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Monday, October 31, 2011

Fundamentals of Data Processing - For Test, Interview and Viva

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Q.1 Define Data and Information. Differentiate between Data and Information.

DATA

Data is the collection of raw facts and figures. It is without any proper meaning.
Data may be collection of words, numbers, graphics or sounds.

Examples of Data

1) When students get admission in a college. They fill admission form. This form contains raw facts (data of student) like name, father’s name, address of student etc.
2) During census, data of all citizens is collected.

INFORMATION

Processed data is called information. When raw facts and figures are arranged in some order then they become information. Information has proper meanings. Information is useful in decision-making. Actually we process data to convert it into information.

Exapmle of Information:

1) Stored data of students can be used to print address labels of students.
2) Census data is used to get report/information about total population of a country and literacy rate etc.

Q.2 Describe types of Data.

There are followimg types of Data.
1) NUMERIC DATA:Numeric data consists of 0 to 9 digits, + and – sign and decimal point etc.
For example, 10, 78, 90.50, -56 etc
2) ALPHABETIC DATA
It consists of all alphabetic letters A to Z, a to z and blank space etc. For example, Pakistan, Ahmad, Abdul Rahim, GCC , RYK, Ahmad etc.
3) ALPHANUMERIC DATA
It consists of alphabet letters, digits and special characters like #, $, % etc.
For example, House Number 10-A, 14-August-1947, F-16 etc.
4) GRAPHIC DATA
Graphic data or image data consists of charts, graphs and images etc. For example a collection of maps of countries, a collection of family pictures etc.
5) AUDIO DATA
Audio data consists of sounds and voices. For example audio naat, radio program, radio news
VIDEO DATA:Video data consists of moving pictures. For example movie, TV dram, TV news etc.
6) MIXED DATA:Mixed data consists of combined data of two or more types. For example, TV drama consists of audio as well as video data.

DIFFERENCE BETWEEN DATA AND INFORMATION


DATA
INFORMATION
1
Data is collection of raw facts and figures.
Information is processed data.
2
Data is not arranged.
Information is arranged.
3
Data is unorganized.
Information is organized.
4
Data is not so meaningful.
Information is Meaningful.
5
Data is input.
Information is out put.

Q.3 Define data processing and explain types of data processing.

DATA PROCESSING

Data processing is the sequence of operations performed on data to convert it into useful information. These operations may be arithmetic, statistical or logical operations. We can arrange or classify data.

TYPES OF DATA PROCESSING (OR) LEVELS OF DATA PROCESSING)

There are three types of data processing.

1) Manual data processing

In manual data processing data is processed manually. No machine or tool is used.
All the calculations on data are performed manually. This is a slow method and errors may occur..

2)Mechanical Data Processing

In mechanical data processing data is processed with calculators or other mechanical devices. This method is faster and more accurate than manual data processing.

3) Electronic data processing

It is the latest method of data processing. Data is processed with computer

Q.4 Describe how data is transformed into information. OR Explain Data Processing Cycle.

DATA PROCESSING CYCLE

After collecting data, it is processed to convert into information. The data is processed again and again until accurate result is achieved. This is called data processing cycle. Data processing cycle involves following three basic activities: 1) Input 2)Processing 3) Output

Q.5 What is the need of Data processing in business?

NEED OF DATA PROCESSING IN BUSINESS
There is no more business without information. To improve the business there is a need to improve data processing and information system. The need of data processing in business is clear. Following are the reasons:
RECORD KEEPING , ACCESSING RECORDS , COMMUNICATION, COST, SPEED, ACCURACY, REPORTS
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Saturday, October 29, 2011

Computer Networks - Test Interview Viva Voce

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Q1. Define Network with example. Give importance of computer network.



 

COMPUTER NETWORK
A computer network is a set of two or more computers connected together to share information and other resources. The computers in a network can share:
  1. Data, information  and Files
  2. Resources (printers, Cd-Rom Drives, DVD- Rom Drives, CD- Writers, hard disk, modems)
  3. Programs / software

EXAMPLES OF COMPUTER NETWORK


  1. Computer network can be used in an organization's office. Different employees and managers in the office and organization can share common information.

