Percy Ludgate

Percy Edwin Ludgate (2 August 1883 – 16 October 1922) was an Irish amateur scientist who, in 1909, designed an analytical engine (a general-purpose Turing-complete computer, and the second of its kind). This machine was to be capable of storing 192 numbers, each containing 20 digits, and as part of the design, he devised a number of novel techniques, including Irish logarithms.

Life Ludgate was born on 2 August 1883 in Skibbereen, County Cork, to Michael Ludgate and Mary McMahon. In the 1911 census, he is also in Dublin, as a Commercial Clerk (Corn Merchant). He studied accountancy at Rathmines College of Commerce, earning a gold medal based on the results of his final examinations in 1917. At some date before or after then, he joined Kevans & Son, accountants. as well as a novel memory system utilizing concentric cylinders, storing numbers as displacements of rods in shuttles. His design featured several other novel features, including for program control (e.g., preemption and subroutines – or microcode, depending on one's viewpoint). The design is so dissimilar from Babbage's that it can be considered a second, unique type of analytical engine, which thus preceded the third (electromechanical) and fourth (electronic) types. The engine's precise mechanism is unknown, as the only written accounts which survive do not detail its workings, although he stated in 1914 that "omplete descriptive drawings of the machine exist, as well as a description in manuscript" – these have never been found.

Ludgate was one of just a few independent workers in the field of science and mathematics. His inventions were worked on outside a lab. He worked on them only part-time, often until the early hours of the morning. Many publications refer to him as an accountant, but that came only after his 1909 analytical engine paper. Little is known about his personal life, as his only known records are his scientific writings. Prior to 2016, the best source of information about Ludgate and his significance was in the work of Professor Brian Randell. Since then, further investigation is underway at Trinity College, Dublin under the auspices of the John Gabriel Byrne Computer Science Collection.

Ludgate died of pneumonia on 19 October 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 honour, and in 2016 the Ludgate Hub e-business incubation centre was opened in Skibbereen, where he was born.

Also in 2022, a podcast with Dr Chris Horn discussed Percy Ludgate, then in October 2024 a podcast on Percy Ludgate was created by Google's Gemini A.I..