Unix wars

The Unix wars were the struggles between vendors of the Unix computer operating system in the late 1980s and early 1990s to set the standard for Unix thenceforth.

Although AT&T Corporation created Unix, by the 1980s, the University of California, Berkeley Computer Systems Research Group was the leading noncommercial Unix developer. In the mid-1980s, the three common versions of Unix were AT&T's System III, the basis of Microsoft's Xenix and the IBM-endorsed PC/IX, among others; AT&T's System V, which it sought to establish as the new Unix standard; and the Berkeley Software Distribution (BSD). All were derived from AT&T's Research Unix, but had diverged considerably. Further, each vendor's version of Unix was different to some degree.

For example, at a mid-1980s Usenix conference, many AT&T staff had buttons which read "System V: Consider it Standard" and a number of major vendors were promoting products based on System V. On the other hand, System V did not yet have TCP/IP networking built in and BSD 4.2 did; vendors of engineering workstations were nearly all using BSD and posters that said "4.2 > V" were available.

A group of vendors formed the X/Open standards group in 1984, with the aim of forming compatible open systems. They chose to base their system on Unix.

X/Open caught AT&T's attention. To increase the uniformity of Unix, AT&T and leading BSD Unix vendor Sun Microsystems started work in 1987 on a unified system. (The feasibility of this had been demonstrated a few years earlier by the US Army Ballistic Research Laboratory's System V environment for BSD Unix.) This was eventually released as System V Release 4 (SVR4).

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