Electromechanical machines which processed data using punch cards
Starting at the end of the nineteenth century, well before the advent of electronic computers, data processing was performed using electromechanical machines collectively referred to as unit record equipment, electric accounting machines (EAM) or tabulating machines.[1][2][3][4]
Unit record machines came to be as ubiquitous in industry and government in the first two-thirds of the twentieth century as computers became in the last third. They allowed large volume, sophisticated data-processing tasks to be accomplished before electronic computers were invented and while they were still in their infancy. This data processing was accomplished by processing punched cards through various unit record machines in a carefully choreographed progression.[5] This progression, or flow, from machine to machine was often planned and documented with detailed flowcharts that used standardized symbols for documents and the various machine functions.[6] All but the earliest machines had high-speed mechanical feeders to process cards at rates from around 100 to 2,000 per minute, sensing punched holes with mechanical, electrical, or, later, optical sensors. The operation of many machines was directed by the use of a removable plugboard, control panel, or connection box.[7] Initially all machines were manual or electromechanical. The first use of an electronic component was in 1937 when a photocell was used in a Social Security bill-feed machine.[8]: 65 Electronic components were used on other machines beginning in the late 1940s.
The term unit record equipment also refers to peripheral equipment attached to computers that reads or writes unit records, e.g., card readers, card punches, printers, MICR readers.
IBM was the largest supplier of unit record equipment and this article largely reflects IBM practice and terminology.
Sheet 1 of Hollerith's U.S. Patent 395,782 showing his early concept for recording statistical information by means of holes punched in paper.
^Origin of the term unit record: It was in 1888 that Mr. Davidson conceived the idea... The idea was that the card catalog, then in fairly general use by libraries, could be adapted with advantage to certain 'commercial indexes'. ... Directly connected with these is one of the most important principles of all - the 'unit record' principal in business. Hitherto, the records of a business house had been kept, each for one fixed purpose, and their usefulness had been restricted by the inflexible limitations of a bound book. The unit record principle, made possible by the card system, gave to these records a new accessibility and significance. ...The Story of the Library Bureau. Cowen Company, Boston. 1909. p. 50.
^By 1887 ...Doctor Herman Hollerith had worked out the basis for a mechanical system of recording, compiling and tabulating census facts... Each card was used to record the facts about an individual or a family - a unit situation. These cards were the forerunners of today's punched cards or unit records. General Information Manual: An Introduction to IBM Punched Card Data Processing. IBM. p. 1.
^Data processing equipment can be divided into two basic types - computers and unit record machines. Unit Record derives form the common use of punchcards to carry information on a one-item-per-card basis, which makes them unit records. Janda, Kenneth (1965). Data Processing. Northwestern University Press. p. 47.
^Like the index card, the punched card is a unit record containing one kind of data, which can be combined with other kinds of data punched in other cards. McGill, Donald A.C. (1962). Punched Cards, Data Processing for Profit Improvement. McGraw-Hill. p. 29.
^International Business Machines Corp. (1957). Machine Functions(PDF). 224-8208-3. {{cite book}}: |author= has generic name (help)
^International Business Machines Corp. (1959). Flow Charting and Block Diagramming Techniques(PDF). /C20-8008-0. {{cite book}}: |author= has generic name (help)
^Cemach, Harry P., 1951, The Elements of Punched Card Accounting, Pitman, p.27. Within certain limits the information punched in any column of a card can be reproduced in any desired position by the tabulator. This is achieved by means of a Connection Box. ... The connection box can be easily removed from the tabulator and replaced by another.
^Pugh, Emerson W. (March 16, 1995). Building IBM: Shaping an Industry and Its Technology. MIT Press. ISBN 978-0262161473.
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