  2. Internet, is also an example of a computer network. Internet is a network of millions of computers connected through phone lines. People can share information, files and talk with one another through internet.

  3. Internet cafe also uses computer network for internet sharing on all computers.

  4. A Computer laboratory in a school or college may use local area network for sharing data and other reources like printers, Cd-Rom drives or hard disks etc.

ADVANTAGES OF COMPUTER NETWORKS

Following are some important advantages of computer networks:

  1. Information Sharing
    Data and information can be shared by many users.

    Hardware Sharing

  2. Hardware Resources like printer, scanner, CD-ROM drive and hard disk can also be shared.
  3. Money Saving
    We can save a lot of money by using the same software and hardware in a network.
  4. Easy and Fast Communication
    We can send and receive emails and share files with other people in the company or in any part of the world through network or internet.

Q2. Explain different types of computer networks: (LAN,WAN,MAN).

Main types of computer networks are: 1. LAN - Local-Area Network 2. WAN - Wide-Area Network 3. MAN - Metropolitan-Area Network

LAN (Local Area Network)

LAN stands for Local Area Network. It covers a small area. Most LANs are used to connect computers in a single building or group of buildings. Examples: Following are two examples of LAN: • LAN is used in a computer lab to connect computers. The students can share software, files and data in the lab. • In Internet cafe, many computers can be connected through LAN. These computers can share single connection of Internet.

2)WAN (Wide Area Network)

WAN stands for wide area network. It covers a large area. WAN connects computers in different cities, countries and continents. Computers in WAN are often connected through telephone lines. The largest WAN is the Internet. Examples of WAN • In air ticketing system like PIA, many offices can be joined together using WAN. A person can get a ticket from any office in the country. • A bank with many branches in different cities can connect its branches through WAN. The customer can use his account from any branch.



3)MAN (Metropolitan-Area Network)

A metropolitan area network (MAN) is a network that covers an area of the size of a city. Example: Mobile phones systems often use MAN.

Q3. Differentiate between LAN and WAN.

The differences between LAN and WAN is as follows:

LAN

WAN

1.

LAN is used to connect computers at one place.

WAN is used to connect computers anywhere in the world.
2.

LAN covers limited area.


WAN can cover more area.

3.

Data transfer speed is very fast in LAN.


Data transfer speed is slow in WAN.

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Wednesday, October 5, 2011

Computer Internet Test Interview Viva Voce

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Q.1 What is internet?

            Internet is the network of networks around the world. It is made up of thousands of smaller networksInternet provides following main facilities:  ·  E- mail                    ·   Chat           ·Searching  jobs    ·       Advertising for business            ·E-commerce     ·Searching information

Q.2 Define :WWW, ISP, WEB PAGE, WEB SITE, WEB SERVER, WEB BROWSER

WWW stands for World Wide Web. It is also called web. It is the collection of all connected web documents stored on different web servers. WWW has many advantages:
· finding a job    ·      searching information ·          e-commerce · education
· advertisement for business   ·         weather forecast  ·     entertainment
ISP stands for internet service provider. It is a company that provides internet connections to users. For example WOL net, PAK net, CYBER net etc. are ISPs.
WEB PAGE:      A document created by HTML and found on web is a web page. A web page contains information in the form of text, pictures, audio and video clips.
WEB SITE:       A collection of related and interlinked web pages is called a web site. A web site may have many pages. Each web site has a unique address called URL. For example URL of Baha-ud-din Zakaria University is www.bzu.edu.pk.
WEB SERVER:Web documents are stored on special and powerful computers called WEB SERVERS. They provide requested information in the form of web page.
WEB BROWSER
            A browser is software that is used to view web pages on internet. Many web browsers are available. But Internet explorer and Netscape navigator are the most popular. Q.3 Write notes on the following:
            INTERNET PROTOCOL, URL, DOMAIN NAME, E-MAIL, E-MAIL ADDRESS
INTERNET PROTOCOL
Internet protocol is the set of rules and procedures used for communication on internet. Commonly used protocols are as following:
·                TCP/IP  It stands for Transmission Control Protocol/ Internet Protocol. It is used to exchange information between web servers and browsers.
·  FTP stands for file transfer protocol. It is used to transfer files on internet easily and quickly.
·                HTTP  It stands for Hyper Text Transfer Protocol. It is used to exchange web pages between web servers and browsers
URL
It stands for uniform resource locator. It is the web address of a web page or a file on internet. For example:
http://www.bzu.edu.pk
DOMAIN NAME
Domain name is a unique name given to a website. This name is linked to a web server where the website is stored. Internet users access your website using your domain name.
A domain name has two or more parts separated by dots, for example:
www.savings.gov.pk
Domain names consist of a top-level domain [TLD](such as .com, .org, and .net) .
E-MAIL:            E-mail stands for electronic mail. Email is an electronic message sent or received through internet. We send our textual messages by email from country to country.

