(or punched card), a recording medium in the form of a card made of paper, paperboard, or, more rarely, plastic and of a standard shape and size; data are recorded on the card by the punching of holes. Punch cards are used primarily for the input and output of data in computers and as the basic recording medium in punch-card processing equipment. They exist in many types, which differ in shape, size, volume of information stored, and the shape and arrangement of the holes. Most of the punch cards used in the USSR have 80 columns—45-column cards are encountered in obsolete computer units—and are made of heavy paper stock 0.18 mm thick in the shape of a rectangle with sides of 187.4 and 82.5 mm. The top left corner of the card is cut off for convenience in sorting and stacking. The columns are marked off across the card from left to right. The card is also divided into 12 rows—10 primary and 2 supplementary. Up to 80 characters—approximately 10 to 15 words—can be recorded on one punch card. The processing rate for machine punch cards can reach 2,000 cards/min. Data are read by means of electromechanical readers or photoelectric cells. Punch cards with 90, 40, and 21 columns and 6, 12, and 10 rows, respectively, are also used in other countries. Special forms of punch cards are edge-punched cards, which are used in information systems, and cards for automatic typewriters.
REFERENCES
Roomets, S. Perfokarty i ikh primenenie. Tallinn, 1965.
Anisimov, B. V., and K. S. Khomiakov. Ustroistva podgotovki dannykh dlia elektronnykh vychislitel’nykh mashin. Moscow, 1972.