The term Research Unix first appeared in the Bell System Technical Journal (Vol. 57, No. 6, Part 2 July/August 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.
AT&T licensed Version 5 to educational institutions, and Version 6 also to commercial sites. Schools paid $200 and others $20,000, discouraging most commercial use, but Version 6 was the most widely used version into the 1980s. Research Unix versions are often referred to by the edition of the manual that describes them,[1] because early versions and the last few were never officially released outside of Bell Labs, and grew organically. So, the first Research Unix would be the First Edition, and the last the Tenth Edition. Another common way of referring to them is as "Version x Unix" or "Vx Unix", where x is the manual edition. All modern editions of Unix—excepting Unix-like implementations such as Coherent, Minix, and Linux—derive from the 7th Edition.[citation needed]
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,[2] which also included some BSD code:[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.
Introduced a C debugger, pipes, crypt, kill, passwd, ps, size, speak, split, uniq, and yacc. Commands are split between /bin and /usr/bin, requiring a search path[3] (/usr was the mount point for a second hard disk). Total number of installations was 16.
4th Edition
Nov 1973
First version written in C. Also introduced comm, dump, file, grep, nice, nohup, sleep, sync, tr, wait, and printf(3).[3] Included a SNOBOL interpreter. Number of installations was listed as "above 20". The manual was formatted with troff for the first time. Version described in Thompson and Ritchie's CACM paper,[5] the first public exposition of the operating system.[3]
5th Edition
Jun 1974
Licensed to selected educational institutions.[1] Introduced col, dd, diff, eqn, lpr, pwd, spell, tee, [3] and the sticky bit. Targeted the PDP-11/40 and other 11 models with 18 bit addresses. Installations "above 50".
Includes ratfor, bc, chgrp, cron, newgrp, ptrace(2), tbl, units, and wall.[3] First version widely available outside of Bell Laboratories, licensed to commercial users,[1] and to be ported to non-PDP hardware (Interdata 7/32). May 1977 saw the release of MINI-UNIX, a "cut down" v6 for the low-end PDP-11/10.
Incorporated code from 4.3BSD; used internally. Featured a generalized version of the StreamsIPC 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 user space.[9] Other innovations include Sam.[3] According to Dennis Ritchie, V9 and V10 were "conceptual": manuals existed, but no OS distributions "in complete and coherent form".[6]
10th Edition
Oct 1989
Last Research Unix. Although the manual was published outside of AT&T by Saunders College Publishing,[10] there was no full distribution of the system itself.[6] Novelties included graphics typesetting tools designed to work with troff, a Cinterpreter, animation programs, and several tools later found in Plan 9: the Mk build tool and the rc shell. V10 was also the basis for Doug McIlroy and James A. Reeds' multilevel-secure operating system IX.[11]
In 2017, Unix Heritage Society and Alcatel-Lucent USA Inc., on behalf of itself and NokiaBell Laboratories, released V8, V9, and V10 under the condition that only non-commercial use was allowed, and that they would not assert copyright claims against such use.[16]