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Punched tape is an old-fashioned form of data storage, consisting of a long strip of paper in which holes are punched to store data.
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 analog 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.
Punched tape was eventually also used as a way of storing messages for teletypewriters. The idea was to type in the message to the paper tape, and then send the message at "high speed" from the tape. The tape reader could "type" the message faster than a typical human operator, thus saving on phone bills. Text was encoded in two common standards, Baudot which had 5 holes and ASCII which had 7 or 8 holes.
When the first business-oriented computers were being released many turned to the existing mass-produced teletypewriter as a low-cost solution for printer output. This is why computers today still use ASCII. As a side effect the punched tape readers became a popular medium for low cost storage, and it was common to find a selection of tapes containing useful program in most computer installations.
In the late 1960s to early 1970s, Teletype Corporation's ASR33 was a very popular model of teletype. It had a built in paper tape reader and tape punch (8 hole ASCII). It could print and read or punch tape at the speed of 10 characters per second. The ASR33 tape reader was purely mechanical; 8 spring loaded fingers would be thrust into the tape (one character at a time) and an assortment of rods and levers would sense how high the finger rose, which told it if there was a hole in the tape at that position. Later on, photo readers that used light sensors could work in much higher speeds (hundreds of characters per second) and more sophisticated punches could run at somewhat higher speeds (Teletype's BRPE punch could run at 60 characters per second).
"Wikipedia" in ASCII punched tape code (without a parity bit or with "spacing" parity) appears as follows (created by the BSD ppt program):
/\/\/\/\/|
| . |
| . |
| o o .ooo| W
| oo o. o| i
| oo o. oo| k
| oo o. o| i
| ooo . | p
| oo .o o| e
| oo .o | d
| oo o. o| i
| oo . o| a
| o.o o| Carriage Return
| o. o | Line Feed
| . |
| . |
|/\/\/\/\/
The two biggest problems with paper tape were
- Reliability. It was common practice to follow each mechanical copying of a tape with a manual hole by hole comparison. See also chad (the little pieces of paper punched out of the tape).
- Rewinding the tape was difficult and prone to problems. Great care was needed to avoid tearing the tape. Some systems used fanfold paper tape rather than rolled paper tape. In these systems, no rewinding was necessary nor were any fancy supply reel, takeup reel, or tension arm mechanisms required; the tape merely fed from the supply tank through the reader to the takeup tank, refolding itself back into the exact same form as when it was fed into the reader.
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