Before the advent of electronic computers, data processing was performed using electromechanical devices called unit record equipment, electric accounting machines (EAM) or tabulating machines. Unit record machines were as ubiquitous in industry and government in the first half of the twentieth century as computers became in the second half. They allowed large volume, sophisticated, data-processing tasks to be accomplished long before modern (electronic) computers were invented. This data processing was accomplished by processing decks of punched cards through various unit record machines in a carefully choreographed progression. This progression, or flow, from machine to machine was often planned and documented with drawings that used standardized symbols for the various machine functions, drawings that today would be called flowcharts. The machines all had high-speed mechanical feeders to process from around one hundred cards per minute, to 2,000 cards per minute, sensing punched holes with either electrical or optical sensors. The operation of many machines was directed by the use of a removable control panel. Initially all machines were constructed using electromechanical counters and relays. Electronic components were introduced on some machines beginning in the late 1940s.
The largest supplier of unit record equipment was IBM and this article largely reflects IBM practice and terminology.
Read more about Unit Record Equipment: Punched Cards, Keypunching, Sorting, Tabulating, Paper Handling Equipment, Card Punching, Collating, Interpreting, Transmission of Punched Card Data, Processing Punched Tape, Control Panel Wiring
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