Ninth Edition Unix, also known as Version 9 Unix or V9, was a version of the Research Unix

Research Unix

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 ....

 operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

 developed and used internally at the Bell Labs

Bell Labs

Bell Laboratories is the research and development subsidiary of the French-owned Alcatel-Lucent and previously of the American Telephone & Telegraph Company , half-owned through its Western Electric manufacturing subsidiary.Bell Laboratories operates its...

 Information Sciences Research Division, "released" in September 1986. V9 was the successor to V8

Version 8 Unix

Eighth Edition Unix, also known as Version 8 Unix or V8, was a version of the Research Unix operating system developed and used internally at Bell Labs and a select number of universities. It was "released" in February 1985, ran on VAX hardware, and was a variant of 4.1cBSD with some System V.1 ...

, and the predecessor to the last Research Unix version, V10

Version 10 Unix

Tenth Edition Unix, also known as Version 10 Unix or V10, was the last version of the Research Unix operating system developed and used internally at Bell Labs. "Released" in 1989, it was the successor of V9...

. It was based on 4.3BSD, and featured a generalized version of the STREAMS

STREAMS

In computer networking, STREAMS is the native framework in Unix System V for implementing character devices.STREAMS was designed as a modular architecture for implementing full-duplex I/O between kernel or user space processes and device drivers. Its most frequent uses have been in developing...

 IPC mechanism introduced in V8. http://cm.bell-labs.com/cm/cs/who/dmr/ipcpaper.html

The book The AWK Programming Language was prepared on a VAX 8650

VAX 8000

The VAX 8000 was a family of minicomputers developed and manufactured by Digital Equipment Corporation using processors implementing the VAX instruction set architecture .- VAX 8600 :...

running Ninth Edition Unix.