Scientists and engineers who worked on the UK’s pioneering Atlas computer together with many of its end users gathered in Manchester this week to celebrate its 50th anniversary. 

Sir John Cockcroft switches on Atlas at Manchester University on December 7th, 1962. Sebastian de Ferranti (left) and
Tom Kilburn (right) look on.

The first production Atlas was inaugurated at Manchester University on 7th December 1962 by Sir John Cockcroft, the Nobel prize-winning physicist who was Director of the UK’s Atomic Energy Authority. At the time the Atlas was the world’s most powerful computing device and according to computer historians when it was switched on the UK's scientific computing capacity instantly doubled.

In the period after World War II, Manchester was one of foremost centers of computing expertise. Tom Kilburn's group had completed the  Small-Scale Experimental Machine (SSEM) better known as "Baby“ in 1948 and followed on with the wold's first stored program computer, Manchester Mark I in 1949. Its next machine, the Mark II or MEG, standing for MEGacycle, was converted into a commercial machine by Ferranti with the support of the NRDC (National Research and Development Council) which in 1951 agreed to order four machines.

Despite this early lead, by the mid 1950's there was a dearth of computing power available. Professor Simon Lavington, who started using Atlas as a research student in 1962, and who has produced an illustrated pdf, The Atlas Story, tells us that by 1955 there were fewer than 16 production digital computers in use in the UK and they were all single-user systems with practically no systems software; each had primary memories of 4K bytes or less and could obey about 1,000 instructions per second.

Tom Kilburn's impetus to build a more ambitious machine stemmed, according to Lavington, to two factors:

the urgent need of the UK’s nuclear physicists for more powerful computers, and the knowledge that the Americans were planning new machines such as the IBM STRETCH that could probably satisfy the physicists’ needs. In short, the early lead in computers that the UK had achieved in the period 1948 – 51 had slipped away.