History of UNIX

UNIX is an operating system that originated over forty years ago in 1969. It has been developing ever since.

In the sixties, computers were large and very expensive. People did not sit at them and use them as we do now. Data about transactions were typed onto paper tape or cards or magnetic tape, or later disks, and then processed in batches, all at once. This was a very efficient way to use the computer whose use was priced in pounds per minute, and was fine for payroll, stock updates, and accounts. The main processor was in a locked air-conditioned room. The people punching tape or cards worked separately. Even when people used connected screens to type in batch data they were not sitting at computers but 'dumb terminals', in the American sense of dumb meaning stupid. When they pressed a key the data from the key-presses went to the central processor and then back to their screens. Everything was under tight control.

Batch processing was no good for scientists, programmers and designers, who would type up their work then wait their turn for hours or days for their data to be processed. They needed to be connected to the computer interactively, so they could get an immediate response when they typed something in. Using computers in this way is dangerous. It allows people to change real live data, possibly including data that is not theirs. Operating systems for interactive multi-user systems have to know who is using the computer and make sure that data is secure. It must have networking built into it and ensure that one user does not hog the computer resources.

Scientists at Bell Labs, the research branch of AT&T, wanted interactive processing. Ken Thompson developed an operating system called UNIX. This allowed multiple users, data security and communication between users. Dennis Ritchie rewrote it in C. It had two overwhelming other advantages. First because it was written in C, it could be installed on ('ported to') any suitable computer. It wasn't tied to one make or model like existing operating systems, and it became the default operating system for the new cheaper mini-computers like the PDP-11. Secondly it could be adapted by users for their own needs. A wide range of user-interface shells emerged, including a general purpose Bourne shell, bash, from Berkeley and a C shell for programmers. The UNIX world is laid back and playful. Experts are known as gurus and there are plenty of puns, as in bash (bourne again shell) and C shell.

In the 1980s IBM type personal computers (PCs) became powerful enough to run UNIX. One machine might have three or four terminals attached, but UNIX systems still needed expertise to set up and run and the software was expensive, that is until GNU took it on.


The GNU Project was set up in 1984 by Richard Stallman at MIT to create a free operating system to replace UNIX. Linus Torvalds took on the job of writing a totally new UNIX kernel that would be open source and free. The GNU operating system, the linux kernel and the X window user interface were combined to produce what we now call linux but is more correctly called GNU/linux. GNU is short for GNU's Not Unix. This is a typical pun of the UNIX world as GNU is recursive in that it contains itself.

GNU/linux systems still needed a guru even after the introduction of the X window interface. Enter ubuntu.


(C) Peter Scott 2013

Last edit 26 December 2015