Trackball and Thumbwheel:

Joysticks

A joystick contains a small, vertical lever (called the stick) mounted on a base that is utilized to steer the screen cursor around. Some joysticks are mounted on keyboard. Most joysticks select screen situated with actual stick movement; while a few respond to the pressure on the stick.

The distance moved by the stick in any direction from its center position and the distance of the screen cursor movement in this direction are proportionate. Potentiometers mounted at the base of the joystick are utilized to measure the amount of movement, and the stick returns to the centre position when it is released because of the spring. One or more buttons can be programmed to work as input switches to signal certain actions once a screen position has been selected.

In another type of movable joystick, the stick is utilized to activate switches that cause the screen cursor to move at a constant rate in the decided direction. Eight switches, arranged in a particular circle, are sometimes provided, so that the stick may select any one of eight directions for cursor movement.