Information and Communication Technology

Basic Components of a Computer

Although computers differ widely in their details, all of them follow a basic organisational structure as shown in the figure below.

In order to carry out the basic three operations, namely, input, process and output, a computer includes the following hardware components:

1. Input unit
2. Processing unit
3. Output unit
4. External storage unit

Input unit

An input unit presents data to the processing unit in machine-readable form. Although the keyboard is a common input unit for a small computer, a system may also support one or more of the input units.

Processing unit

Processing units receive data and instructions, store them temporarily and then process the data as per the instructions. The processing units include:

1. Memory unit (MU)
2. Arithmetic logic unit (ALU)
3. Control unit (CU)

All the three units together is known as the central processing unit (CPU)

Output unit

Output devices receive information from the CPU and present it to the user in the desired form. Although a printer is the most commonly used output unit, devices such as plotters are also becoming popular.

External storage unit

The purpose of external storage is to retain data and programs for future use. For example, a program may be required at regular intervals. If such information is stored in an external storage media, then one can retrieve it as and when necessary, thus avoiding repeated typing. Any number of files containing information can be stored on external media. Since they are permanent (they are not erased when the power is turned off) we can store long files on external media, and later on work on them in sections, keeping all the sections in storage except the one currently in use.