Computer System

Computer is an electronic Machine that can be programmed

To do a wide variety of tasks .

Desktop and laptop are example of personal computer ( PCs)

Example of personal computer

Types of Computers

I.MINI COMPUTER : It is powerful computer that

can support many users at a time

It is a large, high-powerComputer that can perform

Billions of calculations From multiple sources at the

Same time.

iii. Super computer:

It is a machine that can processBillion of instruction in a

Second and is used to solveExtremely complex

Calculations.

Super computer

Characteristics of computer

i. Speed

Computer speed is measured In Megahertz(MHz)Or gigahertz(GHz)

ii. Storage :

A computer has internalStorage (memory)as well as

External . In secondary storage,Large amounts of data & programs

Can be stored for future use.

iii. Calculations/operations

A computer can performArithmetical & logical

Operation.

iv. Accuracy :A computer is highly accurate In doing calculations. It gives

An accurate output resultProvided correct input data is

Fed into in.

v. Reliability :

A computer have very low failure vate.

vi. Versatility :Various tasks can be

Performed on a computer.

vii. Communication : Used to exchange message or data

through Computer Network

viii. Diligence :

A computer can continuouslyWork for hours without

Making any errors.It dose not get tried.

Components of computer

Input devices :

The input or instructions to the computer is given through input devices such as keyboard, mouse, scanner , etc.

Input devices

Example:Mouse :It is a device that allows you to point things on the screen of the monitor, click, and open files & folders.

OUTPUT DEVICES:Output devices are used to show the result of the operation performed by the computer such as monitor, printer

Monitor :This device operates like a TV set and lets the users see how the computer is responding to their commands

Central Processing Unit :

CPU is the most important component of a computer. It is responsible for executing various instructions, performing arithmetic and logic operations and controlling various input/output devices. So CPU is called as “ brain“ of the computer.

i.The first step in this cycle is to fetch instructions from memory.

ii.To decode the instructions and organize the decoded information.

iii.Involves the execution of instructions.

iv.To write-back the results that occurred during execution step.

The CPU undergoes a series of four steps, to complete its cycle of operations.

Three major unit of CPU

i. Storage or memory unitMemory is the area of a computer

where all the data and instructions are stored.

Types of memory

:Primary memory IT IS THE MAIN MEMORY OF THE COMPUTER. IT STORES THE OPERATING SYSTEM PROGRAMS AND DATA CURRENTLY USED BY THE CPU. IT CONSISTS OF ‘ RANDOM ACCESS MEMORY’ ( RAM) & ‘ READ ONLY MEMORY’ (ROM)

RAM : RAM contains storage cells that can be accessed directly for read and Write operations. It is used temporarily store data while the CPU working on it.

There are two types of RAM : dynamic (DRAM) & Static ( SRAM)

SRAM retains the data as long as the power is on SRAM is primarily used for small amounts of memory , called registers, in a computer’s CPU and for fast ‘ cache ‘ memory.DRAM is smaller in the size than SRAM, but is much slower it also stored data for a very short time .Therefore data stored in DRAM needs to be refreshed periodically even when the power is on. Because of its small size, DRAM is generally used for the main memory of the computer

:ROM ROM is unlike RAM . It dose not lose data when power is switched off. Once data is written on a ROM, we cannot rewrite on it. ROMs are used for storing programs that are essential parts of a computer’s operations, such as bootstrap program that starts a computer & loads its operating system that addresses external devices in a personal computer.

E There are three types of ROMs.PROM- Programmable ROM. The information recorded on this cannot be erased.EPROM-Erasable programmable ROM. The information recorded on EPROM can be erased by exposing it to UV light.EEPROM- Electrically erasable programmable ROM. The information recorded on EEPROM can be erased by using electrical signals.

Secondary memory Secondary memory refers to auxiliary storage devices like the hard disk, floppy disk, CD ROM, DVD, etc. these are called the non –volatile memory devices or the permanent storage devices.

Floppy disk

CD ROM

DVD

Hard Disk

Control unit (CU)Control unit manage the operation of the CPU

ARITHMETIC LOGIC UNITIt perform arithmetic and logical operations

Control unit

Arithmetic logic

unit(ALU)

Secondary storage

Memory unit

Input

Output

IPO Cycle

Applications of computer

i. Education institutions •Help teachers prepare assignments•Impart computer – aided learning •Explore and use online resources •Help students make projects•Keep track of grades •Make circulars•Keep and maintain all accounts

Photo of education institutions

Hospitals: •Hospital administration•Recording/maintaining the medical history of the patients•Diagnosis of diseases •Monitoring the condition of patients

Banks:•Opening new accounts & managing the

existing ones•Maintaining & updating customer information •Tracking & recording transactions•Managing online transactions•Storing information about products and services offered by the bank

Designed

By

lumbini