UNIX

UNIX
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:

• Unix "version 0" for PDP-7
• UNIX V1 - The first version of UNIX that has been recently made to run on the PDP-11
• UNIX V2 - Unclear changes
• UNIX V3 - The first version with pipes
• UNIX V4 - The first version with the kernel written in C
• UNIX V5 - The first version with complete source and binaries available
• UNIX V6 - The first widely distributed version; the last before branches started to appear
• Unix V7 - One of the most complete, and the last generally available and PDP-11 version of Research UNIX
• Unix/32V - A port of Seventh Edition to the VAX-11/780
• Unix Eighth Edition - this, and later versions, never contemporaneously escaped from Bell Labs
• Unix Ninth Edition
• Unix Tenth Edition

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.)

• UNIX System III
• UNIX System V
• Unix SYSVr2
• Unix SYSVr3
• Unix SYSVr4

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

• Brian Kernighan, UNIX: A History and a Memoir - Kernighan's memoir of UNIX and Bell Labs

See also

• Unix OS's
• Unix-based OS's
• UNIX file system
• Repairing early UNIX file systems
• BSD Fast File System
• Unix dump/restore tape format

External links

• The Unix Heritage Society
  • The Unix Tree - Complete source for many early versions of Unix
  • Dennis Tapes - images of some dusty DECtapes Dennis found
• The Unix Heritage Wiki
• Dennis M. Ritchie - see section "Unix papers and writings, approximately chronological"
  • The UNIX Time-Sharing System - the slightly later BSTJ version
    • The UNIX Time-Sharing System - the classic original CACM paper that ignited the spread outside Bell (PDF, but not a scan)
  • The Evolution of the Unix Time-sharing System
  • The UNIX Time-sharing System - A Retrospective
• UNIX Implementation - a Thompson paper giving an overview of the kernel
• The UNIX I/O System - a Ritchie document covering part of the same ground in more detail
• The UNIX Operating System
  • A History of UNIX before Berkeley: UNIX Evolution: 1975-1984
  • A Research UNIX Reader
• An Oral History of Unix - Lengthy interviews with Thompson, Ritchie, McIlroy, etc
• bltj - the second BSTJ issue on UNIX
  • The UNIX System: Preface
  • The UNIX System: Foreword
  • Multiprocessor UNIX Operating Systems
  • The Evolution of UNIX System Performance
  • A Stream Input-Output System
• Papers about Unix Portability
  • Portability of C Programs and the UNIX System - the 8/32 port
• On the Early History and Impact of Unix: Tools to Build the Tools for a New Millenium
• The Berkeley Software Distribution - covers the early period, too
• Inter-UNIX Portability - mostly about the commands
• The Restoration of Early UNIX Artifacts
• Unix and Multics

Fun links

• The Unix Power Classic: A book about the Unix Way and its power - Hacker-oriented version of the Dao De Jing
• Rootless Root: The Unix Koans of Master Foo