Percy Ludgate

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Percy Edwin Ludgate (2 August 1883 – 16 October 1922) was an accountant in Dublin and designer of an analytical engine.

Working alone, Ludgate designed an analytical engine while unaware of Charles Babbage's designs, although he later went on to write about Babbage's machine. Ludgate's engine used multiplication as its base mechanism unlike Babbage's which used addition, Ludgate's engine used rods similar to slide rules. Its precise mechanism is unknown as the only written accounts of the engine which survive do not detail its workings.

Ludgate also helped advance calculators by expanding Charles Babbage's design for the first programmable computer. He was one of a few independent workers in the field of science and mathematics. His inventions were worked on outside a lab. He worked on the inventions only part-time.

His design featured several novelties, including a method of implementing multiplication referred to at the time as "Irish logarithms". (Boys, 1904)

Little is known about Ludgate's life, as his only records are his scientific writings. The best source of information about Ludgate and his significance lie in the work of Professor Brian Randell. A further investigation is underway at Trinity College, Dublin under the auspices of the John Gabriel Byrne Computer Science Collection.

He died of pneumonia in 1922.

In 1991, a prize for the best final year project in the Moderatorship in computer science course at Trinity College, Dublin – the Ludgate Prize – was instituted in his honor.


  • C. V. Boys (July 1909). "A new analytical engine". Nature. 81 (2070): 14–15. doi:10.1038/081014a0.
  • Ludgate, Percy E. (April 1909). "On a proposed analytical machine". Scientific Proceedings of the Royal Dublin Society. 12 (9): 77–91. Available on-line at:
  • Ludgate, P. E. (1914). "Automatic calculating machines". In Ellice Martin Horsburgh. Napier tercentenary celebration: Handbook of the exhibition of Napier relics and of books, instruments, and devices for facilitating calculation. Royal Society of Edinburgh. pp. 124–127.
  • Brian Randell (1971). "Ludgate's analytical machine of 1909". The Computer Journal. 14 (3): 317–326. doi:10.1093/comjnl/14.3.317. (A subscription to the journal or payment on a per-article basis is required to view this article)
  • Brian Randell (1982). "From analytical engine to electronic digital computer: The contributions of Ludgate, Torres, and Bush" (PDF). IEEE Annals of the History of Computing. 4 (4): 327–341. doi:10.1109/MAHC.1982.10042.
  • "The Feasibility of Ludgate's Analytical Machine".
  • "Percy E. Ludgate" (PDF). In: online catalog of The John Gabriel Byrne Computer Science Collection