Punched tape

A paper tape is an existing paper, plastic, or metal-plastic laminate strip-shaped volume whose information is represented by punched holes. The principle is a punched card with variable length.

History

Already in the 18th century were punched tape, strung together wooden plates for control of looms used here. Even in the 21st century are those looms, with flexible metal strip, still in tartan weaving in use.

In barrel organs serve up today piano roll with the same principle as an information carrier. You will read pneumatic, and their holes are partially analog, by a long beep is generated simply by an elongated hole.

The tape used since the mid 19th century, and the presentation and storage of data. Initially, they were used in data transmission by telegraph. In this common Morse dots ( short signals ) eg by a vertical line standing holes, dashes ( long signals) through diagonal holes arranged coded ( Wheatstone Tape code ). The present-day concept paper tape can be used as a storage medium for teletype and computer. Also in the numerical control of machine tools, they are used.

The tape is the precursor of punch card for data storage. The punch card for data storage was first used in 1890 by the state administration in the United States in the census by Herman Hollerith.

Tape and similar mechanical storage systems such as punch cards were before the advent of magnetic storage media such as magnetic tape and magnetic disk the most economical readable and writable disk. Due to its robustness, ease of use and wide distribution, and the fact that they can be read with the naked eye if necessary, paper tape are used to a small extent at the beginning of the twenty-first century, for example, in military communications. For computers, however, they have lost their meaning.

Specifically tape were used varied in computer technology. For program source code, compiled for Binary Code, for records and often as a control strip for peripherals A concrete working for a programmer looked like this that he. At a teletype (or later tape Terminal) typed in a program, then created another tape with a record that will eventually went to the computer There he read the lying ready compiler in the form of a durable plastic punched tape a, then its program tape and after the start of the program, the data stripes. The computer then produced a result punched tape, which you printed out either in clear text on telex or if it was a control tape, so that, for example, went into another room where a desk large plotter stand, which accepted this tape as input, and a diagram produced.

If the program, however, had errors, you had to clean them up. This paper tape offered a special advantage: they were corrected within limits by hand. When it came to single incorrect character, you could sometimes even add a single hand punch holes; any character could be eliminated (all 7 holes) in the Baudot code by a Bu characters (all 5 holes ) or in ASCII code by a DEL character, replace but only in rare cases, by another character. For larger changes, you just had at reasonable intervals sequences of pure sprocket holes to insert, which is normally an unused code " null" corresponded. Then you could cut it into these locations with a pair of scissors and paste a corrected piece by gluing with black tape (for optical scanning). The programming tool ( or cutlery ), which you had to bring, then consisted of a straight paper scissors, a roll of black tape and a felt pen to label the finished hole strip.

Technical

Paper tape punch

To write a paper tape punch units are used, the running direction have a bar of punching heads at right angles. For each character to be stored one column in of the tape is bestanzt with a corresponding pattern. The Hole is getting punched. Thereafter, the strip is further guided to a position written and the next character. Punching devices on a teletype punch typically 6 2/ 3 characters ( rows ) per second, newer punching devices reach speeds of up to 150 characters per second.

Tape reader

The scanning of the punched tape can be done in several ways: mechanical, electrical, optical or electrostatic.

In the mechanical scanning of the strip is transported sign by means of a cross into the guide holes spiked wheel and the holes sampled with mechanical probes that correspond to the punching heads of the pen in their arrangement. The mechanical readers that are associated with teletypes usually also typically operate at a speed of 6 2/ 3 characters per second.

The electrical tape reader has a number of pins, replace the mechanical lever type. The tape is passed over the pins, which can only close a contact when at their respective position, a hole is punched. The strip guide is accomplished as the mechanical tape reader on a thorn cog. Electrical readers achieve higher speeds than mechanical.

Optical readers use instead of the sensor arms or pins a series of photoelectric sensors for data holes and the guide hole only for data synchronization ( strobe ) is used here. The strip is transported via a capstan drive, there are also optical tape reader, which have a brake to start the strip very quickly and can stop ( stop from full speed without another hole to run ). The velocities of optical paper tape reader be more than 1000 characters per second; the fastest commercially available readers came from the Danish manufacturer A / S Regnecentralen with 2000 characters per second.

Tape formats

There are two mutually mechanically compatible strip formats: The commonly used remote writing technique and early computer art paper tape has a width of 17.4 mm and has 5 parallel data hole positions plus a smaller guide hole between data hole 3 and 4. Data holes are arranged in a square grid of 2,54 mm = 1/10 inch. The later mainly widespread in computer technology hole strips have a width of 25.4 mm and equipped with 8 data hole positions. The Hole is located here as in the former format between hole 3 and 4 are in both formats on one inch (25.4 mm) hole strip 10 characters ( rows ) punched. The two tape formats are in when they are superimposing congruent in the width of the narrower strip. Thus, a 5 channel strips often be easily scanned in an 8 -channel reader ( at least if the reader used the guide holes for guiding the strip - which in optical readers usually not the case). Conversely, you can not. There are also devices that can punch both strip width by adjusting the tape guide.

On an 8 -channel tape 256 different characters can be stored on a 5 -channel paper tape initially only 32 When Baudot code can be switched via two special control characters between two code parts so that a total of 59 active characters can be encoded.

In addition, there are different methods for longer tape: In most cases, they are wound as older analog films with very similar mechanics as there on reels, specially from the manufacturer DEC but was also a kind of fan-fold normal.