computer terminal

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computer terminal,

a device that enables a computercomputer,
device capable of performing a series of arithmetic or logical operations. A computer is distinguished from a calculating machine, such as an electronic calculator, by being able to store a computer program (so that it can repeat its operations and make logical
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 to receive or deliver data. Computer terminals vary greatly depending on the format of the data they handle. For example, a simple early terminal comprised a typewriter keyboard for input and a typewriter printing element for alphanumericalphanumeric
or alphameric
, the set of letters and numbers. When used in reference to computer input and output, the set usually is expanded to include the upper- and lower-case alphabetic characters (A–Z, a–z), the numeric characters (0–9), and
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 output. A more recent variation includes the keyboard for input and a televisionlike screen to display the output. Liquid crystalliquid crystal,
liquid whose component particles, atoms or molecules, tend to arrange themselves with a degree of order far exceeding that found in ordinary liquids and approaching that of solid crystals.
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 displays, cathode-ray tubescathode-ray tube
(CRT), special-purpose electron tube in which electrons are accelerated by high-voltage anodes, formed into a beam by focusing electrodes, and projected toward a phosphorescent screen that forms one face of the tube.
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, and gas plasma panels (the last involving an ionized gas, sandwiched between glass layers, which glows to form dots which, in turn, connect to form lines) have been used as display screens. Such displays can present a variety of output, ranging from simple alphanumerics to complex graphic images used as design tools by architects and engineers. Portable terminals typically use liquid crystal displays because of their low power requirements. The terminals of pen-based computerspen-based computer,
computer that uses software to enable it to accept handwriting or drawing as a form of input. A stylus, which may contain special electronic circuitry, may be used to write on the computer display or on a separate tablet.
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 use a stylus to input handwriting on the screen. Touch-sensitive terminals accept input made by touching a pressure-sensitive panel in front of a menu displayed on the screen. Other familiar types of terminals include store checkout systems that deliver detailed printed receipts and use laserlaser
[acronym for light amplification by stimulated emission of radiation], device for the creation, amplification, and transmission of a narrow, intense beam of coherent light. The laser is sometimes referred to as an optical maser.
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 scanners to read the barcodesbarcode,
computer coding system that uses a printed pattern of lines and bars to identify such things as products, mail and packages, and customer accounts; the term also is used for similar coding systems that do not use bar-based patterns.
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 on packages, and automatic teller machines in banks.


See L. Tijerina, Video Display Terminal Workstation Ergonomics (1984).