---
keywords: ["nsys", "Unix v4", "Unix", "PDP-11", 1970s, 1973]
image: ./nsys.webp
description: "! Unix v4 was an operating system for the DEC PDP-11 computer. It was developed by Bell Labs."
sidebar_position: 2
---

import DocCardList from '@theme/DocCardList';

# ! Unix v4

![! Unix v4](./nsys.webp)

! 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:

- [! Unix Programmer's Manual, 3rd Edition](https://dspinellis.github.io/unix-v3man/v3man.pdf)
- [! Unix Programmer's Manual, 4th Edition](https://dspinellis.github.io/unix-v4man/v4man.pdf)
- [! Unix Programmer's Manual, 5th Edition](https://www.tuhs.org/Archive/Distributions/Research/Dennis_v5/v5man.pdf)

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:

- [PDP-11 Manuals](http://bitsavers.org/pdf/dec/pdp11/)

## Related Pages

- [VirtualHub Screenshots](https://screenshots.virtualhub.eu.org/1970s/1973/unix-v4/)
- [Wikipedia](https://en.wikipedia.org/wiki/History_of_Unix#1970s)
- [Computer History Wiki ! Unix v3 page](https://gunkies.org/wiki/UNIX_Third_Edition)
- [Computer History Wiki ! Unix v4 page](https://gunkies.org/wiki/UNIX_Fourth_Edition)
- [Computer History Wiki ! Unix v5 page](https://gunkies.org/wiki/UNIX_Fifth_Edition)
- [Computer History Wiki PDP-11 page](https://gunkies.org/wiki/PDP-11)

## Credits

- ! Unix v3 and v4 manuals were taken from the page of the GitHub user "[dspinellis](https://github.com/dspinellis)".
- The rest of the manuals were taken from [The Unix Heritage Society (TUHS)](https://www.tuhs.org) and [Bitsavers](http://bitsavers.org).