Ludgate, Percy Edwin (1883–1922), pioneer in digital computing, was born 2 August 1883 at the house of his parents, Michael Ludgate and Mary (née McMahon), in Townsend Street, Skibbereen, Co. Cork, the youngest of at least eight children. His father taught shorthand, later joined by some of Ludgate’s elder siblings, and from 1890 the family lived in Foster Terrace, Ballybough, Dublin.
Ludgate attended St George’s school in Dublin’s north inner city from 1890–92; where he undertook the remainder of his schooling, then required until aged fourteen, is not known. In 1898 Ludgate became a ‘boy copyist’ in the Irish civil service. He and his elder brother Alfred were living with their mother, Mary, at 30 Dargle Road, Drumcondra, in 1901; Michael Ludgate was living in Balbriggan, suggestive of marital breakdown.
Percy was working in the National Education Office when, in March 1903, he came first in Ireland in the civil service exams for ‘abstractors’ (assistant clerks). Although he passed the medical examination he was not recruited, while the next six ranked candidates were; the reason for this remains unknown. His ‘boy copyist’ post expired when he reached the age of twenty in August 1903. In October 1904 he passed the civil service exams for second-division clerkships, but on this occasion failed the medical exam. T. C. Harrington (qv), MP for Dublin Harbour, raised the issue in the house of commons in February 1905, petitioning for a new medical examination for Ludgate, but to no avail. By 1911 Percy was working as a commercial clerk to a corn merchant and later that decade began working with the accounting firm of Kevans & Son, 31 Dame Street, Dublin. He studied accountancy at the Rathmines College of Commerce and qualified in 1917, being awarded a gold medal. He remained with Kevans & Son until his death.
Ludgate is best known for his work in the field of computational mathematics and is the earliest known successor to Charles Babbage, the Victorian scientist and mathematician who invented, in 1834, most of the fundamental concepts involved in the modern digital computer, well over a century before the first such computers saw the light of day. In 1903 Ludgate had commenced work on a computational device, as described in his paper ‘On a proposed analytical machine’, published in the Scientific Proceedings of the Royal Dublin Society in April 1909. Sir Charles Vernon Boys, fellow of the Royal Society (FRS), and eminent British physicist and an expert in calculating machines, reviewed Ludgate’s paper in the 1 July 1909 issue of the prestigious journal Nature.
Though Ludgate asserted that he was unaware of Babbage’s ‘analytical engine’ when completing the first iteration of his own ‘machine’, he stated that ‘I have since been greatly assisted in the more advanced stages of the problem by … the writings of that accomplished scholar’ (Ludgate, 78). Ludgate’s machine incorporated fully automatic mechanisms for storing and accessing nearly 200 twenty-digit decimal numbers, and executing a sequence of the arithmetical operations (addition, subtraction, multiplication and division) on these numbers under the control of a punched paper tape. His design comprised four main parts: the arithmetic unit, storage, input and output, and a sequencing mechanism. The arithmetic unit performed calculations using a device called a ‘mill’, as had Babbage’s. However, Ludgate introduced an ‘index’ to undertake multiplication, employing novel discrete logarithms which Boys described in Nature as ‘Irish logarithms’ (Boys, 14).
Apart from the mill, these mechanisms were both novel and ingenious – and significantly different from any devised previously. For example, Ludgate’s index could undertake multiply–accumulation calculations (MAC), comprising multiplication followed by addition to any previous result in the mill. This makes Ludgate’s analytical machine the first computer arithmetic unit to undertake such calculations, later widely utilised in digital signal processing (deployed in radar, radio astronomy and elsewhere), and also in deep artificial intelligence research. For storage, he used the lateral position of a sliding rod to represent a decimal digit, holding numbers in shuttles within rotatable cylinders, an entirely novel approach. Indeed, his techniques of what would later be termed ‘programme control’ and ‘storage addressing’ were significant advances on Babbage’s work. Ludgate understood the fundamental importance of being able to change the sequence of calculations based on previous results (later known as ‘conditional branching’).
There is no evidence that Ludgate ever made any attempt to build his machine, essentially the world’s second ever design for a computer, and beyond his paper and Boys’s report his work largely passed without mention. He contributed a second paper, ‘Automatic calculating machines’, to the Handbook of the Napier tercentenary celebration (1914). This focused on Babbage’s ‘analytical engine’ and modestly only briefly mentioned his own 1909 design for such a machine.
Percy Ludgate died on 16 October 1922 at 30 Dargle Road, where he had been nursed while sick by his late brother Frederick’s wife, Alice, who then died six days later. His death certificate lists the cause of death as catarrhal pneumonia, which mostly accompanies diseases like influenza. He was buried in the family grave at Mount Jerome cemetery, Harold's Cross, Dublin, which for a long time was unmarked before a grave marker was erected in 2019. Little is known of Ludgate’s personal life. However, a colleague in accountancy later recounted that Ludgate ‘possessed characteristics one usually associates with genius’, while his niece recalled that he ‘took long solitary walks ...[and] always appeared to be thinking deeply’ (Randell, 319). New research into Ludgate’s life and career since 2016 has drawn together a variety of sources and interested experts, generating new genealogical and biographical data. A summation of this research asserts Ludgate ‘designed a potentially disruptive mechanical technology; his storage scheme was extremely compact; his index would have dramatically reduced average multiplication times relative to repeated addition; these and his approach to division were novel’ (Coghlan et al., 26). Archival material unearthed during this renewed interest in Ludgate’s life is housed in the John Gabriel Byrne Computer Science Collection at Trinity College Dublin, while a collection of essays published in 2022 addresses various facets of his life and career. A plaque in honour of Percy Ludgate was unveiled at 30 Dargle Road in October 2022, to mark the centenary of his death.