Max Newiss and Lloyd Thompson
A 
tracker ball is computer cursor control device. The user can roll the ball to navigate around the screen.
The uses are:
- Controls the movement of a pointer on the screen.
Advantages are:
- They are ergonomic which makes them more comfortable to use.
- For people with wrist or forearm problems who can’t use a mouse.
- On smaller desk space.
Disadvantages are:
- Mainly moulded for right handed people.
- More expensive.
Alternatives are:
- Scroll wheel.
- Mouse.