Editing Dartmouth BASIC (section)

===Sixth Edition===
Work on the Sixth Edition began in the fall of 1969 before the Fifth Edition was finalized. A complete specification was written beforehand for the new version. This contrasts with previous versions where the specification documents were based on the changes in the compiler. This version was worked on by Kemeny and Kurtz as well as several former students who returned as faculty: Stephen Garland, John McGeachie, and Robert Hargraves. It was given considerable time to mature, with a beta version running for three months during the summer of 1971, before it was finally released on 21 September 1971. As a result of this maturity, Kurtz described it as "probably the best-designed and most stable software system Dartmouth has ever written."{{sfn|Kurtz|1981|p=531}}

One of the biggest changes was the replacement of the earlier <code>CHAIN</code> concept with the much better-defined <code>CALL</code> which operated in a fashion similar to <code>GOSUB</code>, but it referred to a function name rather than a line number. The functions were defined using <code>SUB...SUBEND</code>, and took arbitrary [[Parameter (computer programming)|parameters]] in the call rather than using [[global variable]]s via <code>COMMON</code> declarations. Another major change was to use file handles (numbers) created with the <code>FILE</code> command which is similar to <code>OPEN</code> which is found in most modern BASICs.<code>PRINT USING</code> provided formatted output in a fashion somewhat similar to FORTRAN,{{sfn|Elliott|1988|p=134}} while {{code|LINPUT}} accepted input with no interpretation, allowing commas, semicolons, and even BASIC code to be typed in.{{sfn|Kemeny|Kurtz|1985|p=26}}

The Sixth Edition was essentially the last version of the original BASIC concept. It remained unchanged for many years. Later versions were significantly different languages.{{sfn|Kurtz|1981|p=531}}