Research Unix

研究 Unix，是一系列的Unix作業系統的通稱，由貝爾實驗室的計算機科學研究中心（Computing Science Research Center，部門編號1127）研發，因此得名，共有11個版本。這些Unix系統運行在DEC PDP-7，PDP-11，VAX，以及Interdata 7/32與8/32電腦上。

版本

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. Includes the Thompson shell, mail, cp, and su. The operating system was two years old, having 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. Includes echo and the first C compiler.
3rd Edition	Feb. 1973	Introduced the C programming language, pipes, crypt, and yacc. Commands are split between /bin and /usr/bin, requiring a search path (/usr was the mountpoint for a second hard disk). Total number of installations was 16.
4th Edition	Nov. 1973	First version written in C. Also introduced groups, grep, and printf. 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 find, dd, 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 and bc. First version to be also licensed to commercial users, and 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	Includes the Bourne shell, cpio, sed, ioctl, awk, f77, spell, and stdio. 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. The Blit graphics terminal became the primary user interface. 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. First version with no assembly in the documentation.
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. Other innovations include make and 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.