FUNCTIONAL UNITS OF A COMPUTER

A computer consist of five functionally independent main components they are:

• Input Unit
• Memory Unit
• Arithmetic & Logic Unit
• Output Unit
• Control Unit

The input unit accept the coded information from human operations from electrical devices such as keyboard or from other computer over digitized communication lines the information receive or immediately used by the arithmetic & logic circuits to perform the desired operations the process steps are determined by a program stored in the memory finally the results are sent back to the outside world through the output unit all of these actions are controlled by the control unit

The following diagram shows the connections among the functional units

Input Unit

The input unit accepts the coded information through the input devices which records the data. The most commonly using input device is keyboard whenever a key is pressed, the corresponding letter or digit is automatically translated into its corresponding binary or to the processor many other kinds of input devices are available including mouse, trackball, joystick etc. These are used as graphical input devices mirophones can be used to give the audio input.

Memory Unit

The functions of memory unit is to store the program and data depending upon the size and storage capacity memory is classified into two types such as 

•  Primary Memory
• Secondary Memory

Primary Memory

It is the first memory that operates at electronic speed program must be stored in the memory while they are being executed. The memory contains large number of semi conductors, Storage cells, each cell is capable of storing one bit of information

To access word of data easily from memory, distinct address are associated with each word addresses are numbers that identifies the successive location by using these addresses, we can easily retrive the data which is already store

The primary memory is classified into two types such as:

• Random Access Memory (RAM)
• Read Only Memory(ROM)

Secondary Memory

Since primary memory is expresive and storage capacity is less hence secondary memory is used for these purpose which can store large amount of data permanently and can be accessed easily as and when required by the user

Arithmetic &  Logic Unit

The arithmetic & logic unit allows the user perform arithmetic calculations and logical operations must computer operations are executed in ALU after the processor the operands are stored in right speed elements

Memory Access Time

The time required to access one word from the memory is called memory accesss type.

Output Unit

The task of output unit is to send processed information or results to the outside world. The most familier example for such output devices are monitors, printers, speakers, projectors etc..

Control Unit

The above four units stores and process the information perform I/O operations. Data transfer between the processor and the memory are controlled by control unit through timming signals.

• The computer accepts the information in the form of programs and data through an input unit and stores it in memory
• Information stored in the memory is fetched under program control into an arthematic & logic unit where it is processed
• Processed information leaves the computer through the output unit
• All activities inside the machine are directed by the control unit

Note : A bit of instructions that perform a specific task is called program. The computers are completely controlled by the stored programs.