COMPONENTS OF HARDWARE

I. Input unit: This unit accepts instructions and data.
II. Output unit: This unit communicates the results to the user.
III. Storage unit: This unit stores temporary and final results.
IV. Central Processing Unit (CPU): This unit performs processing of instructions and data
inside the computer.

The CPU has three components:

a) The Control Unit
b) The Arithmetic Logic Unit (ALU) and
c) The Memory Unit.

a) Control Unit:

It controls the overall operation of the computer system. It is considered as the heart of
the computer system. It controls all the other units, directs them to operate in a proper way and
co-ordinates various operations performed.
It instructs the input device to transfer the data and instructions to the main memory and
then to the arithmetic and logic unit (ALU). Then, it sends the processed result from ALU to the
memory unit for storage and transfers it to the visual display unit or to the ' printer.

The control unit coordinates the various parts of the computer system - the arithmetic
logic unit, the memory unit and the peripheral units. Besides, it controls the flow of data into,
from and within the main storage as per the program instructions.
To perform its control operations effectively and quickly, the control unit has four basic
components. They are
(a) Instruction Register
(b) Decoder
(c) Address Register and
(d) Instruction Counter
The instruction register receives one by one the instructions to be executed in the required
sequence. Then, the operation code of the instructions is transferred to decoder, which decodes
the operation code. And it activates the appropriate circuits of the arithmetic and logic unit to
perform the operation. The address register enables the data in the location specified in the
instruction to be transferred to a specified accumulator for the arithmetic and logic unit.

b) Arithmetic Logic Unit (ALU)

This unit performs two kinds of operations, the arithmetic processing and logical
processing. In arithmetic processing it performs all mathematical operations such as addition,
subtraction, multiplication and division. In logical processing, it performs the relational and
logical operations such as comparing larger or smaller values, true or false statements, etc.

c) Memory Unit

This unit holds the intermediate results during the course of calculations and provides the
data as and when required. This internal storage is also called primary memory or main
memory. This memory takes the data from an input device and stores it until the computer is

ready to process it. It also stores processed data and intermediate results. When the processing
is finished, it transfers the results to an output device.