A computer is a machine that operates as per a list of instructions to manage data. In 1837, Charles Babbage designed the Analytical engine which was a programmable mechanical computer. In the U.S. census in 1890, tabulating machines were manufactured by the Computing Tabulating Recording Corporations for data processing of punched cards. The five early digital computers wee Zuse Z3, Atanasoff-Berry computer, Colossus, Harvard Mark I IBM ASCC and ENIAC.

The parts of a computer are the Arithmetic and Logic unit, the Control unit, the memory, the input devices and the output devices. These are interconnected by buses. The control system reads and decodes the instructions in the program and generates a series of signals directed at the other parts of the computer. The Arithmetic and Logic unit performs operations like addition, subtraction, multiplication etc as well as AND, OR, XOR, NOT functions. The memory is a list of cells where numbers can be stored or read. Every cell can store only one number and has an address.

The arithmetic and logic unit, control unit, registers and basic input/output are together known as the central processing unit. This unit has a special set of memory cells called registers. Here, information can be read and written faster. The computer memory is of two types Read Only Memory or permanent memory and Random Access Memory or temporary memory. When the power of the computer is turned off, the contents of the temporary memory are erased, while that of the permanent memory is retained. Some input devices are keyboard and mouse. Output devices are display and printer. Hard disk drives, floppy disk drives and optical disc drives can be used both for input and output.

Hardware refers to the external parts of a computer. Software means a set of programs. A program is a set of instructions within the computer and can include several languages.

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