COMPUTER BASICS

Alak Roy

Assistant Professor

Dept. of CSE

Royal Group of InstitutionEmail : alakroy.nerist@gmail.com

CS-107 INTRODUCTION TO COMPUTING

Aug-Dec,2010

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What is 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) from the user, stores and process the given input to generate the output in the form of useful information to the user.

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Data and InformationDATA Data 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.

All computer processing requires data.

INFORMATION meaningful, organized, and useful data is called

information Computers manipulate data to create information.

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Why is a Computer so Powerful?

Perform information processing with amazing speed. Reliable. Accuracy. Ability to store huge amounts of data & information. Ability to communicate with other computers.

Components of Computer Systems

System Unit Keyboard Mouse Monitor / Display Printer

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Devices that comprise a computer system

Printer (output)

Monitor (output)

Speaker (output)

Scanner (input)

Mouse (input)

Keyboard (input)

System unit(processor, memory…)

Storage devices

(CD-RW, Floppy, Hard disk, zip,…)

Basic 2 Parts?

1. Hardware

2. Software

Software Software is a part of the computer you cannot touch.

Definition of Software: Software is a set of instruction & computer programs and

procedures that that help the computer in caring out their processing.

Necessary for proper functioning of computer.

Computer software is divided into two basic types:

1. System software

2. Application software

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System software

The program which are designed to control the different operations of the computer are known as system software.

•Operating System is the base program on a computer is considered system software. • It tells the computer how to work or operate. 

System software Operating system software tells the computer how to perform

the functions of loading, storing and executing an application and how to transfer data.

The operating system also allows you to load other programs that do specialized tasks on to your computer. (ex. Windows XP and Vista)

Microsoft Windows 98 is a widely used graphical operating system. DOS (Disk Operating System) is an older but still widely used operating system that is text-based.

Application Software

The program which are designed to perform a special task for the user are known as application software.

Application Software consists of programs that tell a computer how to produce information.

Some of the more commonly used packages are:

1. Word processing

2. Electronic spreadsheet

3. Database

4. Presentation graphics

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Or The computer and all equipment attached to it are

called hardware.

The hardware is the part of the computer you can touch and see.

Definition of Hardware:A group of electronics physical devices that make up a computer .

Hardware

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1. Input devices.

2. Processing devices or (Central Processing Unit)

3. Output devices.

4. Memory

5. Storage devices.

Hardware Parts

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What does A Computer Do?

Computers can perform 5 general operations, which comprise the information processing cycle.

Inputting Processing Storing Outputting Controlling

Block diagram of Computer

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Magnetic TapeMagnetic Tape Magnetic diskMagnetic disk

Primary MemoryPrimary Memory

Secondary memorySecondary memory

Arithmetic & Logic unitArithmetic & Logic unit

Control UnitControl Unit

Input UnitInput Unit Output UnitOutput Unit Output MediaOutput MediaINPUT MediaINPUT Media

CPU UNIT

MEMORY UNIT

External STORAGE unit

ControlControl

Control instruction to unitsControl instruction to units

Data & Result FlowData & Result Flow

instruction to control unitsinstruction to control units

Input Unit Accepts or read data & program to

computer Convert input information into suitable

binary form acceptable to the computer Supplies converted data & instruction to the

computer system for further processing

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Output Unit

1. It Convert machine readable information into human readable form.

2. Output unit / devices receive the processed data from the CPU and present it to the user in a desired form.

3. Act as an interface between computer and user

4. It supplies the converted result to outside world

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Central processing Unit (CPU)or Processing Devices

considered the “brain” of the computer.contains electronic circuits that cause processing to occur.

Main Functions of CPU: CPU interprets instructions to the computer, CPU execute program,CPU performs the logical and arithmetic processing operations, andCPU Controls operations of all other components such as input/output devices.CPU causes the input and output operations to occur.

CPU Consist of: Arithmetic & Logic Unit (ALU)

Performs arithmetic & logic operations (+,-,*,/,or,not,xor, etc..) Control Unit (CU)

Control & coordinates the activities of all other units (ALU,Memory,i/o) CU gets instruction out of memory unit & decode instructions.

