Percy Ludgate
More info
- Born
- 2 August 1883, Skibbereen
- Died
- 16 October 1922, Dublin
- Known for
- The 1909 analytical machine, Irish logarithms
- Nationality
- Irish
A Dublin accountant designed the world's second computer on paper in 1909, independently of Babbage, and died before anyone thought to ask for the drawings.
Ludgate studied accountancy in the evenings and drew at night. His paper On a Proposed Analytical Machine, published by the Royal Dublin Society in April 1909, describes a program-controlled general-purpose machine: 192 variables of twenty decimal digits each, stored on shuttles in a rotating shuttle box, program on perforated tape, conditional control. He only learned of Babbage's work after he had started on his own.
The multiplication scheme is his real contribution. Instead of repeated addition he used what he himself called Irish logarithms: a hand-built table assigning each digit a small integer index, chosen so that a product becomes an addition of indices plus a reverse lookup. The trick made multiplication cheap enough that the whole machine would fit in a case under seventy centimetres long — a portable computer, unlike Babbage's room-filling gearwork.
Nothing was built. Ludgate spent the war working on logistics for the Irish oat harvest, died of pneumonia in 1922 at thirty-nine, and his drawings have never been found. What survives is the 1909 paper and a short 1914 article — the sum of what we know about the second computer anyone ever designed.