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What is a PC?Components of a PCMain UnitCPUMemoryKeyboardPeripherals

What is a Computer?What is a Computer?

A computer is an electronic device, operating under the control of instructions (software) stored in its own memory unit, that can accept data (input), manipulate data (process), and produce information (output) from the processing. Generally, the term is used to describe a collection of devices that function together as a system

Computer systems have four parts– Hardware– Software– Data– User

What Does A Computer Do?What Does A Computer Do?

Computers can perform four general operations, which comprise the information processing cycle.

Input Process Output Storage

Computers use the same basic hardwareHardware categorized into four types

Four partsFour parts

– Processing Devices– Memory Devices– Input and Output Devices– Storage Devices

What Are The Primary What Are The Primary Components Of A Computer ?Components Of A Computer ?

Input devices.Central Processing UnitMemory.Output devices.Storage devices.

Structure of a Computer System Structure of a Computer System (Information Processing Cycle)(Information Processing Cycle)

Output

Auxiliary Storage

CPU

RAM Input

Data and InformationData and Information

All computer processing requires data, which is a collection of raw facts, figures and symbols, such as numbers, words, images, video and sound, given to the computer during the input phase.

Computers manipulate data to create information. Information is data that is organized, meaningful, and useful.

During the output Phase, the information that has been created is put into some form, such as a printed report.

The information can also be put in computer storage for future use.

Input DevicesInput Devices

Keyboard Mouse or Trackball Joystick Touch Screen Light Pen Image Scanner Digital Camera Voice Input

KEYBOARDKEYBOARD

The Keyboard is an input device.Older Keyboards were 84-keysCommon keyboards are 102-keysMultimedia supported keyboards 109-keys

Keyboard Normally consists of Keyboard Normally consists of Four main parts.Four main parts.

1.Typewriter or Alphanumeric Keys(because it has the alphabet and numbers.)

2. Arrow keys or Cursor keys (pointing up, down, left and right move the cursor)

3. Numeric keypad or Num keypad(Numbers 0 to 9, decimal point, num lock)

4. Function Keys F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11 and F12.

Mouse Mouse

A mouse is also an input device. A mouse usually has two or three finer buttons that you

can press: One on the left, one on the right and (sometimes) one on the centre

In Windows applications, clicking the left mouse button will make your computer do something, like opening a folder or starting a program. Often you will need a double click. Clicking on the right mouse button will provide you with information and/or a menu of operations that you can choose from.

(CPU) Central Processing Unit(CPU) Central Processing Unit

The central processing unit (CPU) contains electronic circuits that cause processing to occur. The CPU interprets instructions to the computer, performs the logical and arithmetic processing operations, and causes the input and output operations to occur. It is considered the “brain” of the computer.

Structure of CPUStructure of CPU

Control Unit

Memory (Registers)

Arithmetic and Logic Unit

Output DevicesOutput Devices

MonitorSpeakerPrinterPlotter

MonitorsMonitors

Cathode Ray Tube (CRT)– Most common type of monitor– Electrons fired from the back– Electrons excite phosphor to glow– Phosphor is arranged in dots called pixels– Dot mask ensures proper pixel is lit

CRT drawbacks– Very large – Very heavy– Use a lot of electricity

MonitorsMonitors

Liquid Crystal Display (LCD)– Commonly found on laptops– Desktop versions exist– Solve the problems of CRT– Fluorescent lights provide illumination

Storage DevicesStorage Devices

Volatile Memory (RAM)Non-Volatile MemoryROM

Hard Disks

Floppy Disks

Compact Discs – CD and DVD drives

Volatile MemoryVolatile Memory

Memory also called Random Access Memory or RAM (temporary memory) is the main memory of the computer. It consists of electronic components that store data including numbers, letters of the alphabet, graphics and sound. Any information stored in RAM is lost when the computer is turned off.

Non-Volatile MemoryNon-Volatile Memory

Read Only Memory or ROM is memory that is etched on a chip that has start-up directions for your computer. It is permanent memory

The contents of ROM remain when power is switched off.

Floppy DisksFloppy Disks

Auxiliary storage devices are used for permanent storage of data

A floppy disk is a portable, inexpensive storage medium that consists of a thin, circular, flexible plastic disk with a magnetic coating enclosed in a square-shaped plastic shell

Hard DisksHard Disks

Another form of auxiliary storage is a hard disk. A hard disk consists of one or more rigid metal plates coated with a metal oxide material that allows data to be magnetically recorded on the surface of the platters

Compact DiscsCompact Discs

A compact disk (CD), also called an optical disc, is a flat round, portable storage medium that is usually 4.75 inch in diameter.

