Computer hardware refers to the physical equipment used in the computer. It is differentiated from software which refers to the information and data contents stored within the computer system or outside it that is used in operation of the complete computer system.
All computer hardware are composed of four essential components or sub parts. These are central processor (CP), secondary data storage, Input devices, and output devices. CP may be described as the heart or brain of the computer that does the actual computing or processing work of the computer. The CP contains the CPU that performs the arithmetical and other logical operation in the computer and the primary data storage for storing the computer programs and data used during the process of computing. The secondary data storage of the computer is intended to hold additional data beyond what can be accommodated in the primary storage of CP. The most common example of a secondary storage device is the internal hard disk of computer and DVD drive. Input devices of the computer are used for feeding data to the computer from external sources. The common input devices are keyboard, mouse, and scanners. Output devices are used for receiving required data from the computer. Most common output devices are computer monitor and printer. In addition, secondary storage devices with removable storage media such as DVD disk or pen drive are also used as input as well as output devices.