The internal primary memory is volatile and has less storage capacity. Thus, the primary memory is unsuitable for storing large amount of data for a longer period of time. The solution to these limitations is found in the use of secondary storage. It holds information on a more permanent basis for future reference. It is used for storing backups, or copies of data and programs so that they are not permanently lost if power supply is terminated.

The device that supplies information and sends the results of combination to the outside world is called an output device. The two broad classes of output devices are : soft copy output and hard copy output.

All the physical parts or tangible components of computer which can be touched and felt is known as computer hardware. E.g. Keyboard, monitor, RAM, hard disk etc.

Trackball is a stationary pointing device that contains a movable ball rotated with a finger or palm . It consists of a ball resting on two rollers at right angles to each other, which translate the ball's motion into vertical and horizontal movements on the screen.

Mouse is a pointing input device which is used to point & move cursor around the screen & select GUI objects. Computer mouse enables the user to :

• Point to items in lists.
• Draw freehand shapes on a screen.
• Point to icons or tiny pictures that identify processing choices.

The device that collects the input and sends it to the computer is called an input devices. The most common input devices are keyboard, pointing devices, scanners, web camera, digital camera, audio, and video input devices.