An Irish accountant designed an early mechanical 'computer' that included many of the features of a modern electronic system, writes Mary Mulvihill
Since the invention of the abacus people have been trying to build ever more complex calculating machines, and in 1909 an Irish accountant, Percy Ludgate, designed a new and powerful "analytical machine".
Programmable, portable, efficient and simple, yet capable of doing complex calculations, it is given a prominent place in the history of computing. Sadly, it was never made and Ludgate's drawings have been lost, so we may never see a working model of this pioneering Irish calculating engine.
Percy Ludgate was born in Skibbereen in 1883 and studied at Rathmines College of Commerce, before joining a Dublin firm of accountants. His spare time was spent designing his analytical machine and in 1909 he presented the details to the Royal Dublin Society which brought him to international attention, and in 1914 he lectured in Edinburgh at a special conference on mathematics and computing.
Englishman Charles Babbage (1791-1871), spent years and a vast fortune attempting to build programmable calculating machines. His ideas were based on the Jacquard weaving loom, where punched cards controlled the patterns. Babbage's machines were intricate and cumbersome and only small sections were built. Even these were enormous, ponderously slow - everything was reduced to addition or subtraction - and required thousands of precision-engineered metal parts, They would never be mass produced,and it was not until 1991 that the first complete Babbage engine was made.
Percy Ludgate's design was also based on the Jacquard loom, but in all other respects differed from Babbage's. Where Babbage used columns of toothed discs to store numbers Ludgate opted for a simpler shuttle mechanism. Significantly, Ludgate's design had all the elements of a modern computer: a mechanism for storing data, ways to input data and to program the machine, a printer, and even an "operating system". Ludgate introduced two further features not seen before: his machine could be stopped at any stage mid-calculation to add new variables, and it could do subroutines.
Ludgate's approach to calculations was also unusual. For multiplication he developed a technique using partial products. For division he used a table of reciprocals and a rapidly converging series using subroutines. In theory, Ludgate's engine would multiply two 20-digit numbers in under 10 seconds, and take two minutes to determine the logarithm of a number. It would also solve algebraic equations and geometric problems.
Ludgate envisaged it would be powered by an electrical motor, and the calculations automated, and the complete device - a cube measuring about 60cm on a side - would be portable.
But the machine was probably never made. World War I intervened, Ludgate moved onto other things, and in 1922 he died of pneumonia.
Ludgate is one of the inventors featured in Mary Mulvihill's new book, Ingenious Ireland, a county by county exploration of Irish mysteries and marvels (Town House, €30)