ticker tape
| Storage medium ticker tape
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 5-channel punched tape with up to 5 holes in each column for data bits . |
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| General | |
|---|---|
| Type | mechanical storage medium |
| size | Widths 17.4 mm or 25.4 mm |
| origin | |
| Launch | 18th century |
A punched tape is a strip-shaped data carrier made of paper , plastic or a metal-plastic laminate , the information of which is represented by punched holes. The principle corresponds to a punch card with a variable length.
history
As early as the 18th century, punched strips , here strung together wooden plates, were used to control looms . Even in the 21st century, such looms with metal link strips are still in use in tartan weaving mills .
With barrel organs, piano rolls with a similar principle also serve as information carriers to this day . They are read out pneumatically, and their perforations are partly analog in that a long tone is simply created through an elongated hole.
The punched tape has also been used to display and store data since the middle of the 19th century . Initially, they were used in data transmission by telegraphs . In this Morse points (short signals) z. B. encoded by vertically one above the other holes, bars (long signals) through diagonally arranged holes.
In 1841 Charles Wheatstone constructed a punching telegraph in London with the Wheatstone punched tape code attached to the left and right of a central transport lane. The first use of punched tapes in Germany was in telegraphs from Siemens, and in 1869 Jaite built a receiver punch in Berlin.
The punched tapes still known today are used as a storage medium for teleprinters and computers . They are also used in the numerical control of machine tools.
The punched tape is the forerunner of the punched card as a data storage medium. The punch card as a data storage medium was first used by the state administration in the USA in 1890 for the census by Herman Hollerith .
Before the advent of magnetic storage media such as magnetic tape and magnetic disk, punched tapes and similar mechanical storage systems such as punched cards were the most economical readable and writable data carriers . Due to their robustness, easy handling and widespread use, as well as the fact that they can be read with the naked eye if necessary, punched tapes are still used to a small extent at the beginning of the 21st century. B. used in military communications. However, they have lost their importance in the computer sector.
In concrete terms, punched tapes were used in a variety of ways in computer technology: for program source texts , for compiled binary code , for data sets and often as control strips for peripheral devices . A specific working day for a programmer then looked like he would type in a program on a teleprinter (or later punched tape terminal), then create another punched tape with a data record and then go to the computer. There he read in the ready-made compiler in the form of a hard-wearing plastic punched tape, then his program punched tape and after starting the program the data strip. The computer then produced a result paper tape that was either printed out in plain text on the telex or, if it was a control tape, for example to go into another room, where there was a desk- sized plotter that accepted this paper tape as input and a diagram produced. The punched tapes were often used in different colors depending on their purpose.
On the other hand, if the program had errors, they had to be fixed . Punched tapes had a particular advantage here: they could be corrected by hand to a limited extent. When it came to individual characters to be corrected, you could sometimes even add individual holes with a hand punch ; Any characters could be eliminated in the Baudot code by a Bu character (all 5 holes) or in the ASCII code by a DEL character (all 7 holes), but only in rare cases replaced by another character. For larger changes you only had to insert sequences of pure transport perforation at reasonable intervals, which normally corresponded to an unused code "zero". Then you could cut in these places with scissors and insert a corrected piece by gluing with black tape (for optical scanning). The programming tool (or cutlery ) that you had to bring with you then consisted of straight paper scissors, a roll of black adhesive tape and a felt-tip pen to write on the finished tape.
Technical
Tape punch
To write on a perforated strip, punching devices are used that have a bar of punching heads at right angles to the direction of travel. For each character to be stored, a column of the perforated tape is punched with a corresponding pattern . The guide hole is always punched out. Then the strip is continued one position and the next character is written. Punching devices on a teleprinter typically punch 6 2/3 characters (rows of holes) per second, newer punching devices reach speeds of up to 150 characters per second.
Paper tape reader
The perforated tape can be scanned in different ways: mechanically, electrically, optically or electrostatically.
With mechanical scanning , the strip is transported character by character by means of a spiked wheel reaching into the guide holes and the holes are scanned with mechanical sensors whose arrangement corresponds to the punching heads of the pen. The mechanical reading devices, which are mostly associated with teleprinters , also typically work at a speed of 6 2/3 characters per second.
The electric tape reader has a number of contact pins that replace the mechanical feeler levers . The punched tape is guided over the pins, which can only close a contact if a hole has been punched out in their respective position. As with the mechanical punched tape reader, the tape is guided by a spiked wheel. Electric readers reach higher speeds than mechanical ones.
Instead of the sensor arms or contact pins, optical reading devices use a number of light barriers for the data holes and the guide hole, which here is only used for data synchronization (strobe pulse). The strip is transported by means of a capstan drive; there are also optical punched tape readers that have a brake so that the strip can be started and stopped very quickly (stopping at full speed without overflowing another hole). The speeds of optical tape readers are over 1000 characters per second; the fastest commercially available reader came from the Danish manufacturer A / S Regnecentralen with 2000 characters per second.
The punched tapes were not rewound immediately after they were read in, but were instead, especially with very long punched tapes, caught in special baskets and only wound onto spools after processing with rewinders.
Punched tape formats
There are two mechanically compatible strip formats (picture) : The punched tape used in telex and early computer technology is 17.4 mm wide and has 5 parallel data hole positions plus a smaller guide hole between data holes 3 and 4. The data holes are arranged in a square grid of 2.54 mm = 1/10 inch. The punched tapes, which were later mainly used in computer technology, have a width of 25.4 mm and have 8 data hole positions. As with the first format mentioned, the guide hole is between hole 3 and 4. In both formats, 10 characters (rows) are punched onto one inch (25.4 mm) punched tape. The two punched tape formats are congruent in the width of the narrower strip when they are placed one on top of the other. This means that a 5-channel strip can often be scanned in an 8-channel reader without any problems (at least if the reader uses the guide holes to guide the strip - which is usually not the case with optical readers). It doesn't work the other way around. There are also devices that can punch both strip widths by adjusting the strip guide.
256 different characters can be stored on an 8-channel punched tape, initially only 32 on a 5-channel punched tape . With the Baudot code , two special control characters can be used to switch between two code halves, so that a total of 59 effective characters can be encoded.
In addition, there are different methods for longer punched tapes: In most cases they are wound onto spools like older analog films with very similar mechanics to those used there , but a kind of fan-fold was also common at the manufacturer DEC .
literature
- H. Pärli et al., Hans Konrad Schuff (editor): The punched tape in information processing systems . Ed .: Mathematical Consulting and Programming Service, Dortmund. Friedr. Vieweg & Sohn, Braunschweig 1964, ISBN 978-3-322-96063-4 ( limited preview in the Google book search [accessed October 10, 2019]).
Web links
- Article about punched tape in the lexicon of a support association for technology
- Perforated tape technology (= perforated tape technology), Robotron, GDR
- Text-Baudot-Code converter with punched tape
- VIDEO about punching and reading punched tape on robotron-computermuseum.efb-1.de
Individual evidence
- ↑ Wilfried de Beauclair : Calculating with machines . A pictorial history of computing technology. Springer Fachmedien, Wiesbaden 1968, ISBN 978-3-663-00809-5 , p. 57 ( limited preview in Google Book Search [accessed October 10, 2019]).
- ↑ On the other hand, sealing excess holes was more complex and only possible with later versions of hand punching, in which a black adhesive film was glued over the entire width of the strip and then all further holes required were punched by hand.
- ↑ Data sheet and illustration of the RC 2000 punched tape reader (English)
- ↑ ECMA-10 standard , see Chapter 2