Computer System

Understanding Computer System


Understanding Computer System

What is Computer System ?

A computer system is a set of integrated devices which takes input, process it and give output. Also it store data and information.computer system allows users to input, manipulate and store data. Computer systems include a CPU, monitor, keyboard, mouse and other optional components.

What is Computer ?

Definition : Computer is an electronic device that takes data as an input  and processes it under the control of a set of instructions (called program) and then produces a result (output), and all the set is called as computer system.

Computer System

All general-purpose computers require the following hardware components :

Memory  :  It is used to store data and programs.It may be temporary or permanent
e.g RAM,ROM

Mass storage device  :  Allows a computer to store large amount of data permanently.
e.g Hard Disk.

Input device  :  Any device that sends data to a computer is called input device.
e.g keyboard and mouse

Output device  :  Any device  that outputs information or  data from a computer to another device is called output device.
e.g display screen, printer

central processing unit (CPU) :  This is also called as heart of the computer, CPU is responsible for  executes instructions. It receives data input, executes instructions, and processes information and then generate appropriate result.Sometimes referred to simply as the central processor, but more commonly called processor.


Block Diagram of Computer System

The Basic components of computer system are given below :

computer system

a) Input Unit
b) Output Unit
c) CPU (Central Processing Unit)
i) Control Unit ( C U)
ii) Arithmetic logic Unit ( A L U)
iii) Main Memory unit ( M M U)
d) Storage Unit

a) Input Unit :

Computers need to receive data and instruction in order to process the task. Therefore we need to input the data and instructions into the computers. Keyboard and mouse is the one of the most commonly used input device.

b) Output Unit :

The output unit of a computer receive output from CPU (Central Processing Unit). Example of Output Unit is Printers,Monitor, etc. Other commonly used output devices are floppy disk drive, hard disk drive, and magnetic tape drive.

c) CPU (Central Processing Unit) :

This is main Part of computer system, Is also known as processor and consist of three units which is as follow ,

i) Control Unit ( C U)
ii) Arithmetic logic Unit ( A L U)
iii) Main Memory unit ( M M U)

i) Control Unit ( C U) : It controls all other units in the computer. The control unit instructs the input unit, where to store the data after receiving it from the user.
A control unit (CU) handles all processor control signals, control unit directs the entire computer system its also communicate with both the arithmetic logic unit (ALU) and main memory.
The control Unit or CU Controls or coordinates all activities performed in a computer system.

ii) Arithmetic logic Unit ( A L U)  : All calculations are performed in the Arithmetic Logic Unit (ALU) of the computer. It also does comparison and takes decision.
Arithmetic operation comprises of (Addition, subtraction, division, multiplication) and the logical unit carries out the operation such (AND, OR, Equal, less than, greater then).
Data is transferred to ALU from storage unit when required. Whenever calculations are required, the control unit transfers the data from storage unit to ALU once the computations are done, the results are transferred to the storage unit by the control unit and then it is send to the output unit for displaying results.

iii) Main Memory unit ( M M U) : The main memory unit is used for storage of the copy of the main software program that controls the general operation of the computer.
and temporary storage of a copy of application program instruction, to be received by CPU for interpretation and processing or execution.

d) Storage Unit :

Storage unit is the unit which gives space to store data or instruction of processed data.
It stores information or instruction
It stores Results
It stores consequence of prepared data

There are mainly two types of storage Unit
i) Primary Storage
ii) Secondary Storage

i) Primary Storage : They are also called as Main memory or in other words as RAM (Random Access Memory).
The primary Storage cannot store huge amount of data, and the data store in this memory is temporary (The data is lost when there is power failure), it is also called as temporary memory, they are very expensive.
The other example of primary Storage is L1 Cache of Processor ,RAM

ii) Secondary Storage : Secondary storage are also called as permanent storage unit as when the data store in this memory are stored permanently .The data remains in this memory even when there is a power failure or shutdown, they are much more cheaper then primary memory.
The Example of Secondary Storage are Hard disk and Zip drives


Computers also classified by size and power, which is as follow.

Personal computer  : It is small in size, single-user computer, based on a microprocessor. A personal computer has a keyboard for entering data, a monitor for displaying information, and a storage device for saving data.

Workstation  :  It is powerful compare to personal computer, single-user computer. It is same as a personal computer, but it has a more powerful microprocessor and a higher-quality monitor.

Minicomputer  :  It is multi-user computer which is capable of supporting from 10 to 100 of users simultaneously.

Mainframe  :  It is powerful multi-user computer which is capable of supporting 100 to 1000 or more of users simultaneously.

Supercomputer  :  An extremely fast computer that can perform hundreds of millions of instructions per second, it is basically used by scientist or researchers.



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