The Manchester computers were an innovative series of stored-program electronic computers developed during the 30-year period between 1947 and 1977 by a small team at the University of Manchester, under the leadership of Tom Kilburn. They included the world's first stored-program computer, the world's first transistorised computer, and what was the world's fastest computer at the time of its inauguration in 1962.
The project began with two aims: to prove the practicality of the Williams tube, an early form of computer memory based on standard cathode-ray tubes (CRTs); and to construct a machine that could be used to investigate how computers might be able to assist in the solution of mathematical problems. The first of the series, the Manchester Baby, ran its first program on 21 June 1948. As the world's first stored-program computer, the Baby, and the Manchester Mark 1 developed from it, quickly attracted the attention of the United Kingdom government, who contracted the electrical engineering firm of Ferranti to produce a commercial version. The resulting machine, the Ferranti Mark 1, was the world's first commercially available general-purpose computer.
The collaboration with Ferranti eventually led to an industrial partnership with the computer company ICL, who made use of many of the ideas developed at the university, particularly in the design of their 2900 series of computers during the 1970s.
Manchester Baby
The Manchester Baby was designed as a test-bed for the Williams tube, an early form of computer memory, rather than as a practical computer. Work on the machine began in 1947, and on 21 June 1948 the computer successfully ran its first program, consisting of 17 instructions written to find the highest proper factor of 218 (262,144) by trying every integer from 218 − 1 downwards. The program ran for 52 minutes before producing the correct answer of 131,072.
The Baby was in length, tall, and weighed almost 1 long ton. It contained 550 thermionic valves – 300 diodes and 250 pentodes – and had a power consumption of 3.5 kilowatts. Its successful operation was reported in a letter to the journal Nature published in September 1948, establishing it as the world's first stored-program computer. It quickly evolved into a more practical machine, the Manchester Mark 1.
Manchester Mark 1
Development of the Manchester Mark 1 began in August 1948, with the initial aim of providing the university with a more realistic computing facility. In October 1948 UK Government Chief Scientist Ben Lockspeiser was given a demonstration of the prototype, and was so impressed that he immediately initiated a government contract with the local firm of Ferranti to make a commercial version of the machine, the Ferranti Mark 1.
Two versions of the Manchester Mark 1 were produced, the first of which, the Intermediary Version, was operational by April 1949. The Final Specification machine, which was fully working by October 1949, contained 4,050 valves and had a power consumption of 25 kilowatts. Perhaps the Manchester Mark 1's most significant innovation was its incorporation of index registers, commonplace on modern computers.
In June 2022 an IEEE Milestone was dedicated to the "Manchester University "Baby" Computer and its Derivatives, 1948-1951".
Meg and Mercury
As a result of experience gained from the Mark 1, the developers concluded that computers would be used more in scientific roles than pure maths. They therefore embarked on the design of a new machine which would include a floating-point unit; work began in 1951. The resulting machine, which ran its first program in May 1954, was known as Meg, or the megacycle machine. It was smaller and simpler than the Mark 1, as well as quicker at solving maths problems. Ferranti produced a commercial version marketed as the Ferranti Mercury, in which the Williams tubes were replaced by the more reliable core memory.
Transistor Computer
Work on building a smaller and cheaper computer began in 1952, in parallel with Meg's ongoing development. Two of Kilburn's team, Richard Grimsdale and D. C. Webb, were assigned to the task of designing and building a machine using the newly developed transistors instead of valves, which became known as the Manchester TC. Initially the only devices available were germanium point-contact transistors, less reliable than the valves they replaced but which consumed far less power.