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Glossary » I/O Devices

double click

to click a button twice quickly in succession, typically on a mouse. This is used to indicate that the region currently under the mouse pointer should respond in some way distinct from how it responds to a single click, usually…

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Dvorak keyboard

The most common alternative to the standard QWERTY keyboard; the Dvorak keyboard assigns letters to keys so that typing is fast. Primary alphabetic keys are arranged in three rows as follows:



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electronic ink

in pen-based computing systems, the untranslated scrawls a user makes on a screen, stored as a set of lines or points. Electronic ink may be stored as is, or translated into text or structured graphics for further editing, searching, etc.…

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escape key

a key on the keyboard used to exit a mode. This can apply to moving upwards through a hierarchy of screens or stopping the execution of a program. Also used to break out of a command mode (where typing issues…

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event handler

a central software routine for applications in graphical user interfaces that processes events as they arrive, primarily user input such as keystrokes and mouse clicks, but also system events such as time-based triggers. The events arrive in an event buffer.…

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a range of devices are capable of observing a person’s pupil to determine the direction of their gaze.

Eye-tracking can be used for input, by directly controlling a pointer on the screen, or even for communicating the gaze direction to

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fingertip controls

keys that are activated by touch, without having to actually press them down. These are common, for instance, on microwave ovens because they are easier to clean. They should not be used in all applications because they are easier to…

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Fitts’ Law

T = k log2(D/S + 0.5), k ~ 100 msec.

T = time to move the hand to a target
D = distance between hand and target
S = size of target

Fitts’ Law is a model to…

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flat screen display

or flat panel display (FPD); a screen that is very thin, potentially using a variety of different technologies, such as LCDs and gas-plasma displays. In contrast, because of the need to direct an electron beam across the whole display, CRTs…

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in CRT displays, the screen is rapidly refreshed, generally 50-100 times per second. In between refreshes, phosphors dim, but the human eye will only perceive the average luminance provided that the refresh is frequent enough. Unfortunately, the periphery of our…

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foot pedal

or “mole” (an underground “mouse”); an input device that is controlled by a person’s foot, useful for entering boolean values (up or down) or values along a continuous range. Foot pedals are common in cars, pianos, and sewing machines. From…

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force feedback

the application of physical force in response to user input. Used, for instance, in arcade games and car and plane simulators. A force feedback input device, such as a mouse or joystick, can provide redundant tactile feedback of what’s on…

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frame rate

the speed that an animation or video is displayed, specifically: the number of frames (individual pictures making up the animation or video) that are displayed per unit time. For instance, televisions display 60 frames per second (also called the “refresh…

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an input method commonly used in pen-based systems -or- a physical movement used in communication such as a hand motion or a facial expression.

1. input method – gestures are pen movements that can be recognized as various symbols…

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graphical input device; a piece of hardware for pointing and selecting items on a graphical display, such as a mouse, joystick, tablet, or trackpad.

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light that interferes with viewing a display, especially light reflected from the surface of the display. Glare can be reduced in several ways:

the display can be positioned to avoid glare, generally by placing it perpendicular to other light sources.

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glass teletype

a term used for screen-based terminals (such as a vt100), emphasizing their similarity to a teletype and thus their relatively limited functionality.

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green screen

an informal term for a monochrome computer monitor displaying a character interface (with green phosphor, though common equivalent monitors are amber or black-and-white). Commonly used to indicate that an outdated system is being referred to, especially legacy mainframe or DOS…

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haptic interface

a user interface based on touch, using the movements of the user as input and the sense of touch as output (both tactile and kinesthetic feedback). Examples include force feedback joysticks and Braille screen readers.

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head-mounted display

HMD; a computer monitor or other display (such as an LED readout) that can be worn on the head so that a user can view it without looking away from the surrounding environment and without having to hold the display,…

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hot-swappable device

any hardware input or output device that can be plugged into a computer or removed from it while the computer is “hot”, turned on and currently running software, so that the device can be detected and used by software and…

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hue-saturation-value; a color model that specifies any given color based on its hue (the frequency of light, e.g. red-orange-yellow-green-blue-violet), saturation (amount of white versus pure color), and value (intensity or brightness). Formally equivalent to other color models (RGB, HSB, CMYK),…

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resistance to applied force, e.g. viscosity. Applied to keyboard keys and the feel of resistance they give, and appropriate to all interactions where the interface resists change, lags in response, or dampens the magnitude of the input (e.g. an icon…

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input device

the way a person talks to a computer; a piece of hardware used for entering information into a computer, including commonly used peripherals like keyboards, mice, and joysticks, but also including microphones and even eye movement devices.

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displaying images by drawing only a partial image first, consisting of alternate lines, or every 3rd or 4th line, then filling in the remaining lines progressively. When images are displayed slowly, such as large gifs slowly downloading off the internet,…

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