UNIX Chronology

"The success of the UNIX system stems from its tasteful selection of a few key ideas and their elegant implementation. The model of the UNIX system has led a generation of software designers to new ways of thinking about programming. The genius of the UNIX system is its framework, which enables programmers to stand on the work of others."

Citation from the 1983 ACM Turing Award presented to Kenneth Thompson and Dennis Ritchie

"The Swiss Army Knife of Software."
"Some consider UNIX to be the second most important invention to come out of AT&T Bell Labs after the transistor."
"UNIX is simple and coherent, but it takes a genius (or at any rate a programmer) to understand and appreciate the simplicity."

Dennis Ritchie

A nice timeline diagram, showing the evolution of the various Unix variants, is available at Éric Lévénez's UNIX History.


The Antitrust Department of the Department of Justice of the US Government sues Western Electric and AT&T for restraint of trade. Western Electric was a wholly owned subsidiary of AT&T and that Bell Telephone Laboratories (BTL or Bell Labs) was jointly owned by Western Electric and AT&T (50% each). The consent decree required that AT&T license use of all its patents at nominal fees, which laid the groundwork for subsequent licensing of UNIX to universities.


AT&T enters into "consent decree" with US government and agrees to restrict its business to furnishing "common carrier communications services", which keeps it out of the computer business.


Bill Norris starts Control Data Corporation (CDC).


AT&T, GE, IBM and Project MAC at MIT join together to develop the time-sharing system MULTICS (Multiplexed Information and Computing Service).


Ken Thompson finishes studies at University of California at Berkeley (UCB) and joins technical staff at AT&T Bell Telephone Laboratories to work on MULTICS.


Dennis Ritchie completes work on his doctorate at Harvard and joins Bell Labs to work on MULTICS project.


AT&T Bell Labs drops out of MULTICS project. A system which was supposed to support 1000 on line users can barely handle three. Out of the ashes grows the most influential operating system in history.

Thompson gets an idea for a new type of file system and hashes out his ideas with Ritchie and Rudd Canaday.

Thompson writes first version of UNICS for PDP-7 in one month while wife is on vacation. He allocates one week each to the operating system functions: the kernel, the shell, the editor, and the assembler. He does this on a machine with 4K of 18 bit words. UNICS is pun on MULTICS and stands for Uniplexed Information and Computing Services. Name is changed to UNIX which is not an acronym. This version is in assembly language.

Thompson develops the interpretive language B based upon BCPL. Ritchie improved on "B" and called it "C"


DEC begins shipping PDP-11 and revolutionizes the computer industry by selling 250,000 systems.

Bell Labs gets a PDP-11 to do text processing for the legal department. System is developed and implemented in UNIX. The standard DEC OS is never installed.


The First Edition of UNIX manual is written.


UNIX OS is rewritten in C which opened the door for porting.


First UNIX development support group is formed in Bell Labs.

Pipes are invented with the Third Edition of UNIX and the UNIX philosophy begins to emerge:

Thompson delivers first UNIX paper at the ACM Symposium on Operating Systems at the Thomas J. Watson Research Center in Yorktown Heights, NY. Within six months, the number of UNIX sites triples from 16 to 48.


The UNIX Time-Sharing System is published in CACM by Ken Thompson and Dennis Ritchie. It is a revision of the 1973 paper.

University of California at Berkeley (UCB) gets Version 4 of UNIX.

Keith Standiford converts UNIX to PDP 11/45.

Berkeley begins making major enhancements to UNIX and sets the stage for becoming a major distribution center for their version of UNIX.

The Elements of Programming Style by Kernighan and Plauger is published.


Thompson begins one year sabbatical at Berkeley.

AT&T officially begins licensing UNIX to universities.


Boggs and Metcalfe invent Ethernet at Xerox in Palo Alto.


Bill Joy produces first Berkeley Software Distribution (BSD) of UNIX.

Ritchie and Steve Johnson complete first port of UNIX to an Interdata 8/32, the first non-DEC computer to run UNIX. Note that this is nearly ten years after running only on DEC equipment.

UNIX is ported to a DEC VAX, but not by Thompson and Ritchie, since they had become disenchanted by DEC and its unwillingness to support UNIX. DEC's refusal to support UNIX must be one of the all time great blunders of the computer industry.

The C Programming Language by Kernighan and Ritchie is published.

Doug and Larry Michels start Santa Cruz Operations, Inc. (SCO) to sell UNIX on a PC. By 1992, they grow to $175 million in revenues.


Seventh Edition UNIX PROGRAMMERS MANUAL (UNIX Version 7) is published. It is the first edition without Thompson's or Ritchie's names. It is titled "UNIX (with a TM sign) Time-Sharing System." Bell Labs starts to protect its assets.

Microsoft licenses UNIX from AT&T and announces XENIX, which is soon overshadowed by MS-DOS.


BSD UNIX finds its way back into Bell Labs as a new improved version.

Berkeley lands large DARPA contract and forms Computer Systems Research Group (CSRG).

