LOGICAL INPUT DEVICES

STRING DEVICE: provides a string of characters.
-- E.g., Keyboard.

LOCATOR DEVICE: returns a location (x,y,z) in the world coordinates.
-- E.g., Mouse or Trackball.
-- In OpenGL, the located provides a position in screen coordinates, which may have to be tranformed.

PICK DEVICE: returns the identifier of an object.
-- Usually same physical device as locator.
-- In OpenGL, the process is called selection

CHOICE DEVICE: returns one of several options.
-- E.g., a menu selection.

DIAL DEVICE: analog input of real numbers.
-- E.g., slidebar.

STROKE DEVICE: returns an array of locations.
-- Similar to a locator device, but perhaps the beginning and end of stroke is signaled by the press and release of mouse button.