Richard Stallman announces plans for the GNU (GNU's not Unix) operating system, a Unix look-alike composed of free software.

1984

At the Winter USENIX/UniForum meeting, AT&T describes its support policy for Unix: "No advertising, no support, no bug fixes, payment in advance."

X/Open Co., a European consortium of computer makers, is formed to standardize Unix in the X/Open Portability Guide.

1985

AT&T publishes the System V Interface Definition (SVID), an attempt to set a standard for how Unix works.

1986

Rick Rashid and colleagues at Carnegie Mellon University create the first version of Mach, a replacement kernel for BSD Unix intended to create an operating system with good portability, strong security and use in multiprocessor applications.

1987

AT&T Bell Labs and Sun Microsystems announce plans to co-develop a system that would unify the two major Unix branches.

Andrew Tanenbaum writes Minix, an open-source Unix clone for use in computer science classrooms.

1988

The "Unix Wars" are underway. In response to the AT&T/Sun partnership, rival Unix vendors including DEC, HP and IBM form the Open Software Foundation (OSF) to develop open Unix standards. AT&T and its partners then form their own standards group, Unix International.

The IEEE publishes Posix (Portable Operating System Interface for Unix), a set of standards for Unix interfaces.

1989

Unix System Labs, an AT&T Bell Labs subsidiary, releases System V Release 4 (SVR4), its collaboration with Sun that unifies System V, BSD, SunOS and Xenix.

1990

The OSF releases its SVR4 competitor, OSF/1, which is based on Mach and BSD.

1991

Sun Microsystems announces Solaris, an operating system based on SVR4.

Linux Torvalds writes Linux, an open-source OS kernel inspired by Minix.

1992

The Linux kernel is combined with GNU to create the free GNU/Linux operating system, which many refer to as simply "Linux."

1993

AT&T sells its subsidiary Unix System Laboratories and all Unix rights to Novell. Later that year Novell transfers the Unix trademark to the X/Open group.

Microsoft introduces Windows NT, a powerful 32-bit multiprocessor operating system. Fear of NT will spur true Unix standardization efforts.

1994

NASA invents Beowulf computing based on inexpensive clusters of commodity PCs running Unix or Linux on a TCP/IP LAN.

1996

X/Open merges with Open Software Foundation to form The Open Group.

1999

U.S. President Clinton presents the National Medal of Technology to Ken Thompson and Dennis Ritchie for their work at Bell Labs.

2002

The Open Group announces Version 3 of the Single UNIX Specification (formerly Spec 1170).

Sources: Peter H. Salus, A Quarter Century of Unix ; Microsoft; AT&T; The Open Group, Wikipedia and other sources.

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