SCO becomes a distributor for Microsoft XENIX and licenses the name XENIX because they sold their trade name DYNIX to Sequent.


The IBM PC is released running Microsoft DOS; XENIX is pushed into the background.


AT&T announces official support for UNIX and makes its first commercial release: UNIX System III.

Bill Joy, the inspiration behind BSD, leaves CSRG at Berkeley to co-found Sun Microsystems.

Sun gets its name from the Stanford University Network (SUN) board. The workstation is based on the Motorola 68000 chip running SunOS based on 4.2BSD. It includes an optional local area network based on Ethernet. The commercial UNIX industry is in full gear.

HP announces support for UNIX on its 9000 workstations.

DEC releases ULTRIX.

IBM releases CPIX.


Thompson and Ritchie receive ACM Turing award for their work on UNIX.

Richard Stallman, creator of EMACS and the Lisp Machine, starts GNU at MIT. First GPL.


AT&T agrees to divest itself of the Bell Operating Companies and obtains the right to enter the computer business.

Fortune runs an article saying that 750 universities around the world, about 80% of those offering computer science degrees, have UNIX licenses.

X/Open is formed, by five European computer manufacturers: Bull, ICL, Siemens, Olivetti, and Nixdorf. The press refers to them as BISON.

Andrew Tanenbaum writes the first version of Minix, a Unix intended for educational purposes.

Apple releases the Macintosh.


AT&T publishes the System V Interface Definition (SVID) in an attempt to standardize the UNIX interfaces, which was strongly influenced by the 1984 /usr/group standard.

The ISO introduced the POSIX standard.


IBM releases AIX.


AT&T BUYS 20% OF SUN MICROSYSTEMS, and the battle lines are formed.

IBM, DEC, HP, and others form Open Software Foundation (OSF) to compete with the AT&T/Sun alliance. They decide to use the AIX Kernel.

UNIX International (UI) is formed in response to OSF as an international consortium of System V UNIX users to work closely with AT&T to promote open systems and influence future development.

NeXT computer selects Mach Kernel for its NeXTStep OS.

David Cutler leaves DEC and joins Microsoft (October 31) to develop Windows NT.

Microsoft begins evaluating the Mach Kernel.

HP releases HP/UX.


The C programming language is standardized by ANSI as X3.159.1989 which became an international standard ISO/IEC 9899:1990.

HP becomes the second largest supplier of UNIX based workstations by acquiring Apollo.

SCO is short of cash, and Microsoft, along with other investors, puts $25 million into SCO in exchange for 16% of the stock.


OSF designates the Mach 3.0 Kernel from Carnegie-Mellon University as their choice for their version of UNIX, OSF/1.

Motif is released by OSF.

UNIX International releases SVR4 which is a unification of System V, BSD, and XENIX.

X/Open releases XPG3.


AT&T incorporates UNIX System Laboratories (USL) with Novell, Amdahl, Fujitsu, Sun, Motorola, ICL, Olivetti, NEC, OKI Electric, III of Taiwan, and Toshiba.

Sun creates the SunSoft subsidiary and announces Solaris.

A finnish student at the University of Helsinki, Linus Torvalds, learns of Minix, and writes a kernel based on it. Linux 0.01 goes on the net under GPL. Instantly, he started receiving patches and enhancements.

GNU begins work on HURD, based on Mach 3.


BSDI (Berkeley Software Design, Inc.) is formed and releases BSD/386, a PC version of UNIX, including source, for the low price of $995.

BSDI is sued by USL.

AT&T sells its ownership interest in Sun.

DEC introduces Alpha AXP, its 64 bit RISC processor.

Peter McDonald compiles the first Linux distribution, the SLS (Soft Landing Software).


UNIX International (UI) terminates business.

4.4BSD is released.

In April, Patrick Volkerding compiles the Slackware distribution, based on SLS.

Novell buys USL from AT&T in June.

Novell gives the UNIX brand and trademark to X/Open in October.

The Common Open Software Environment (COSE) is created at UniForum.

Microsoft releases Windows NT.

The Common Desktop Environment (CDE) is demonstrated.

Linux is ported to non-Intel platforms (MIPS, Alpha,...).

FreeBSD and NetBSD are released, under the BSD licence.


A settlement is reached between USL and BSDI. 4.4BSD-Lite is released at Berkeley. It differs from the previous version for just three files among 18,000.

SunSoft, AT&T GIS, Novell, and Fujitsu pay $1 million to join OSF. This is primarily in recognition of the threat from Microsoft and the need to further standardize.

RedHat is founded.

Linux 1.0 is released.

First Beowulf cluster at NASA.


4.4BSD-Lite Release 2 is released and CSRG is disbanded at Berkeley (June 1995). Now both Berkeley and AT&T are out of the UNIX development business.

X/Open releases the UNIX95 brand. A UNIX95 products must conform in four areas:

Explosion of the World Wide Web.


X/OPEN and OSF merge, founding the Open Group.

MkLinux, Linux on Mach microkernel, is released.

