View source for UNIX Fourth Edition

{{Infobox OS 
| name = Unix V4
| creator = AT&T/[[Western Electric]]
| year introduced = November, 1973
| previous version = [[UNIX Third Edition|V3]]
| current version = V4
| next version = [[UNIX Fifth Edition|V5]]
| type = [[Multi-tasking]], [[multi-user]]
| architecture = [[PDP-11 architecture|PDP-11]]
}}

'''UNIX Fourth Edition''' (often referred to as '''UNIX V4''' or '''V4 UNIX''' - 'Unix' was still normally given in all capital letters at this point in time) was an important early version of [[UNIX]]. It was the first version in which the [[kernel]] was written in [[C programming language|C]]. It also had minor changes to the [[UNIX file system‎]] (such as the ability of any [[inode]] to hold a [[peripheral|device]] 'special file'), which left it in the form it retained until the [[BSD Fast File System]].

Apparently, the only model of PDP-11 supported was the [[PDP-11/45]].

A complete copy of Fourth Edition does not seem to be extant. [[The Unix Heritage Society|TUHS]] has a copy of the 'UNIX Programmer's Manual' and the [[source]] for what would become the V4 kernel. The main differences in this 'nsys' kernel compared to the later V4 kernel are the earlier V3 way of registering signal handlers, and a few not yet implemented system calls. Most importantly [[pipe]]s had not yet been implemented, making this kernel not fully functional even on a V3 system.

==External links==

* [https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4 V4]
** [https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/nsys nsys] - complete kernel source
** [https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/man/man0/intro UNIX Programmer's Manual Fourth Edition - Introduction]
** [https://minnie.tuhs.org/cgi-bin/utree.pl?file=V4/man/man5/fs.5 File system]
* [http://squoze.net/UNIX/v4man/ UNIX Programmer's Manual: Fourth Edition]

{{Nav Unix}}

[[Category: PDP-11 Operating Systems]]
[[Category: Non-DEC Operating Systems]]
[[Category: Unix OS's]]