track ball
The trackball is a peripheral input device for controlling the cursor. Functionally, it corresponds to the computer mouse, with the difference that the trackball's roller ball is moved by hand.
The trackball consists of a smaller or larger ball that can be moved freely in all directions. The ball rotation directly controls the cursor. Functionally, the trackball rotates two rollers in X and Y direction. The rollers provide position information that is periodically queried and processed in absolute or relative values.
Like the computer mouse, trackballs can be equipped with function keys. They are used in laptops, notebooks and smartphones, but also in mice, keyboards and in heavy-duty devices such as game consoles.