Linux 2.0 is released.


The Single Unix Specification, V2, is released.

Linux becomes the operating system of choice of ISP.

Windows NT share in industry is arising, at the expense of UNIX.


The UNIX98 brand is released. It comprises three categories of UNIX: base, workstation, server.

Compaq buys DEC.

The Open Source movement get momentum. The press discovers Linux and the Open Source movement. Torvalds appears on Forbes.

Oracle, Informix, IBM, Compaq and others announce support for Linux.

Netscape goes open source with the name Mozilla.


Industry is getting interested in Linux. Renewed interested in UNIX products.

Major commercial software developers begin to release versions for Linux. SAP announces SAP/R3 for Linux.

Apple releases Mac OS X, based on Mach, and begins the Darwin project.

SCO, IBM, Sequent and Intel join in the Monterey Project, whose goal "is to deliver a single UNIX system product line consisting of UnixWare 7 (on the Intel IA-32 architecture), AIX (on the IBM Power architecture), and Monterey/64 (on the Intel IA-64 architecture)."

Sun incorporates StarDivision, and start to distribute part of Solaris sources under the Sun Community Licence.

Microsoft is ruled of monopoly in the market for personal computers.


Major commercial hardware vendors (Compaq, IBM, Dell, SGI, Fujitsu) begin to sell desktop and laptop computers with Linux pre-installed.

Sun releases Solaris 8 sources under the Foundation Source code license.

Microsoft is condemned to be split in two companies.

Linux is ported to the IBM S/390.

Lockheed Martin Corp. is using Linux NetworX's cluster technology to analyze U.S. Navy aircraft.

Sun announces that it will release the source code for its Star Office suite

Sun announces that it will join the GNOME project, and to adopt the GNOME environment on its workstations in place of CDE.

IBM invests more than $200 million in a series of Linux initiatives in Europe over the next four years.

IBM and RedHat will develop versions of Linux native for all IBM platforms (AS/400, RS/6000, S390 and Netfinity). The IBM Application Developer Kit will be ported to Linux.

IBM announces AIX 5L, one of the few results of the Monterey project.

Caldera acquires UnixWare, the Server Software Division and the Professional Services Division from SCO. SCO will retain its Tarantella Division. Linux will be available on UnixWare as the Linux Kernel Personality.

Many firms of the new economy are in financial troubles.

Sun starts to distribute the UltraSPARC III.

Sun acquires Cobalt Networks, which builds Linux-based servers.

Apple distributes MacOS X client, based on FreeBSD and Mach microkernel.

HP releases HP-UX 11i, a full 64 bit Unix which will be compatible with Linux.

SAP releases the famous ERP SAP/R3 as Open Source.


Linux 2.4 is released.

Sony announces a porting of Linux to the PlayStation 2.

Sun launches the JXTA project, an open source protocol allowing peer-to-peer communication and distributed computing between any peers that are recognized on the network.

IBM presents AIX 5L, as a result of the Project Monterey. It is compatible with Linux.

Microsoft attacks the GNU Public Licence, claiming that it cannot protect the intellectual property of private and public software houses. But even the Software & Information Industry Association (SIIA) criticizes Microsoft on this, saying that "Microsoft is once again publicly making the case that innovation in the software industry should happen only at the discretion and direction of Microsoft, [...] Microsoft is employing public relations tactics to incite fear among businesses that are considering migrating to the Open Source model."

IDC forecasts in the U.S. Multiuser System Market by 2004:
OS 1999 2004 difference
Unix $11.4 billion $14.9 billion +30%
Windows NT $4.7 billion $12.8 billion +172%
Linux $367 million $4.1 billion +1017%

Nokia adopts Linux to develop applications for its Media Terminal home entertainment system.

HP adopts Debian as the selected development platform for Linux work at HP.

IBM announces a new supercluster running Linux, installed at the National Center for Supercomputing Applications (NCSA). Capable of 1 trillion calculations per second, the cluster of 160 new IBM Itanium-based systems will be the most powerful Linux supercluster in academia.

Fujitsu, Hitachi, IBM, and NEC announce a partnership "to refine features needed to drive Linux further into the enterprise", working together with the Linux community to develop various open source projects.

Microsoft releases Office X, the porting of the Office suite to MacOS X - which is, ultimately, a Unix variant.


The Free Standards Group released LSB 1.1 (including a full set of common APIs and a development package), and Li18nux (an internationalization guide), two tools intended to ensure that all Linux applications can run on any Linux Standard Base-compliant version.

After the acquisition of Cobalt, Sun embraces aggressively the Linux operating system with a multipart program that will significantly broaden the offerings of Linux on low-end Sun servers and workstations and commit new resources to the ongoing development of the Open Source operating system.

IBM adopts Red Hat Linux Advanced Server for all servers and mainframes.

Part of the content of this page is taken from a talk by John Kelly. Thanks to the many that pointed out errors. Comments are welcome.
Marino Miculan
Last modified: Mon Jan 27 09:06:20 CET 2003