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A punched card (also punch card [1] or punched-card [2]) is a piece of card stock that stores digital data using punched holes. Punched cards were once common in data processing and the control of automated machines .
A computer punched card reader or just computer card reader is a computer input device used to read computer programs in either source or executable form and data from punched cards. A computer card punch is a computer output device that punches holes in cards. Sometimes computer punch card readers were combined with computer card punches and ...
Depending on the programming language, debugging output statements could be quickly activated and "commented out" by using cards with such statements punched with the comment character (e.g., 'C' in Fortran) in column 80 of the card; turning the card end-for-end would put the 'C' in the leading column, which transformed the now backwards card's ...
The first combination of card punch and typewriter, permitting selected text to be typed and punched, was developed by the Powers company in 1925. [23] The IBM 824 Typewriter Card Punch was an IBM 024 where the 024 keyboard was replaced by an IBM electric typewriter. [24] Similarly, the IBM 826 used an IBM 026 Keypunch. [25]
Punch cards were created in 1890 and were used as input devices for computers. The use of punch cards declined greatly in the early 1970s with the introduction of personal computers. [8] With modern OMR, where the presence of a pencil filled in bubble is recognized, the recognition is done via an optical scanner.
Cards were sorted on one card column at a time; sorting on, for example, a five digit zip code required that the card deck be processed five times. Sorting an input card deck into ascending sequence on a multiple column field, such as an employee number, was done by a radix sort , bucket sort , or a combination of the two methods.
Aperture cards are used for engineering drawings from all engineering disciplines. The U.S. Department of Defense once made extensive use of aperture cards, and some are still in use, but most data is now digital. [2] Information about the drawing, for example the drawing number, could be both punched and printed on the remainder of the card.
A notched card showing two levels of notching. Edge-notched cards or edge-punched cards are a system used to store a small amount of binary or logical data on paper index cards, encoded via the presence or absence of notches in the edges of the cards. [1]