UNIX Third Edition

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Unix V3
Type: Multi-tasking, multi-user
Creator: AT&T/Western Electric
Architecture: PDP-11
Previous Version: V2
This Version: V3
Next Version: V4
Date Released: February, 1973

UNIX Third Edition (often referred to as UNIX V3 or V3 UNIX - 'Unix' was still normally given in all capital letters at this point in time) was a significant early version of UNIX. It was the version in which pipes appeared, and the last version in which the kernel was written in assembly language.

It ran on the the PDP-11/45, but the PDP-11/20 model of the PDP-11 was apparently still supported (whether without the KS11 is unknown). The memory management mechanisms were more limited than those that came in with UNIX Fourth Edition. ("In the future the text segment will be write-protected and shared." (a.out (V))).

The file system apparently identical to the one in UNIX Second Edition; i.e. almost identical to the V6 one: the only major differences from the latter being that i) the free blocks are stored as a bit array, rather than a linked list, and ii) device 'special files' are indicated by inode numbers below 41. (not via a flag in the 'mode' word in the inode, as later).

A complete copy of Third Edition does not seem to be extant. TUHS has a copy of the 'UNIX Programmer's Manual Third Edition', and the source code for an early version of the first C compiler (C was just being defined at the point in time, although it first appeared in UNIX Second Edition).

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