A trackball mouse looks similar to an ordinary mouse but incorporates a rolling (or scrolling) ball that can be up to the size of a golf ball.
By rolling the ball you are moving the cursor on the screen. It is the forefinger rather than the wrist that generates movement on the screen. The larger the ball, the less effort required by the user.
Multi media product demonstrations
To play the multi media clips, you will need Windows Media Player. If you don't have Windows Media Player, you can download a free version from the Windows Download Centre—see our Related Links. Downloading the software can take a while on slow Internet connections. To make the files accessible to as many people as possible, each media file is captioned and the transcript for each file is also available below as an alternative: