UNIX Past

A look at the key moments and history behind the UNIX operating system.

...a punning colleague called UNICS... an 'emasculated Multics'.

Unix was born in 1969... this paper presents a technical and social history of the evolution of the system.

...the number of UNIX installations has grown to 10, with more expected...

Since escaping AT&T's Bell Laboratories in the early 1970s, the UNIX system's influence has been immense. Universities, research institutes, and companies used it to pioneer technologies that are now essential—from CAD and lab simulations to the very foundation of the Internet.


A Fragmented Landscape

By the late 1970s, graduates who had used UNIX systems in university labs entered the workforce and demanded it. In response, vendors marketed their own diverging, incompatible versions of the system. The UNIX® trademark was ubiquitous, but it was applied to a multitude of different products that couldn't work together.

The Rise of Open Systems

Concerned by market fragmentation, a group of vendors formed X/Open in 1984 to define a comprehensive "open systems" environment based on agreed-upon standards. They chose the UNIX system as the foundation, creating a clear industry need for a single, standard version. The question was: which one?

Open systems were those that would meet agreed specifications or standards. This resulted in the formation of X/Open Company Ltd whose remit was, and today in the guise of The Open Group remains, to define a comprehensive open systems environment.

The UNIX Wars

In 1987, AT&T and Sun Microsystems formed a pact to unify the market around their version. Fearing this alliance, the rest of the industry formed the competing Open Software Foundation (OSF). The resulting "UNIX Wars" divided the community between AT&T's UNIX System V and the OSF's OSF/1, while X/Open held the neutral center ground.

Towards a Unified Standard

In a pivotal move, Novell (which had acquired AT&T's UNIX System Laboratories) transferred the rights to the UNIX trademark to the vendor-neutral X/Open in 1993. This separated the brand from any single company's code. By 1995, X/Open introduced the UNIX 95 brand, guaranteeing that certified systems met the Single UNIX Specification—a mission The Open Group continues today.

Timeline of a Revolution

Key milestones in the history of the UNIX system.