Buses Address Bus Data Bus Control Bus

Clock

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CPU Consist of: Registers (CPU contains special purpose, temporary storage unit)

Program Counter (PC): to keep track of next instruction to be executed. Instruction Register (IR): to hold instruction to be decoded by the control

unit. Memory Address Register (MAR): to hold address of next location in the

memory to be accessed. Memory Buffer Register (MBR): for storing data received from or sent to

CPU. Memory Data Register (MDR): for storing operand & data. Accumulator (ACC): for storing the results produced by arithmetic &

logic unit.

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C

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1. Input Devices Basic input devices :

1. Keyboard.

2. Mouse. Special input devices:

1. Touch Screen

2. MICR (Magnetic Ink Character Reader)

3. Scanner

4. OCR (Optical Character Reader)

5. Joystick

6. Light pen

7. Trackball

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1(a) Keyboard1. most commonly used input device

2. on which data is entered by manually keying in or typing certain keys.

3. A keyboard typically has 101 or 105 keys.

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1(b) Mouse1. pointing device,

2. which is used to control the movement of a mouse pointer on the screen to make selections from the screen.

Mechanical Mouse• A mouse has one to five buttons.• The bottom of the mouse is flat and contains a mechanism that

detects movement of the mouse.

Optical Mouse

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• Special VDU (Visual Display Unit) devices have touch sensitive screens.

• Recognize magnetically charged character

• Uses magnetic ink for writting

• Mainly found on bank cheques

OCR (Optical Character Reader) Scan a particular document by recognizing its individual

characters & converting it into the editable form. OCR, distinguishes the dark area on the document from the

light areas for recognizing the characters.

OMR (Optical Mark Reader) Scan only the box area Helps in obtaining data from marked fields E.g.: Multiple choice question paper.

Bar Code Reader Reads bar codes, which is used to label items in super markets Bar codes are scanned, and later converted into number or

letters using decoder.

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Scanner Used for digitizing images Input device that can electronically capture text and images and

convert them in to Computer readable form. Types of scanner:

1. Hand held scanner

2. Flatbed scanner

3. Drum scanner

Joystick Pointing device Consist of one or more buttons and a sticks, which controls the

movements of the cursors on the screen. Used to move cursor position on a monitor screen

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Light pen Pointing device Used to select a displayed menu item or draw picture on screen Consist of photocell & an optical system placed in a

small tube Detects screen location & sends corresponding signal to

CPU

Trackball pointing devices Looks and works like mouse

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3. Output DevicesMost Commonly used are:

Monitor Printer

Others are: Plotters Projectors Voice output systems

3(a): Monitor

is the display screen, similar to a television screen. VDU (Visual Display Unit) produces a soft copy of your output.

Monitor Types based on Technology:1. CRT : Cathode Ray Tube

2. LCD : Liquid Crystal Display

3. TFT : Thin Film Transistor

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Self Study (in detail)

Types of Monitor (depending upon number of pixels, resolution):

1. CGA : Colour Graphics Adapter. (310X320) (Text & graphics)

2. MDA : Monochrome Display Adapter (Text) 3. HGA : Hercules Graphics Adapter (310X320) (Text & Mono graphics)

4. EGA : Enhanced Graphics Adapter (640x350) (Text & Enhanced graphics)

5. VGA : Video Graphics Adapter (640x480) (Text & video graphics)

6. SVGA : Super VGA (1600x1280) (Text & video graphics)

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3(b): Printer Is a computer hardware that produces a hard copy of

information processed by a computer system.

Types of Printers: Impact Printers

Dot matrix printers Daisy wheels printers Drum printers

Non Impact Printers Ink-jet printers : Laser printers 32

Self Study

Impact Printers Printer in which there exist a mechanical contact between

print head and paper. Contains individual print head (resembles a hammer) for each

character, print head responsible for transferring ink to the paper, Print Head of a character strikes ink ribbon, ink ribbon in turn

strikes paper, leaving an impression of that character on the paper.

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Non Impact Printers Printer in which there exist no mechanical contact between

print head and paper. Printer spray ink on the paper with the help of nozzle. Do not produce noise, faster then impact printer

Dot Matrix Printer Print character using dots Speed measured in character /sec Quite noise Cheap

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Inkjet printer: Non impact printer print character by spraying small drops of ink onto

the paper. Not very noise Speed measured in character /sec

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Laser Printer Print character completely Speed measured in pages Not very noise expensive

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4. Memory & Storage Devices

Units of Storage– 1 bit– 8 bits = 1 byte– 1kbyte = 1024 bytes– 1Mbyte = 1024 Kbytes = 1048576 bytes– 1GB (Giga byte) = 1024 Mbytes– 1TB (Tera byte) = 1024 GB

main types:1. Data Storage (Secondary / Auxiliary memory)2. Main Memory (Primary memory)3. Internal process memory (Cache Memory & Registers)

Memory Representatio

n

012....N

Cost, speed,

capacity

4(a): Memory Memory is a work area within the computer where CPU used to

stores data, instructions & information (bits and bytes) before, during & after the processing by ALU.

