or pressure. Input devices in turn can be categorized based on:

* Modality of output (e.g., mechanical motion, audio, visual, etc.)
* Whether the output is discrete (e.g., pressing of key) 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 CAD applications)