description: "! Unix v4 was an operating system for the DEC PDP-11 computer. It was developed by Bell Labs."
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# ! Unix v4
! Unix v4 was an operating system for the DEC PDP-11 computer. It was developed by Bell Labs. Sadly, we do not have a complete copy of Unix v4, but we do have a copy of a [kernel](<https://en.wikipedia.org/wiki/Kernel_(operating_system)>) that is from between v3 and v4. We can use that kernel with v5 [userland](https://en.wikipedia.org/wiki/User_space). It can be used on SIMH PDP-11 emulator.
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## Manuals
Since the kernel is from between v3 and v4, and we use the userland of v5, here are the manuals of all of them:
Reading the volume 2A and 2B of ! Unix v7 manual is also helpful. They contain many short tutorials which will be helpful in learning how to use Unix. While the manual is for v7, most of the information included there applies to every version of Unix.
You may also be interested in the PDP-11 manuals. It was the computer on which ! Unix v3, v4 as well as v5 was supposed to run. You can download them from Bitsavers:
- The rest of the manuals were taken from [http://squoze.net](http://squoze.net/), [this page from Bell Labs](https://s3.amazonaws.com/plan9-bell-labs/7thEdMan/bswv7.html) and [Bitsavers](http://bitsavers.org).
