Automatic Computing Engine

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The Automatic Computing Engine (ACE) was an early electronic computer, designed in Britain; it was designed by Alan Turing in 1946.

On February 19, 1946 Turing presented a paper to the National Physical Laboratory (NPL) Executive Committee, giving the first complete design of a stored-program computer. Unlike most other early computers, it owed nothing to the EDVAC that was built by John von Neumann for the U.S. Army Ordinance Department; it was a completely independent design which was contemporaneous with EDVAC. Turing had already published a design for a universal machine, later to be known as the Universal Turing machine, in 1936.

In 1945 the University of Pennsylvania's Moore School of Engineering put into operation a computer called the ENIAC designed by John Mauchley and J. Prosper Eckert. The programming of the ENIAC however was built into its hardware. The EDVAC had a stored program opposed to the ENIAC's cable-based programming system. John von Neumann however claimed never to have read Alan Turing's paper on the design of a universal machine that used a tape input.

The ACE had a 48-bit word. It used delay line main memory, and contained about 7000 vacuum tubes compared to the ENIAC's 17,468 vacuum tubes, 70,000 resistors, 10,000 capacitors, and 5 million soldered joints. Its multiplication time was about 448 microseconds.

Turing's report on the ACE was published in 1945 including detailed logical circuit diagrams and a cost estimate of ₤11,200. The ACE also implemented subroutine calls, whereas the EDVAC did not, and what also set the ACE apart from the EDVAC was the use of Abbreviated Computer Instructions, an early form of programming language. Due to various difficulties, the first version of the ACE actually built was the Pilot ACE, a smaller version of Turing's original complete design. The full-scale version (DEUCE) was constructed later, in the late 1950s; it was working by late 1957, but was already obsolete, due to its reliance on delay-line main memory.

[edit] References

B. J. Copeland (Ed.), 2005. Alan Turing's Automatic Computing Engine. OUP, Oxford. ISBN 0-19-856593-3.
B. E. Carpenter, R. W. Doran, 1986. A. M. Turing's ACE Report of 1946 and Other Papers. MIT Press, Cambridge.
David M. Yates, 1997. Turing's Legacy: A History of Computing at the National Physical Laboratory, 1945-1995. Science Museum, London.
Simon H. Lavington, 1980. Early British Computers: The Story of Vintage Computers and The People Who Built Them. Manchester University Press.
J. H. Wilkinson, 1980. Turing's Work at the National Physical Laboratory and the Construction of Pilot ACE, DEUCE and ACE. In N. Metropolis, J. Howlett, G.-C. Rota, (Eds.), A History of Computing in the Twentieth Century, Academic Press, New York, 1980.