Babbage Charles (1792–1871), English applied mathematician, inventor, and expert on machinery and manufacturing. His chief interest was in developing mechanical ‘engines’ to compute tables of functions. Until the invention of the electronic computer, printed tables of functions were important aids to calculation.
Babbage invented the difference engine, a machine that consisted of a series of accumulators each of which, in turn, transmitted its contents to its successor, which added to them to its own contents. He built only a model, but George and Edvard Scheutz built difference engines that were actually used. Though tables of squares and cubes could be calculated by a difference engine, the more commonly used tables of logarithms and of trigonometric functions could not. To calculate these and other useful functions, Babbage conceived of the analytical engine, a machine for numerical analysis.
The analytical engine was to have a store (memory) and a mill (arithmetic unit). The store was to hold decimal numbers on toothed wheels, and to transmit them to the mill and back by means of wheels and toothed bars. The mill was to carry out the arithmetic operations of addition, subtraction, multiplication, and division mechanically, greatly extending the technology of small calculators. The operations of the mill were to be governed by pegged drums, derived from the music box.
A desired sequence of operations would be punched on cards, which would be strung together like the cards of a Jacquard loom and read by the machine. The control mechanisms could branch and execute a different sequence of cards when a designated quantity changed sign. Numbers would be entered from punched cards and the answers punched on cards. The answers might also be imprinted on metal sheets from which the calculated tables would be printed, thus avoiding the errors of proofreading.
Although Babbage formulated various partial plans for the analytical engine and built a few pieces of it, the machine was never realized. Given the limitations of mechanical computing technology, building an analytical engine would probably not have been an economical way to produce numerical tables. The modern electronic computer was invented and developed completely independently of Babbage’s pioneering work. Yet because of it, Babbage’s work has been publicized and he has become famous. See also COMPUTER THEORY. A.W.B.