Research Unix refers to early 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 Sciences Research Center (CSRC).
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.
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, 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 Version x (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.
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, which also included some BSD code:
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 operating system was two years old, having been ported from the PDP-7 to the PDP-11/20 in 1970. Includes ar, as, bcd, cal, cat, chdir, chmod, chown, cmp, cp, date, dc, df, du, ed, find, glob, init, ld, ln, ls, mail, mesg, mkdir, mkfs, mount, mv, nm, od, pr, rm, rmdir, roff, sh, sort, stat, strip, su, sum, tty, umount, wc, who, write; also precursors of fsck, reboot, and adb. The system also had a B and Fortran compiler, a BASIC interpreter, device files and functions for managing punched tape, DECtape, and RK05 disks.|
|2nd Edition||Jun. 12, 1972||Total number of installations at the time was 10, "with more expected", according to the preface of the manual.:ii Adds echo, exit, login, m6 macro processor, man, nroff, strip, stty, tmg compiler-compiler and the first C compiler.|
|3rd Edition||Feb. 1973||Introduced a C debugger, pipes, crypt, kill, passwd, ps, size, speak, split, uniq, and yacc. Commands are split between |
|4th Edition||Nov. 1973||First version written in C. Also introduced comm, dump, file, grep, nice, nohup, sleep, sync, tr, wait, and printf(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, the first public exposition of the operating system.|
|5th Edition||Jun. 1974||Widely licensed to educational institutions. Introduced col, dd, diff, eqn, lpr, pwd, spell, tee,  and the sticky bit. Targeted the PDP-11/40 and other 11 models with 18 bit addresses. Installations "above 50".|
|6th Edition||May 1975||Includes ratfor, bc, chgrp, cron, newgrp, ptrace(2), tbl, units, and wall. First version widely available outside of Bell Laboratories, licensed to commercial users, 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.|
|7th Edition||Jan. 1979||Includes the Bourne shell, ioctl(2), stdio(3), and pcc augmenting the Dennis Ritchie's C compiler. Adds adb, at, awk, banner, basename, cu, diff3, expr, f77, factor, fortune, iostat, join, lex, lint, look, m4, make, rev, sed, tabs, tail, tar, test, touch, true, false, tsort, uucp, uux. The ancestor of UNIX System III 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. Ported to PDP-11, Interdata 8/32 and VAX (UNIX/32V). 32V was the basis for 3BSD.|
|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. Adds Berkeley DB, curses(3), cflow, clear, compress, cpio, cut, ksh, last, netstat, netnews, seq, telnet, tset, ul, vi, vmstat. The Blit graphics terminal became the primary user interface. Includes Lisp, Pascal and Altran. Added a network file system that allowed accessing remote computers' files as |
|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 user space. Other innovations include Sam. According to Dennis Ritchie, V9 and V10 were "conceptual": manuals existed, but no OS distributions "in complete and coherent form".|
|10th Edition||Oct. 1989||Last Research Unix. Although the manual was published outside of AT&T by Saunders College Publishing, there was no full distribution of the system itself. 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 Doug McIlroy and James A. Reeds' multilevel-secure operating system IX.|
|Plan 9 1st Edition||1992||Plan 9 was a successor operating system to Research Unix developed by Bell Laboratories Computing Science Research Center (CSRC).|
In 2017, Unix Heritage Society and Alcatel-Lucent USA Inc., on behalf of itself and Nokia Bell 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.