| Research Unix | |
|---|---|
| V6 | (1975) |
| V7 | (1979) |
| V8 | (1985) |
| V9 | (1986) |
| V10 | (1989) |
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| CB UNIX | (c. 1975) |
| PWB/UNIX | (1977) |
| System III | (1982) |
| IX | (1988) |
Sixth Edition Unix, also called Version 6 Unix or just V6, was the first version of the Unix operating system to see wide release outside Bell Labs. It was released in May 1975 and, like its direct predecessor, targeted the DEC PDP-11 family of minicomputers. It was superseded by Version 7 Unix in 1978/1979.
Bell Labs developed several variants of V6, including the stripped-down MINI-UNIX for low-end PDP-11 models, LSI-UNIX or LSX for the LSI-11, and the real-time operating system UNIX/RT, which merged V6 Unix and the earlier MERT hypervisor.[1]
An enhanced V6 was the basis of the first ever commercially sold Unix version, INTERACTIVE's IS/1. Bell's own PWB/UNIX 1.0 was also based on V6, where earlier (unreleased) versions were based on V4 and V5. Whitesmiths produced and marketed a (binary-compatible) V6 clone under the name Idris.
Since source code was available and the license was not explicit enough to forbid it, V6 was taken up as a teaching tool, notably by the University of California, Berkeley and the University of New South Wales (UNSW). Berkeley distributed a set of add-on program called the First Berkeley Software Distribution or 1BSD, which later became a full-fledged operating system. UNSW professor John Lions' famous Commentary on UNIX 6th Edition was an edited selection of the main parts of the kernel as implemented for a Digital PDP-11/40, and was the main source of kernel documentation for many early Unix developers. Due to license restrictions on later Unix versions, the book was mainly distributed by samizdat photo-copying. Also in New South Wales, a group at Wollongong University completed a port to the Interdata 7/32 in 1977 called Wollongong Interdata UNIX, Level 6, thus proving the portability of Unix and its new systems programming language C. A Bell Labs port to the Interdata 8/32 was not released. The University of Sydney released the Australian Unix Share Accounting Method (AUSAM) in November 1979, a V6 variant with improved security and process accounting.
In the Eastern Bloc, clones of V6 Unix appeared for local-built PDP-11 clones (MNOS, later augmented for partial compatibility with BSD Unix) and for the Elektronika BK personal computer (BKUNIX, based on LSX).
The code for the original V6 Unix has been made available under a BSD License under agreement from the SCO Group; see Ancient UNIX Systems.
After AT&T decided the distribution by Bell Labs of a number of pre-V7 bug fixes would constitute support (disallowed by an antitrust settlement) a tape with the patchset was slipped to Lou Katz of USENIX, which distributed them.[2]
V6 was used for teaching at MIT in 2002 through 2006, and subsequently replaced by an x86 clone called xv6.
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