Replica of the 'Baby' or SSEM computer

Working replica of the Manchester “Baby” computer, also known as the SSEM (Small Scale Experimental Machine). The original Baby, built in 1948 at the University of Manchester, was the world's first stored-program computer; the first machine to function like most of our computers today.

The developers of Baby, Frederic Williams, Tom Kilburn and Geoff Tootill, had been wartime radar designers. After the Second World War ended, they began developing a way of storing data electronically using a cathode-ray tube (CRT). They built Baby to prove that their CRT computer memory worked.

A CRT was more typically used as a television, but their idea was to use the CRT screen to store a pattern of dots representing the ones and zeros of binary code, which could be used to hold a simple program that could run on the computer. With the CRT memory, Baby could be relatively easily reprogrammed to do all sorts of tasks, just like our computers today.

Baby’s electronics circuits were made of thermionic valves, over 500 of them, mostly government surplus spare parts originally intended for wartime radar sets. The bulk of these components gave the machine its large size compared to later electronics. Despite weighing around a ton, Baby was a very simple experimental computer. It could do about 700 operations a second and the main memory held 1024 binary ones or zeros, a tiny fraction of the power of our computers today. Although of limited power, it proved the whole concept of the stored program computer, an idea still at the heart of how computers work today.

After around two years of development, Baby ran its first program on 21 June 1948. The first and second programs, written by Tom Kilburn and Geoff Tootill respectively, were mathematical problems intended to test the machine. A third program, for long division, was written by the famous mathematician Alan Turing, who moved to Manchester later that year. The original Baby only lasted a few months. It was quickly upgraded into a more powerful computer, the Manchester Mark 1. Ferranti, a major Manchester engineering firm, adopted this design as the basis for the world’s first commercially manufactured computer, the Ferranti Mark 1.

This working replica was built by the Computer Conservation Society in 1998 to celebrate Baby’s 50th anniversary. It is built of vintage electronics from the period and designed to mirror the state of the original as it was on 21 June 1948.