Input device

In computing, an input device is a peripheral (piece of computer hardware equipment) used to provide data and control signals to aninformation processing system such as a computer or other information appliance. Examples of input devices include keyboards, mice,scanners, digital cameras and joysticks.

Many input devices can be classified according to:

• modality of input (e.g. mechanical motion, audio, visual, etc.)
• whether the input is discrete (e.g. key presses) or continuous (e.g. a mouse's position, though digitized into a discrete quantity, is fast enough to be considered continuous)
• the number of degrees of freedom involved (e.g. two-dimensional traditional mice, or three-dimensional navigators designed for CADapplications)

Pointing devices, which are input devices used to specify a position in space, can further be classified according to:

• Whether the input is direct or indirect. With direct input, the input space coincides with the display space, i.e. pointing is done in the space where visual feedback or the pointerappears. Touchscreens and light pens involve direct input. Examples involving indirect input include the mouse and trackball.
• Whether the positional information is absolute (e.g. on a touch screen) or relative (e.g. with a mouse that can be lifted and repositioned)