Encyclopedia of Computer Science and Technology

BBabbage, Charles(1791–1871)BritishMathematician, InventorCharles Babbage made wide-ranging applications of mathematicsto a variety of fields including economics, socialstatistics, and the operation of railroads and lighthouses.Babbage is best known, however, for having conceptualizedthe key elements of the general-purpose computer about acentury before the dawn of electronic digital computing.As a student at Trinity College, Cambridge, Babbagewas already making contributions to the reform of calculus,championing new European methods over the Newtonianapproach still clung to by British mathematicians.But Babbage’s interests were shifting from the theoreticalto the practical. Britain’s growing industrialization as wellas its worldwide interests increasingly demanded accuratenumeric tables for navigation, actuarial statistics, interestrates, and engineering parameters. All tables had to behand-calculated, a long process that inevitably introducednumerous errors. Babbage began to consider the possibilitythat the same mechanization that was revolutionizingindustries such as weaving could be turned to the automaticcalculation of numeric tables.Starting in 1820, Babbage began to build a mechanicalcalculator called the difference engine. This machineused series of gears to accumulate additions and subtractions(using the “method of differences”) to generatetables. His small demonstration model worked well,so Babbage undertook the full-scale “Difference EngineNumber One,” a machine that would have about 25,000moving parts and would be able to calculate up to 20 decimalplaces. Unfortunately, Babbage was unable, despitefinancial support from the British government, to overcomethe difficulties inherent in creating a mechanicaldevice of such complexity with the available machiningtechnology.Undaunted, Babbage turned in the 1830s to a new designthat he called the Analytical Engine. Unlike the DifferenceEngine, the new machine was to be programmable usinginstructions read in from a series of punch cards (as in theJacquard loom). A second set of cards would contain thevariables, which would be loaded into the “store”—a seriesof wheels corresponding to memory in a modern computer.Under control of the instruction cards, numbers could bemoved between the store and the “mill” (corresponding to amodern CPU) and the results of calculations could be sentto a printing device.Collaborating with Ada Lovelace (who translated his lecturetranscripts by L. F. Menebrea) Babbage wrote a seriesof papers and notes that explained the workings of the proposedmachine, including a series of “diagrams” (programs)for performing various sorts of calculations.Building the Analytical Engine would have been a farmore ambitious task than the special-purpose DifferenceEngine, and Babbage made little progress in the actual constructionof the device. Although Babbage’s ideas wouldremain obscure for nearly a century, he would then be recognizedas having designed most of the key elements of themodern computer: the central processor, memory, instructions,and data organization. Only in the lack of a capability35