LIS 505 - Input and output

input devices

Machines that feed data into a computer.


Sets of typewriter-like keys that enable users to enter data and commands into computers.

pointing devices

Devices with which users can control the position of the pointer on the screen.


Pointing devices that users roll around a hard, flat surface. Mice may be mechanical (containing a ball and mechanical sensors), optomechanical (containing a ball and optical sensors), or optical (using a laser to detect movement). Mice may connect to computers via serial ports, PS/2 mouse ports, or USB ports. Cordless or wireless mice use infrared or radio waves to communicate with the computer instead of physical wires.


Pointing devices like upside-down (opto)mechanical mice, in which users manipulate the ball directly.


Pads over which users move a finger or other object to control the pointer.

pointing sticks

Pointing devices like miniature joysticks, usually with a rubber tip and positioned among the keys of a keyboard.


Lever pointing devices. The more the lever is tilted in any direction, the faster the pointer moves in that direction.

digitizing tablets

More precise devices than touchpads, used for entering drawings. A tablet has either an electronic stylus (or "pen"), or a puck (or "cursor") containing a window with crosshairs. Also called digitizers, graphics tablets, touch tablets, or tablets.

touch screens

Display screens covered with touch-sensitive panels.

light pens

Devices that use a light-sensitive detector to select points on a display screen.

bar code readers

Devices that use a laser to read bar codes and translate them into digital form.

OCR devices

Devices that perform optical character recognition, that is, translate images of text from paper into character code.

MICR readers

Devices that perform magnetic ink character recognition, by magnetizing characters printed in special ink and reading the resulting magnetic patterns.


Devices that read printed text or pictures and translate them into digital form.

flatbed scanners

Scanners with a flat surface on which to lay documents to be scanned.

sheet-fed scanners

Scanners that feed each sheet of paper across a nonmoving scan head. ComputerUser

handheld scanners

Scanners that are held in the hand and passed across the image to be scanned. ComputerUser

digital cameras

Cameras that store images digitally.


Devices that change sound into electronic signals. A sound card usually has a jack into which a microphone can be plugged.


Symbols that appear on the screen indicating where input will be applied. GUIs typically have at least two types of cursor: a pointer (also called the mouse cursor), which indicates where the next mouse action (clicking or dragging) will apply, and an insertion point (also called the text cursor or caret), which indicates where the next character (or other object) will be inserted in a text.

voice recognition

Recognition of spoken words either spoken separately (discrete speech) or in continuous speech. Also known as speech recognition.

output devices

Machines that can present data from a computer.

soft copy devices

Devices that produce soft copy, electronic output, rather than obvious physical objects such as printouts.

video adapters

Adapter boards that allow a computer to produce video output for a monitor. Also called video cards, video boards, video display boards, graphics cards, graphics adapters, and graphics adapter boards.


Devices dedicated to video display, containing a display screen.
CRT monitors
Monitors that use a CRT (cathode ray tube), in which an electron beam moves across the screen from behind.
LCD monitors
Monitors that use liquid crystal display, in which electric currents cause liquid crystals to align so that polarized light does, or does not, pass through them. Nearly all flat-panel displays are LCD. Color LCDs may be either active-matrix, which uses thin-film transistor (TFT) technology, or passive-matrix, covering several different technologies. Passive matrix systems are cheaper than active matrix, but were not perfected as early.
refresh rate
Rate at which a monitor refreshes its display (which is required for displays, such as CRTs, where the contents disappear quickly if not refreshed). Normally measured in hertz (Hz) (refreshes per second), with the standard value being 75 Hz. Also called vertical frequency, vertical scan rate, frame rate, vertical refresh rate, or scan rate.
screen resolution
Number of pixels displayed on a screen. Normally measured as pixels across x pixels down (e.g., 640x480). A monitor cannot display at a higher resolution than its total number of like-colored dots.
dot pitch
Diagonal distance between like-colored dots on a display screen. Normally measured in millimeters. The lower the dot pitch, the sharper the image appears. Also called phosphor pitch.

sound cards

Printed circuit boards that enable a computer to manipulate and output audio signals. A typical sound card can generate audio signals from both waveform and MIDI data and accept input from a microphone. For users to hear the sounds, the audio signals must be translated by a device such as a loudspeaker.
Short for musical instrument digital interface. A standard for controlling devices, such as synthesizers and sound cards, that play music. MIDI representations include note pitch, length, and volume, and sometimes other information.

hard copy devices

Devices that produce printouts or other durable, human-readable records.


Devices that print text or images on paper.
impact printers
Printers that work by striking something against an inked ribbon.
dot-matrix printers
Impact printers in which pins are struck against the ribbon to produce patterns of dots on the page.
non-impact printers
Printers that do not work by striking against a ribbon.
laser printers
Printers in which a laser beam alters electrical charges on a drum, the drum is rolled through toner, which is picked up by the charged portions of the drum, and the toner is transferred to paper through heat and pressure.
ink-jet printers
Printers that work by spraying ionized ink, which is directed by magnetized plates.

portrait mode
A paper orientation in which the page is taller than it is wide.
landscape mode
A paper orientation in which the page is wider than it is tall.
Short for dots per inch. A measure of the resolution of a printer.
Short for pages per minute. A measure of the speed of a printer, based on printing text.

speech synthesis

Production of audio output resembling human speech, usually from text files. Also called voice synthesis.


Devices that allow two-way communication between a user and a computer, typically including a keyboard and a display screen.

point-of-sale terminals

Terminals that serve as cash registers and include other functions such as recording customer orders, processing credit and debit cards, connecting to other systems in a network, and managing inventory. Also called POS terminals.

Last updated October 29, 2002.
This page maintained by Prof. Tim Craven
E-mail (text/plain only):
Faculty of Information and Media Studies
University of Western Ontario,
London, Ontario
Canada, N6A 5B7