One type of paper tape punch
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.
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 holes ("sprocket holes") that were always punched served to feed the tape, typically with a wheel with radial pins 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.
The word "Wikipedia" as 7-bit ASCII (without a parity bit or with "space" parity)
Most tape-punching equipment used solid punches to create holes in the tape. This process inevitably creates "chads", or small circular pieces of paper. Managing the disposal of chads was an annoying and complex problem, as the tiny paper pieces had a distressing tendency to escape and interfere with the other electromechanical parts of the teleprinter equipment.
One variation on the tape punch was a device called a Chadless Printing Reperforator. This machine would punch a received teleprinter signal into tape and print the message on it at the same time, using a printing mechanism similar to that of an ordinary page printer. The tape punch, rather than punching out the usual round holes, would instead punch little U-shaped cuts in the paper, so that no chads would be produced; the "hole" was still filled with a little paper trap-door. By not fully punching out the hole, the printing on the paper remained intact and legible. This enabled operators to read the tape without having to decipher the holes, which would facilitate relaying the message on to another station in the network. Also, of course, there was no "chad box" to empty from time to time. A disadvantage to this mechanism was that chadless tape, once punched, did not roll up well, because the protruding flaps of paper would catch on the next layer of tape, so it could not be rolled up tightly. Another disadvantage, as seen over time, was that there was no reliable way to read chadless tape by optical means employed by later high-speed readers. However, the mechanical tape readers used in most standard-speed equipment had no problem with chadless tape, because it sensed the holes by means of blunt spring-loaded sensing pins, which easily pushed the paper flaps out of the way.
Paper tape relay operation at FAA's Honolulu flight service station in 1964
Punched tape was used as a way of storing messages for teletypewriters. Operators typed in the message to the paper tape, and then sent the message at the maximum line speed from the tape.
This permitted the operator to prepare the message "off-line" at the operator's best typing speed, and permitted the operator to correct any error prior to transmission. An experienced operator could prepare a message at 135WPM (Words Per Minute) or more for short periods.
The line typically operated at 75WPM, but it operated continuously. By preparing the tape "off-line" and then sending the message with a tape reader, the line could operate continuously rather than depending on continuous "on-line" typing by a single operator. Typically, a single 75WPM line supported three or more teletype operators working offline.
Tapes punched at the receiving end could be used to relay messages to another station. Large store and forward networks were developed using these techniques.
Software on paper tape for the Data General Nova minicomputer.
When the first minicomputers were being released, most manufacturers turned to the existing mass-produced ASCII teletypewriters (primarily the ASR33) as a low-cost solution for keyboard input and printer output. As a side effect punched tape became a popular medium for low cost storage, and it was common to find a selection of tapes containing useful programs in most minicomputer installations. Faster optical readers were also common.
In the 1970s, computer-aided manufacturing equipment often used paper tape. Paper tape was a very important storage medium for computer-controlled wire-wrap machines, for example. A paper tape reader was smaller and much less expensive than hollerith card or magnetic tape readers. Premium black waxed and lubricated long-fiber papers, and PET film "paper" tape were invented so that production tapes for these machines would last longer.
Paper tape was the basis of the Vernam cipher, invented in 1917. During the last third of the 20th century, the U.S. National Security Agency used punched paper tape to distribute cryptographic keys. The 8-level paper tapes were distributed under strict accounting controls and were read by a fill device, such as the hand held KOI-18, that was temporarily connected to each security device that needed new keys. NSA has been trying to replace this method with a more secure electronic key management system (EKMS), but paper tape is apparently still being employed.
Fanfold paper tape.
The three 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.
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.
Low information density. Datasets much larger than a few dozen kilobytes are impractical to handle in paper tape format.
Paper tape does have some useful properties:
Longevity. Although many magnetic tapes have deteriorated over time to the point that the data on them has been irretrievably lost, punched tape can be read many decades later, if printed on Acid free paper. Some paper can rapidly degrade.
Human accessibility. The hole patterns can be decoded visually if necessary, and torn tape can be repaired (using special all-hole pattern tape splices). Editing text on a punched tape was achieved by literally cutting and pasting the tape with scissors, glue, or by taping over a section to cover all holes and making new holes using a manual hole punch.
Magnetic field immunity. In a machine shop full of powerful electric motors, the numerical control programs need to survive the magnetic fields generated by those motors.
Punched tape in art
A computing or telecommunications professional depicted in the Monument to the Conquerors of Space in Moscow (1964) holds what appears to be a punched tape with three rows of rectangular holes.
Chad (the little pieces of paper punched out of the tape).
Zygalski (Perforated) sheets - a system used to decrypt messages enciphered on German Enigma machines.
Wikimedia Commons has media related to: Papertape
^ Microprocessor-based Control Systems by Naresh Kumar Sinha Page 264: "Paper tape is well suited to a machine shop environment whereas magnetic tape may be accidentally erased or contaminated by foreign substances. ... Other disadvantages of paper tape are as follows ..."
^ "computer programming punch paper tape": "Factory computer numerical control (CNC) equipment used paper tape well into the 1980s"
ECMA-10: ECMA standard for Data Interchange on Punched Tape
A song mentioning paper tape
Various punched media
Friden Flexowriter combination typewriter, paper tape punch, and paper tape reader, designed by IBM during the 1940s and bought out by Friden in the late 1950s (Retrieved April 10, 2007)
Detailed description of two paper tape code systems, Baudot code and the system used by the ILLIAC computer
Paper data storage media
Writing on papyrus (c.3000BCE) Paper (105CE)
Punched tape (1846) Book music (1863) Ticker tape (1867) Piano roll (1880s) Punched card (1890) Edge-notched card (1896) Optical mark recognition Optical character recognition (1929) Barcode (1948) Paper disc (2004)
Categories: Computer storage tape mediaHidden categories: Articles lacking sources from November 2009 ; All articles lacking sources
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