Computer trackball and keyboard. View of an Apple Powerbook computer, showing the trackball (mouse device) and part of the keyboard. Like the hand- operated mouse of other computers the trackball is a more compact version used in small handheld or laptop computers. As the ball is rotated, electronic detectors pick up the ball's movements and translate them into corresponding movements of a pointer or other icon on the computer screen. The trackball makes it possible for novices to use computer programs without having to enter complex codes on the keyboard.