Computer is an electronic device, which can deal both arithmetical and logical operation. Even though the size, shape, performance, reliability and cost of computers have been changing over the years. All computer systems perform the following five basic operations for converting raw input data into useful information and presenting it to a user:

Inputting Process of entering data and instructions into a computer system.

Storing Saving data and instructions to make them readily available for initial or additional processing as and when required.

Processing Performing arithmetic operations (add, subtract, multiply, divide etc.) or logical operations (comparisons like equal to, less than, greater than, etc.) on data to concert them into useful information. Outputting Process of producing useful information or results for a user, such as printed report or visual display. Controlling Directing the manner and sequence in which the above operations are performed.

OUTPUT DEVICES

Output devices perform the reverse operation of that of an input device. It supplies information obtained from data processing to outside world. Hence, it links a computer with its external environment. As computer work with binary code, results produced are also in binary form. Therefore, before supplying the results to outside world, the system must convert them to human acceptable form. Units called out put interfaces accomplish this task. Output interfaces match the unique physical or electrical characteristics of output devices to the requirements of an external environment.

An output unit performs following functions;

1. It accepts the results produced by a computer, which are in coded form and hence, we

cannot easily understand them.

2. It converts these coded results to human readable form.

3. It supplies the converted results to outside world. There are three types of output:

1. Hard copy output.

2. Soft copy output.

3. Audio output.