Research Unix

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Research Unix is a term used to refer to versions of the Unix operating system for DEC PDP-7, PDP-11, VAX and Interdata 7/32 and 8/32 computers, developed in the Bell Labs Computing Science Research Center (frequently referred to as Department 1127).


Version 7 Unix for the PDP-11, running in SIMH

The term Research Unix first appeared in the Bell System Technical Journal (Vol. 57, No. 6, Pt. 2 Jul/Aug 1978) to distinguish it from other versions internal to Bell Labs (such as PWB/UNIX and MERT) whose code-base had diverged from the primary CSRC version. However, that term was little-used until Version 8 Unix, but has been retroactively applied to earlier versions as well. Prior to V8, the operating system was most commonly called simply UNIX (in caps) or the UNIX Time-Sharing System.

Because both the early versions and the last few were never officially released outside of Bell Labs, and grew rather organically, Research Unix versions are often referred to by the edition of the manual that describes them. So, the first Research Unix would be the First Edition, and the last the Tenth Edition. Another common way of referring to them is Version x (or Vx) Unix, where x is the manual edition.

All modern editions of Unix (excepting implementations from scratch like Coherent, Minix, and Linux, usually referred to as Unix-like) derive from the 7th Edition.

Starting with the 8th Edition, versions of Research Unix had a close relationship to BSD. This began by using 4.1cBSD as the basis for the 8th Edition. In a Usenet post from 2000, Dennis Ritchie described these later versions of Research Unix as being closer to BSD than they were to UNIX System V:[1]

Research Unix 8th Edition started from (I think) BSD 4.1c, but with enormous amounts scooped out and replaced by our own stuff. This continued with 9th and 10th. The ordinary user command-set was, I guess, a bit more BSD-flavored than SysVish, but it was pretty eclectic.


Manual Edition Release date Description
1st Edition Nov. 3, 1971 First edition of the Unix manual, based on the version that ran on the PDP-11 at the time. "The system was already well-developed before v1 appeared";[2] it was actually 2 years old at the time and had been ported from the PDP-7 to the PDP-11/20 in 1970.
2nd Edition Jun. 12, 1972 Total number of installations at the time was 10, "with more expected", according to the preface of the manual.[3]:ii
3rd Edition Feb. 1973 Introduced the C programming language and pipes; total number of installations was 16. Commands were split between /bin and /usr/bin, since the 256 KB hard disk of the development machine was full[2] (/usr was the mountpoint for a second hard disk).
4th Edition Nov. 1973 First Unix written in C. It also introduced groups. Number of installations was listed as "above 20". The manual was formatted with troff for the first time. This is the version described in Thompson and Ritchie's CACM paper,[4] the first public exposition of the operating system.[2]
5th Edition Jun. 1974 Introduced the sticky bit. Targeted the PDP-11/40 and other 11 models with 18 bit addresses. Installations "above 50".
6th Edition May 1975 First Unix to see widespread distribution outside Bell Labs, as well as the first to be ported to non-PDP hardware. May 1977 saw the release of MINI-UNIX, a "cut down" v6 for the low-end PDP-11/10.
7th Edition Jan. 1979 The ancestor of all modern UNIX systems and the last release of Research Unix to see widespread external distributions. Merged most of the utilities of PWB/UNIX with an extensively modified kernel with almost 80% more lines of code than V6. In February, a port called 32V was made to DEC's VAX hardware; 32V was the basis for 4BSD.
8th Edition Feb. 1985 A modified 4.1cBSD for the VAX, with a System V shell and sockets replaced by STREAMS; used internally, and only licensed for educational use.[5] The Blit graphics terminal became the primary user interface.[2] Added a network filesystem that allowed accessing remote computers' files as /n/hostname/path, and a regular expression library that introduced an API later mimicked by Henry Spencer's reimplementation.[6]
9th Edition Sep. 1986 Incorporated code from 4.3BSD; used internally. Featured a generalized version of the Streams IPC mechanism introduced in V8. The mount system call was extended to connect a stream to a file, the other end of which could be connected to a (user-level) program. This mechanism was used to implement network connection code in userspace.[7] Other innovations included the text editor, Sam.[2] According to Dennis Ritchie, V9 and V10 were "conceptual": manuals existed, but no OS distributions "in complete and coherent form".[5]
10th Edition Oct. 1989 Last Research Unix. Although the manual was published outside of AT&T by Saunders College Publishing,[8] there was no full distribution of the system itself.[5] Novelties included graphics typesetting tools designed to work with troff, a C interpreter, animation programs, and several tools later found in Plan 9: the Mk build tool and the rc shell. V10 was also the basis for Douglas McIlroy and James A. Reeds' multilevel-secure operating system IX.[9]

Version 3, Version 4 and Version 5 should not be confused with the UNIX 3.0, UNIX 4.0 and UNIX 5.0 releases by the AT&T UNIX Support Group. After Version 10, Unix development at Bell Labs was stopped in favor of a successor system, Plan 9 from Bell Labs, that shared part of its userland with V10.

See also[edit]


  1. ^ Dennis Ritchie (26 October 2000). "alt.folklore.computers: BSD (Dennis Ritchie)". Retrieved 3 July 2014. 
  2. ^ a b c d e M. D. McIlroy (1987). A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986. CSTR 139, Bell Labs.
  3. ^ UNIX Programmer's Manual, Second Edition. Bell Telephone Laboratories. June 12, 1972. 
  4. ^ D. M. Ritchie and K. Thompson (1974). The UNIX Time-Sharing System. CACM 17(7):365–375.
  5. ^ a b c Dennis Ritchie (27 June 2003). "[TUHS] Re: V7 UNIX on VAX 11/750". Retrieved 9 April 2014. 
  6. ^ Henry Spencer (1986-01-19). "regexp(3)". mod.sources. Web link. Retrieved 9 January, 2013.
  7. ^ David L. Presotto; Dennis M. Ritchie (1990). "Interprocess Communication in the Ninth Edition Unix System". Software—Practice and Experience 19. 
  8. ^ "Unix Tenth Edition Manual". Bell Labs. Retrieved 25 December 2013. 
  9. ^ "The IX Multilevel-Secure UNIX System". 

External links[edit]