s to feed in automatically a specified number of cards from a "read-in" station; perform such operations as addition, multiplication, and sorting; and feed out cards punched with results. The machines were slow, typically processing from 50 to 250 cards per minute, with each card holding up to 80 decimal numbers. At the time, however, punched cards were an enormous step forward. Automatic Digital ComputersBy the late 1930s punched-card machine techniques had become well established and reliable, and several research groups strove to build automatic digital computers. An IBM team led by Howard Hathaway Aiken built one promising machine, constructed of standard electromechanical parts. Aiken's machine, called the Harvard Mark I, handled 23-decimal-place numbers (words) and could perform all four arithmetic operations. Moreover, it had special built-in programs, or subroutines, to handle logarithms and trigonometric functions. The Mark I was originally controlled from prepunched paper tape without provision for reversal, so that automatic "transfer of control" instructions could not be programmed. Output was by cardpunch and electric typewriter. Although the Mark I used IBM rotating counter wheels as key components in addition to electromagnetic relays, the machine was classified as a relay computer. It was slow, requiring 3 to 5 seconds for a multiplication, but it was fully automatic and could complete long computations. Mark I was the first of a series of computers designed and built under Aiken's direction. Electronic Digital ComputersThe outbreak of World War II produced a desperate need for computing capability, especially for the military. New weapons systems were produced for which trajectory tables and other essential data were lacking. In 1942, J. Presper Eckert, John W. Mauchly, and their associates at the Moore School of Electrical Engineering of the University of Pennsylvania decided to build a high-speed electronic comput...
