ARCHIVED: In Unix, what are Version 6 and Version 7?

Versions 6 and 7 (aka V6 and V7) represent the foundations upon which both major Unix flavors (BSD and System V) and all modern implementations are based. Their names refer to editions of internal documentation at Bell Laboratories, and the two releases are sometimes referred to as the Sixth and Seventh Editions. Neither V6 nor V7 were commercial products, nor were they officially supported by Bell Laboratories. Version 6 (1975) was the first Unix distribution widely available outside of AT&T; academic and research institutions could obtain the C source free of charge. In particular, the University of California at Berkeley made extensive modifications and improvements to the code, which became the Berkeley Software Distribution (BSD). In 1979, Bell released Version 7, which incorporated some of Berkeley's improvements and was the first Unix to really emphasize portability. Version 7 also formed the new basis for future BSD releases and was more or less the direct ancestor of System V.

In the middle 1980s, AT&T finally offered its first officially supported Unix. Its commercial Unix releases (notably System III and System V) were based on Versions 6 and 7, but represented a separate line of development. Internal research continued beyond the Seventh Edition, extending to Version 10, but this "V Series" had little influence outside the company.