1969The Beginning
UNIX history starts back in 1969, when Ken Thompson, Dennis Ritchie and others started working on the "little-used PDP-7 in a corner" at Bell Labs.
1971First Edition
It had an assembler for a PDP-11/20, file system, fork(), roff and ed. It was used for text processing of patent documents.
1973Fourth Edition
It was rewritten in C. This made it portable and changed the history of OS's.
1975Sixth Edition
Also known as Version 6, this is the first to be widely available out side of Bell Labs. The first BSD version (1.x) was derived from V6.
1979Seventh Edition
It was a "improvement over all preceding and following Unices" [Bourne]. It had C, UUCP and the Bourne shell. It was ported to the VAX.
1980Xenix
Microsoft introduces Xenix. 32V and 4BSD introduced.
1982System III
AT&T's UNIX System Group (USG) release System III, the first public release outside Bell Laboratories. SunOS 1.0 ships. HP-UX introduced.
1983System V
AT&T announces UNIX System V, the first supported release. Installed base 45,000.
19844.2BSD
University of California at Berkeley releases 4.2BSD, includes TCP/IP, new signals and much more. X/Open formed.
1984SVR2
System V Release 2 introduced. At this time there are 100,000 UNIX installations around the world.
19864.3BSD
4.3BSD released, including internet name server. SVID introduced. NFS shipped. AIX announced. Installed base 250,000.
1987SVR3
System V Release 3 including STREAMS, TLI, RFS. At this time there are 750,000 UNIX installations around the world.
1988POSIX.1
POSIX.1 published. Open Software Foundation (OSF) and UNIX International (UI) formed.
1989System V
AT&T UNIX Software Operation formed in preparation for spinoff of USL.
1989SVR4
UNIX System V Release 4 ships, unifying System V, BSD and Xenix. Installed base 1.2 million.
1990XPG3
X/Open launches XPG3 Brand. OSF/1 debuts. Plan 9 from Bell Labs ships.
1991Linux
UNIX System Laboratories (USL) becomes a company. Linus Torvalds commences Linux development. Solaris 1.0 debuts.
1992SVR4.2
USL releases UNIX System V Release 4.2 (Destiny). XPG4 Brand launched. Novell announces intent to acquire USL.
19934.4BSD
4.4BSD the final release from Berkeley. Novell acquires USL.
Late 1993SVR4.2MP
Novell transfers rights to the "UNIX" trademark and the Single UNIX Specification to X/Open. COSE initiative delivers "Spec 1170".
1994Single UNIX Spec
X/Open introduces the Single UNIX Specification (formerly Spec 1170), separating the trademark from any code stream.
1995UNIX 95
X/Open introduces the UNIX 95 branding programme. Novell sells UnixWare business line to SCO.
1996The Open Group
The Open Group forms as a merger of OSF and X/Open.
1997Version 2
Version 2 of the Single UNIX Specification is released, adding support for realtime, threads and 64-bit processors.
1998UNIX 98
The Open Group introduces the UNIX 98 family of brands (Base, Workstation, Server).
1999UNIX at 30
The UNIX system reaches its 30th anniversary. Joint development of a revision to POSIX and the Single UNIX Spec begins.
2001Version 3
Version 3 of the Single UNIX Specification unites IEEE POSIX, The Open Group and the industry efforts.
2003ISO/IEC 9945:2003
The core volumes of Version 3 are approved as an international standard.
2007Mac OS X Certified
Apple Mac OS X is certified to UNIX 03.
2008ISO/IEC 9945:2008
The latest revision of the UNIX API set is formally standardized at ISO/IEC, IEEE and The Open Group.
2009UNIX at 40
IDC reports the UNIX market at $69 billion in 2008, predicting $74 billion in 2013.
2010Desktop Dominance
Apple reports 50 million desktops and growing—all Certified UNIX systems.
2015Version 4
The Single UNIX Specification Version 4 (SUSv4) is published, forming the basis for the UNIX V7 Certification program.
2018First UNIX V7 Cert
Oracle Solaris 11.4 becomes the first product to be certified as conforming to the latest UNIX V7 standard.
2019UNIX at 50
Happy 50th Birthday, UNIX!
2020IBM certifies AIX to the UNIX V7 standard
Increased reliance on POSIX and UNIX systems during the shift to remote working during the pandemic.
2022Apple certifies macOS 12 Monterey
Apple continues its long-standing commitment by certifying its annual release for the 15th year. Estimated sales of Mac computers exceed 200 million units.
202425 Years of the Austin Group
25 years of joint development of the POSIX and Single UNIX Spec. The Single UNIX Specification Version 5 (SUSv4) is published.
2025Apple certifies the macOS Tahoe release
macOS continues as the largest installed base of any certified UNIX platform - estimated at tens of millions of active systems.

A Spec with No Name

How a cowboy legend helped unify the UNIX world.

The Problem: Fragmentation

In the early 1990s, major vendors like Sun, HP, and IBM had developed incompatible versions of UNIX, making it hard for software to be portable across platforms.

A Spec with No Name

A unified standard was needed, but the effort was politically sensitive. As a result, it was informally called "The Spec with No Name," later known as Spec 1170.

Enter: Eastwood

To ensure vendors implemented the spec correctly, a conformance test suite was nicknamed "Eastwood"— an inside joke referencing Clint Eastwood’s character, “The Man with No Name.”

A Lasting Legacy

This effort laid the foundation for The Single UNIX Specification and was a key part of the UNIX brand consolidation.

"This is the Unix philosophy: Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface."


An Enduring Legacy

While the corporate battles have faded, the core philosophy and UNIX technical innovations are more relevant than ever. They form the bedrock of nearly all modern computing, from the servers that run the internet (Linux), to the phones in our pockets (Android/iOS), to the computers on our desks (macOS, Windows Subsystem for Linux).