Temporary storage medium that holds the data only for a short period of time.

Also known as Main memory or Primary Memory or Internal memory

2 types of Primary Memory: RAM ROM

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RAM - Random Access Memory Volatile

Temporary memory is the main memory of the computer. information stored in RAM is lost when the computer is

turned off. It consists of electronic components that store data

including numbers, letters of the alphabet, graphics and sound. As it is possible to randomly use any location of this memory,

therefore, this memory is known as “Random Access Memory”.

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RAMDynamic RAM

1. Information stored in DRAM has to be refreshed after every few milliseconds otherwise it is erased.

2. DRAM has higher storage capacity.

3. It provides lesser speed to computer.

4. It is cheaper.

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Static RAM1. Information stored in SRAM

need not to be refreshed, but it remains stable as long as power supply is provided.

2. SRAM has lesser storage capacity.

3. It provides more speed to computer.

4. It is costlier.

ASRAM: Asynchronous SRAM•Perform operation without use of system clock

SDRAM: Synchronous DRAM•Perform operation with use of system clock

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ROM - Read Only MemoryNon-volatile

Won’t disappear when power is off It is permanent memory.

ROM is memory that is etched on a chip that has start-up directions for your computer.

Most important program of ROM is BIOS (Basic Input Output System) that activates the hardware.

Types of ROM1. Mask ROM

Information is stored at the time of its manufacturing. It cannot be altered or erased later on.

2. PROM (Programmable Read Only Memory) Information is stored by programmer after its manufacturing. It cannot be altered or erased later on.

3. EPROM (Erasable Programmable Read Only Memory) Information is stored by programmer after its manufacturing. but its information can erased on by ultra violet light and it can be

reprogrammed.

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4. EEROM (Electrically Erasable Programmable Read Only Memory)

Information is stored by programmer after its manufacturing.. but its information can be erased by using high voltage

current.

5. EAPROM (Electrically Alterable Programmable Read Only Memory)

Information is stored by programmer after its manufacturing. information can be altered later

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4(b): Data StorageSecondary Memory or Auxiliary storage devices used to store data when they are not being used in memory. most common types of auxiliary storage used:

floppy disks, hard disks and CD-ROM drives.

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DisksFloppy Disk Holds 1.44 Megabytes

1,440,000 Bytes

Feels hard Floppy part inside cover

Almost obsoleteA 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.

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Floppy Disk contd..

The disk’s storage locations are divided into pie-shaped sections called sectors.

A sectors is capable of holding 512 bytes of data. A typical floppy stores data on both sides and has 80

tracks on each side with 18 sectors per track.

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4(b) Hard Disks

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.

The hard disk platters spin at a high rate of speed, typically 5400 to 7200 revolutions per minute (RPM).

Storage capacities of hard disks for personal computers range from 120 GB to 1024GB (one billion bytes are called a gigabyte).

•Main disk for most computers•Holds Windows, software, and most data•Usually don’t see it because it’s inside computer.

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4(c) Compact Discs (CD) also called an optical disc, is a flat round, portable storage medium that is usually

4.75 inch in diameter. A CD-ROM (read only memory), is a compact disc that

used the same laser technology as audio CDs for recording music. In addition it can contain other types of data such as text, graphics, and video.

The capacity of a CD-ROM is 650 MB of data.

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DVD Replacing CD-ROM Holds much larger amount of

information (such as movie) 4.7GB

4(c) Cache Memory Small, fast, expensive memory that

stores the copies of data that need to be accessed frequently from the main memory.

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Main Memory

Processor

Cache Memory

Two Types of Cache Memory:Primary Cache

known as “L1 Cache” or “Internal cache” , located inside the CPU.

Secondary Cache known as “L2 Cache” or “External cache” , located on

the motherboard of a computer.

What is virtual memory? Virtual memory is hardware

technique where the system appears to have more memory that it actually does.

This is done by time-sharing, the physical memory and storage parts of the memory one disk when they are not actively being used.