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Type: Time-sharing
Creator: Ken Thompson, Dennis Ritchie and Douglas McIlroy at Bell Labs
Multitasking: Multi-tasking with swapping/paging (latter added in a later version)
Architecture: Originally PDP-7, then PDP-11; now cross-platform.
Date Released: 1969

Unix (officially trademarked as UNIX® - the documentation switched from using 'UNIX' to 'Unix' as of V7) is a computer operating system originally developed in the 1970s by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy.

It was a descendant of, and inspired by, the Berkeley Time-Sharing System (on which Thompson worked), and CTSS and Multics (on which all of them had worked, before Bell Labs withdrew from the Multics project).

Today's Unix systems are split into various branches, developed over time by AT&T as well as various commercial vendors and non-profit organizations. A number of clones of Unix, which share the interfaces, and 'look and feel', but no code, have also been produced; most notably, Linux.

Notable Bell versions

Versions of relevance for hobbyists include the initial versions from inside Bell Labs; it later spread more widely inside the Bell system, at the same time that it was starting to appear outside.

'Research' versions

Note that 'Version' in early UNIXes refers to the revision of the 'UNIX Programmer's Manual'; UNIX didn't really have coordinated distros before about V6:

Other AT&T versions

The rest of the Bell system, outside Bell Labs, soon found it useful, too, and a number of disparate versions, intended for different environments, appeared:

  • CB-UNIX - for use in control applications, including real-time systems
  • PWB/UNIX - used for production of other systems, in for computer center type usage
  • USG UNIX - a version for general use inside the Bell system
Unix ad

These were later unified, and Unix then went commercial and was sold outside AT&T, in a number of releases. (To the side is an early ad for AT&T UNIX.)

Bell also moved UNIX to the IBM System/370, as a 'supervisor' to user processes, under the TSS/370 Resident Supervisor; the result, UNIX/370, ran on a number of large System/370 machines at Bell.

Portable versions

Fairly early on, it became obvious that UNIX, and most of its commands and subsystems, being written in C, would be portable, relatively easily.

Portability was a little-recognized idea at the time; with a few exceptions (such as Multics), most operating systems were written in assembly language, which tied them irretrievably to a particular ISA. Indeed, portability was not a stated goal of the UNIX project at any point; it likely became one of strengths of UNIX purely by accident.

The first two projects to move UNIX to another machine started almost simultaneously, and in ignorance of each other: one was at Bell, to move UNIX to the Interdata 8/32; the other was at the University of Wollongong, to the similar Interdata 7/32. Issues with the Interdata 8/32 prevented that project from being a success, but it produced Unix Seventh Edition, the first portable version; that in turn was used for Unix/32V and UNIX/370.

CSRG releases

Meanwhile the Computer Systems Research Group‎ kept on releasing newer BSD UNIX's, mostly for the VAX, derived from 32V. These had wide distribution, and tremendous impact; they were a major step in UNIX's road to its current ubiquity.

Descended from there are several popular versions:

  • FreeBSD focuses on providing a system geared towards a single user.
  • NetBSD will run on a variety of 32-bit older systems from the VAX to the Amiga.
  • OpenBSD derived from the NetBSD project will run on all kinds of systems.

Further reading

See also

External links

Fun links