OSF/1

OSF/1 is a variant of the Unix operating system that was largely a product of the so-called "Unix wars" of the mid- and late 1980s. OSF/1's roots lie in being one of the first operating systems to use the Mach kernel developed at Carnegie Mellon University.

In 1988, IBM, DEC, HP, and others formed the Open Software Foundation to develop a version of Unix to compete with AT&T and Sun Microsystems. This Unix version, OSF/1 (named after the Open Software Foundation), was soon refined and became known as Digital Unix. OSF/1 is probably best known as the root of the third major branch of the Unix family tree, after System V and BSD.

In 1994, the Open Software Foundation ceased funding of research and development of what had become Digital Unix. The descendant of OSF/1, Tru64, now belongs to Hewlett-Packard's collection of intellectual property and isn't used much anymore.