CD-ROM (read only memory), CD-RW – (rewritable) DVD-ROM DVD+RW

Hardware vs. SoftwareHardware vs. Software

Hardware - the physical parts that make up the computere.g. CPU, memory, disks, CD-ROM drives, printer.

Software - computer programs and applications.– Operating system, word processor, games, etc

SoftwareSoftware

A computer program or software tells it exactly what to do.

A computer program is a set of instructions to the computer.

Computer software is the key to productive use of computers. Software can be categorized into two types:

System software Application software.

Application SoftwareApplication Software

Application Software consists of programs that tell a computer how to produce information. Some of the more commonly used packages are:

Word processing Electronic spreadsheet Database Presentation graphics

System SoftwareSystem Software

The most important system software is the operating system.

Examples of operating systems:Windows, DOS, Apple, UNIX

Purpose of an Operating System?Purpose of an Operating System?

An OS is a computer program that:Provides the interface between you and

your computerControls the hardware of the computer.Run your computer applications or

programsCommunicate with your network

Classification of Computers or Classification of Computers or Types of ComputerTypes of Computer

Computers can be classified into three ways:

According to FunctionAccording to Size and CapacityAccording to Purpose

According to FunctionAccording to Function

According to function computers can be classified into three types, namely:

Analogue Computers Digital Computers Hybrid Computers

Analogue ComputersAnalogue Computers

Usually all the measuring devices are called Analogue computers.

An analogue computing devices can measure only the continuously variable quantities, such as Temperature, Pressure, Voltage, sound etc.

Digital ComputersDigital Computers

Digital computers are high speed, programmable electronic devices that performs mathematical calculations, compare values and store the results. They recognize data by counting discrete signals. Representing either a high (on) or low (off) voltage state of electricity.

Working on Binary values (0) and (1)

Hybrid ComputersHybrid Computers

In special situations digital and analogue computers have been combined to create hybrid computers. The capacity of hybrid computers is most significant where the digital processing of data collected in Analogue form is desirable.

Petrol pump machines and speedometers are some example of hybrid computers.

According to Size and CapacityAccording to Size and Capacity

Lap Top / Notebook, Palm TopMicro Computers Mini Computers Macro Computers (Main Frames)Super Computers

Lap Top / Notebook, Palm TopLap Top / Notebook, Palm Top

These are the smallest computers in size

Look like office briefcase geometry box

They are termed as portable computers

These are very popular in use because of small size and less weight.

Tablet computersTablet computers

– Newest development in portable computers

– Input is through a pen

– Run specialized versions of office products

Micro Computers Micro Computers

Micro computers are small machines These are low in priceIt is cheaper, so there is no difficulty to

maintainSmall business application can run on itHome computed work can be performedIt is also called PC personal computer

Computers at home– Many homes have multiple computers– Most American homes have Internet– Computers are used for

Business Entertainment Communication Education

Mini ComputersMini Computers

– Called midrange computers– Power between mainframe and desktop– Handle hundreds of users– Used in smaller organizations– Very popular for time sharing system– These computers are used in laboratories for all

types of engineering and scientific work.

Macro Computers (Main Frames)Macro Computers (Main Frames)

They are large in size Also called main frame computers Used for networking as a main

server Main frame computers supports

thousands of users Used in world wide Airline

Reservation system They are used for a high amount of

data processing and used as centralized data machine (e.g. Citibank credit card machine)

Super Computer

These are very large in size Use for complex scientific

calculations Its capabilities are much more than

main frames Very costly Super computer supports small no of

users These are used in Nuclear physics,

weather forecast and satellite controlling

Supercomputers– The most powerful computers made– Handle large and complex calculations– Process trillions of operations per second– Found in research organizations

According to PurposeAccording to Purpose

General Purpose Special Purpose

General Purpose computersGeneral Purpose computers

These computers are designed to perform various tasks and can be used for different calculations of data, for example personal computers can perform different tasks of work. It can compute data it can solve different problems, it can play music, videos etc…

Special Purpose computersSpecial Purpose computers

These types of computers can do only predefined work and is useless for any other kind of work. For example Visa card Machine can only insert Visa cards and can verify them. It cannot calculate any data.

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