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(punched tape, perforated tape), a recording medium in the form of a paper, celluloid, or polyethylene-terephthalate (lavsan) tape on which data are recorded by the punching of holes. The most common types of punch tape are made of strong paper about 0.1 mm thick and have widths of 17.5, 20.5, 22.5, or 25.4 mm. The tape’s width and thickness and the shape and arrangement of the holes are usually determined by the material from which the tape is made and the design of the punch. Punch tape has from five to eight longitudinal data-representing rows and, usually in the middle, an additional row of continuous small transport holes. The number of rows corresponds to the number of code elements (bits) that are simultaneously recorded on or read from the tape.
Data are recorded on the punch tape by mechanical or electromechanical punches at speeds up to 300 lines/sec. The reading of data is carried out by electromechanical tape readers or through the use of photoelectric cells at speeds up to 3,000 lines/sec. Punch tape is used for long-term storage and multiple reproduction of information. Punch tape is not as strong as punch cards, but units that use punch tape are usually simpler and cheaper than punch-card units and can operate at higher speeds. Data entered on punch tape are accessible for reading without special devices, which is not true of magnetic tape. Punch tape, however, can be used for only one recording. It is difficult to correct data that have been entered on punch tape, and splicing of the tape greatly diminishes its mechanical properties. Punch tape is used in computers for data input and output and also in high-speed telegraph devices, automatic typewriters, and industrial installations and plants with program control.
Punch tape made of ordinary cinematographic film (darkened beforehand) is less common; it has been used for the most part in the data input devices of certain computers. In the 1960’s, punch tapes on a polyethylene-terephthalate base came into use abroad and in the USSR; the strength of such tapes is much greater than that of paper tapes.
REFERENCESSedláč ek, J., and K. Ŝtĕ tka. Perfolenta. Moscow, 1964. (Translated from Czech.)
Anisimov, B. V., and K. S. Khomiakov. Ustroistva podgotovki dannykh dlia elektronnykh vychislitel’nykh mashin. Moscow, 1972.
D. P. BRUNSHTEIN