/keycode.php |magazine=Atari Classics |date= February 1993 |page=18}}</ref>