Functional units of computer

1.4 Block Diagram and functional units of 

computer

o Following are the components of computer:

1. Input Unit

2. Output Unit

3. Storage Unit

4. CPU

5. ALU

6. CU

1. Input Unit:

▪ It performs following functions:

       a. Accepts instructions and data from                         outside world.

       b. It converts instructions and data in                          computer acceptable form.

       c. It supplies the converted instructions and             data to the computer system for

further processing.

▪ Data and instructions enter in the computer in a form that depends upon input

device being used.

▪ All input devices must transform input signals to binary codes which are done by

input interface.

▪ Input interface watch unique physical and electrical characteristics of input

device.

2. Output Unit:

▪ It performs reverse of input unit.

▪ It performs following functions:

a. It accepts the results produced by the computer, which are in coded form.

(can’t understand by us)

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

c. Supplies the results to outside the world.

▪ Results produced in binary form. Output interfaces convert binary code into

human readable form.

3. Storage Unit:

▪ It holds:

a. Data and instructions required for processing.

b. Intermediate results of processing.

c. Final results of processing data before they are released to output unit.

▪ 2 types of Storage Unit:

a. Primary Storage:

o It is also known as Main Memory.

o It stores pieces of programs and data, intermediate results and recently

produced results.

o The CPU can directly access these pieces at fast speed.

o It is volatile.

o It has limited storage space.

o It is made up of semiconductor devices.

▪ Secondary Storage:

o It is also known as Auxiliary Device.

o It is cheaper than Primary storage.

o It is non-volatile memory.

o Magnetic disk, Hard disk is used as secondary storage.