Unix wars

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Unix genealogy tree

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. These battles are commonly said to have harmed the market acceptance of Unix and created a market gap that allowed the rise of Windows NT.

In the mid-1980s, the two common versions of Unix were BSD, from the University of California, Berkeley, and System V, from AT&T. Both were derived from the earlier Version 7 Unix, but had diverged considerably (this conflict was also known as the "UNIX wars" to some degree). Further, each vendor's version of Unix was different to a greater or lesser degree.

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 U.S. Army Ballistic Research Laboratory's System V environment for BSD Unix.) This was eventually released as System V Release 4 (SVR4).

While this decision was applauded by customers and the trade press, other Unix licensees feared Sun would be unduly advantaged. They formed the Open Software Foundation (OSF), which released OSF/1, more closely based on BSD. AT&T and another group of licensees then formed UNIX International.

Technical issues soon took a back seat to vicious and public commercial competition between the two competing "open" versions of Unix, with X/Open holding the middle ground.

In March 1993 the major participants in UI and OSF formed the Common Open Software Environment (COSE) alliance, effectively marking the end of the most significant era of the Unix wars. This was followed shortly thereafter by the completion of the sale of AT&T's UNIX assets to Novell in June, and Novell's transfer of the Unix brand to X/Open in October. The following year, UI and OSF merged, with the combined entity retaining the OSF name.

In 1996, X/Open and the new OSF merged to form the Open Group. COSE work such as the Single UNIX Specification, the current standard for branded Unix, is now the responsibility of the Open Group. However, the damage to Unix's market reputation had been done.

Since then, occasional bursts of Unix factionalism have broken out, such as the 1996 HP/SCO "3DA" alliance, and Project Monterey in 1998, a teaming of IBM, SCO, Sequent and Intel which was in turn followed by litigation (SCO v. IBM) between IBM and the new SCO, formerly Caldera.