Punched tape

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Punched tape or paper tape is a largely obsolete form of data storage, consisting of a long strip of paper in which holes are punched to store data. It was widely used during much of the twentieth century for teleprinter communication, and later as a storage medium for minicomputers and CNC machine tools.



The earliest forms of punched tape come from [weaving] looms and embroidery, where cards with simple instructions about a machine's intended movements were first fed individually as instructions, then controlled by instruction cards, and later were fed as a string of connected cards. (See Jacquard loom).

This led to the concept of communicating data not as a stream of individual cards, but one "continuous card", or a tape. Many professional embroidery operations still refer to those individuals who create the designs and machine patterns as "punchers", even though punched cards and paper tape were eventually phased out, after many years of use, in the 1990s.

In 1846 Alexander Bain used punched tape to send telegrams.

Tape formats

Data was represented by the presence or absence of a hole in a particular location. Tapes originally had five rows of holes for data. Later tapes had 6, 7 and 8 rows. A row of narrower sprocket holes that were always punched served to feed the tape, typically with a wheel with radial teeth called a sprocket wheel. Text was encoded in several ways. The earliest standard character encoding was Baudot, which dates back to the nineteenth century and had 5 holes. Later standards, such as Teletypesetter (TTS), Fieldata and Flexowriter, had 6 holes. In the early 1960s, the American Standards Association led a project to develop a universal code for data processing, which became known as ASCII. This 7-level code was adopted by some teleprinter users, including AT&T (Teletype). Others, such as Telex, stayed with Baudot.

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