Dictionary of Computers - input device

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Device for entering information into a computer. Input devices include keyboards, joysticks, mice, light pens, touch-sensitive screens, scanners, graphics tablets, speech-recognition devices, and vision systems. The input into an electronic system is usually through switches or sensors. Compare with an output device.

Keyboards, the most frequently used input devices, are used to enter instructions and data via keys. There are many variations on the layout and labelling of keys. Extra numeric keys may be added, as may special-purpose function keys, whose effects can be defined by programs in the computer.

The graphics tablet is an input device in which a stylus or cursor is moved, by hand, over a flat surface. The computer can keep track of the position of the stylus, enabling the operator to input drawings or diagrams into the computer. The joystick signals to a computer the direction and extent of displacement of a hand-held lever.

Light pens resemble ordinary pens and are used to indicate locations on a computer screen. With certain computer-aided design (CAD) programs, the light pen can be used to instruct the computer to change the shape, size, position, and colours of sections of a screen image.

Scanners produce a digital image of a document for input and storage in a computer, using technology similar to that of a photocopier. Small scanners can be passed over the document surface by hand; larger versions have a flat bed, like that of a photocopier, on which the input document is placed and scanned.

Input devices that are used commercially – for example, by banks, postal services, and supermarkets – must be able to read and capture large volumes of data very rapidly. Such devices include document readers for magnetic-ink character recognition (MICR), optical character recognition (OCR), and optical mark recognition (OMR); mark-sense readers; bar-code scanners; magnetic-strip readers; and point-of-sale (POS) terminals. Punched-card and paper-tape readers were used in earlier commercial applications but are now obsolete.

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