Forty years after its birth, Unix still stands as one of the defining creations in computing. Its history is not a straight line but a long sequence of technical breakthroughs, forks, standards battles, commercial turns, and lasting ideas. What follows is a year-by-year record of the milestones that shaped Unix and the systems that grew out of it.
1956
A U.S. Justice Department consent decree restricted AT&T from entering businesses beyond its role as a public carrier providing communications services. That limitation would later affect how Unix was distributed and commercialized.
1969
March — Bell Labs, part of AT&T, withdrew from the Multics project (Multiplexed Information and Computing Service), an ambitious but highly complex time-sharing operating system. Several important ideas from Multics would later reappear in Unix.
August — Ken Thompson at Bell Labs wrote the first version of a new operating system, still unnamed at the time, in assembly language for the DEC PDP-7 minicomputer.
1970
Thompson's operating system was given the name Unics, short for Uniplexed Information and Computing Service—essentially a cut-down, miniature counterpart to Multics. At some point, the name evolved into Unix.
1971
February — Unix was ported to the DEC PDP-11.
November — Ken Thompson and Dennis Ritchie completed and published the first edition of the Unix Programmer's Manual.
1972
Dennis Ritchie developed the C programming language, which would soon become inseparable from Unix itself.
1973
Unix reached a more mature stage. This was the year of pipes, the mechanism that lets programs pass data directly from one to another—an idea that influenced operating systems for decades.
Unix was also rewritten in C, a decisive step that greatly improved its portability and long-term impact.
1974
January — The University of California, Berkeley received a copy of the Unix source code.
July — Dennis Ritchie and Ken Thompson published "The UNIX Time-Sharing System" in the journal of the Association for Computing Machinery. They described Unix as a "general-purpose, multi-user, interactive operating system." That paper sparked broad interest and demand for Unix.
1976
Bell Labs programmer Mike Lesk created UUCP (Unix-to-Unix Copy Program), a tool for file transfer over networks that also became important for email and the global news system later known as Usenet.
1977
Unix was ported beyond DEC hardware to Interdata 8/32 and IBM 360 systems, proving that it could live outside the platform where it was born.
1978
Bill Joy, a Berkeley graduate student, released 1BSD, the first Berkeley Software Distribution. In essence, it was Bell Labs Unix Version 6 with additional software.
BSD quickly became a serious Unix branch in its own right, emerging as a counterpart to AT&T's Unix. Its descendants would later include FreeBSD, NetBSD, OpenBSD, DEC Ultrix, SunOS, NeXTSTEP/OpenStep, and eventually Mac OS X.
1980
Funded by DARPA, 4BSD became the first Unix system in the world to support TCP/IP.
1982
Bill Joy co-founded Sun Microsystems, which went on to build Unix-based Sun workstations.
1983
AT&T released the first version of Unix System V, one of the most influential Unix lines. It later gave rise to systems such as IBM AIX and HP-UX.
The same year, Ken Thompson and Dennis Ritchie received the ACM Turing Award for their work on operating systems theory and specifically for implementing Unix.
Richard Stallman also announced plans for GNU—"GNU's Not Unix"—a free software operating system designed to resemble Unix.
1984
In winter, at the USENIX/UniForum conference, AT&T outlined its Unix policy in blunt terms: no advertising, no support, and no patches without payment first.
Meanwhile, X/Open, a consortium of European computer manufacturers, introduced the X/Open Portability Guide, an attempt to define Unix-related standards and improve application portability where existing standards were incomplete.
1985
AT&T published the System V Interface Definition (SVID), an effort to standardize how a Unix system should behave.
1986
At Carnegie Mellon University, Rick Rashid and colleagues created the first version of Mach, an operating system intended to replace the BSD Unix kernel with something more portable, more secure, and better suited to multiprocessing.
1987
AT&T Bell Labs and Sun Microsystems announced plans to work together on an operating system that could unify the two major Unix branches.
At about the same time, Andrew Tanenbaum wrote Minix, an open Unix-like system created for computer science teaching.
1988
The Unix wars began. In response to the AT&T/Sun alliance, other Unix vendors—including DEC, HP, and IBM—formed the Open Software Foundation (OSF) to pursue an open Unix standard. AT&T and its allies answered with their own organization, Unix International.
That same year, the IEEE published POSIX (Portable Operating System Interface for Unix), a family of standards defining Unix interfaces.
1989
Unix System Laboratories, then part of AT&T Bell Labs, released System V Release 4 (SVR4). Developed in cooperation with Sun, it combined elements of System V, BSD, SunOS, and Xenix.
1990
The Open Software Foundation responded to SVR4 with OSF/1, a system built on Mach and BSD foundations.
1991
Sun Microsystems announced Solaris, an operating system based on SVR4.
That same year, Linus Torvalds wrote Linux, an open-source operating system kernel inspired by Minix.
1992
The Linux kernel was combined with GNU, giving rise to the free GNU/Linux operating system, commonly referred to simply as Linux.
1993
AT&T sold Unix System Laboratories and its Unix rights to Novell. Novell later transferred the Unix trademark to the X/Open Group.
In the same year, Microsoft developed Windows NT, a powerful 32-bit multiprocessing operating system. The pressure created by Windows NT helped push Unix vendors toward stronger standardization.
1994
NASA developed Beowulf computing, a low-cost clustering approach built from inexpensive PCs using Unix or Linux as the operating system and TCP/IP for networking.
1996
X/Open and the Open Software Foundation merged to form The Open Group.
1999
U.S. President Bill Clinton awarded Ken Thompson and Dennis Ritchie the National Medal of Technology in recognition of their work at Bell Labs.
2001
Apple released Mac OS X, a desktop operating system built on the Mach kernel and BSD foundations.
2002
The Open Group announced the third version of the Single UNIX Specification, previously known as Spec 1170.
From an unnamed operating system on a PDP-7 to a family tree that includes BSD, System V, Solaris, Linux, and Mac OS X, Unix left its mark not just through products, but through ideas: portability, composability, multiuser design, networking, and standards. Forty years on, its influence was everywhere.