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.

The system of using more than one processor to solve a particular problem at the same time is called as parallel processing.

Cache memory is a high speed memory that hold frequently accessed to data or program instructions for the purpose of speeding a computer system's performance.

Primary memory is a computer that is directly accessible to the central processing unit of a computer. The function of primary memory is to store :

1. The operating system programs that manage the operations of the computer.
2. The application program that is being used at the time.
3. The data that is being used by the application program.
4. The output produced by processing.

Random Access Memory is a high speed memory that holds a copy of the operating system, currently executing programs, and other information being processed . It is called a random-access memory because of its ability to access each bytes of data directly.