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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 ...
A single program deck, with individual subroutines marked. The markings show the effects of editing, as cards are replaced or reordered. Many early programming languages, including FORTRAN, COBOL and the various IBM assembler languages, used only the first 72 columns of a card – a tradition that traces back to the IBM 711 card reader used on the IBM 704/709/7090/7094 series (especially the ...
A U.S. Census Bureau clerk (left) prepares punch cards using a pantograph similar to that developed by Herman Hollerith for the 1890 Census, while a second clerk (right) uses a 1930s key punch to perform the same task more quickly. A wall-sized display sample of a punch card for the 1954 U.S. Census of Agriculture
Early computers were capable of running only one program at a time. Each user had sole control of the machine for a scheduled period of time. They would arrive at the computer with program and data, often on punched paper cards and magnetic or paper tape, and would load their program, run and debug it, and carry off their output when done.
For example, one hole might record the answer to a yes/no question on a survey, with the presence of a notch meaning "yes". More-complex data was encoded using a variety of schemes, often using a superimposed code which allows more distinct categories to be coded than the number of holes available.
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.
This category contains articles about punched cards and card handling equipment, including card readers, card punches, and keypunches. Subcategories This category has the following 2 subcategories, out of 2 total.
The cycles were divided into points according to when the rows on a punched card would appear under a read or punch station. On most [6] machines, cards were fed face down, 9-edge (bottom edge) first. Thus the first point in a card cycle would 9-time, the second 8 time and so on to 0-time. The times from 9 to 0 were known as digits.