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Cambridge University's Edsac, or Electronic Delay Storage Automatic Calculator, pictured above, is considered the first practical example of a machine holding program instructions in memory.
However, the significance of Edsac and the Manchester Mark 1 does not stop there. Both machines went on to form the basis of two milestone commercial systems: Edsac spawned Leo 1, while the Manchester computer was the immediate forerunner of the Ferranti Mark 1.
Leo 1 was the world's first business computer. From September 1951, it ran an application called Bakeries Valuations, organising logistics for catering company Lyons's famous tea shops and London Corner Houses.
The Ferranti Mark 1 became the world's first commercially available computer in February 1951, beating America's Univac 1 to market by as little as one month, according to some estimates.
Photograph © 2008 University of Cambridge Computer Laboratory. Reproduced by permission