Electronic Delay Storage Automatic Calculator

Electronic delay storage automatic calculator (EDSAC) was an early British computer. Inspired by John von Neumann's seminal First Draft of a Report on the EDVAC, the machine was constructed by Maurice Wilkes and his team at the University of Cambridge Mathematical Laboratory in England. EDSAC was the second electronic digital stored-program computer to go into regular service.

Later the project was supported by J. Lyons & Co. Ltd., a British firm, who were rewarded with the first commercially applied computer, LEO I, based on the EDSAC design. Work on EDSAC started during 1947, and it ran its first programs on 6 May 1949, when it calculated a table of squares and a list of prime numbers. EDSAC 1 was finally shut down on 11 July 1958, having been superseded by EDSAC 2, which remained in use until 1965.

As soon as EDSAC was operational, it began serving the University's research needs. It used mercury delay lines for memory, and derated vacuum tubes for logic. Cycle time was 1.5 ms for all ordinary instructions, 6 ms for multiplication. Input was via five-hole punched tape and output was via a teleprinter.

Initially registers were limited to an accumulator and a multiplier register. In 1953, David Wheeler, returning from a stay at the University of Illinois, designed an index register as an extension to the original EDSAC hardware.

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