E-MAIL ADDRESS

            E-mail address is a string that identifies a user so that the user can receive Internet e-mail. E-mail address is unique for every user. General format of an email address is as following:
User ID@Email service provider , for example,
m8@wol.net.pk,mahmoodalam786@yahoo.com ,mahmoodalam786@hotmail.com,
Q.4 Write notes on the following:
            FTP, BANDWIDTH, IP ADDRESS, HTML

FTP

            FTP stands for file transfer protocol. It is used to transfer files on internet easily and quickly
BANDWIDTH
            The data transfer capacity, or speed of transmission, of a digital communications system is called BANDWIDTH.
IP ADDRESS
It is a short for Internet Protocol address. This address is a unique string of numbers that identifies a computer connected to Internet
HTML
It stands for HYPERTEXT MARKUP LANGUAGE. It is the language to create and format web pages.
Q.5 What is a search engine, how you can search information on internet?
SEARCH ENGINE
            Internet contains very large amount of information. So it becomes difficult to search some information on internet. To find required information easily and quickly, Search Engine is provided by many websites. Following is a list of popular search engines:
1.         GOOGLE
Google is the most popular search engine. Its address is www.google.com.
2.         YAHOO
It is also a popular search engine. Its address is www.yahoo.com.
3.         ALTAVISTA
Its web address is www.altavista.com.
Q.6 What are ISP EMAIL ACCOUNT (POP3) AND FREE WEB SERVER
EMAIL ACCOUNT? OR Explain different types of email accounts.
There two main types of email accounts:
1) ISP email account   or POP3 email account
ISP or POP3 email account is provided by an ISP. It is generally requires email software like MS outlook express.
2) Web-based Email Account
            On the other hand, there are also many organizations on internet that provide free web based email accounts. These are also called free web server email accounts, for example www.yahoo.com, www.hotmail.com, www.gmail.com
Q.7 What is the difference between ISP MAIL ACCOUNT AND FREE WEB SERVER EMAIL ACCOUNT?
Sr.No.
Web based(free)
Pop3 (ISP)
1
It is provided by companies like yahoo and Hotmail
It is provided by different ISPs like Paknet, Wolnet etc
2
It is totally free
It is not freely available by ISP
Q.8 What are the services provided by internet?
SERVICES PROVIDED BY INTERNET     1.        THE WORLD WIDE WEB    2.    E-MAIL   3.       EMAIL DISCUSSION GROUPS  4.     NEWSGROUPS    5.      ECOMMERCE  6.           FTP    7.           chat
Q.9 What are the advantages and disadvantages of internet?
ADVANTAGES OF INTERNET
Following are the main advantages of internet:
1.   THE WORLD WIDE WEB
This is also called web or www or 3w. The collection of all web pages in all web sites on internet is called www. These web pages provide us information.
2.   E-MAIL:E-mail stands for electronic mail. It is the most popular, cheap, easy and fastest mailing service. We can send and receive messages on internet with in seconds.
3.   NEWSGROUPS:Newsgroups are discussion groups on internet. They are used for free exchange of information.
4.   MAILING LISTS:Mailing lists provide information to the users on the selected topics through email. Mailing lists are maintained by different companies.
5.   ONLINE BANKING
Several banks are online now. So we can manage our bank accounts on internet. Due to online banking, money is transferred from one city or country to another within seconds or minutes.
DISADVANTAGES OF INTERNET
  1. HACKING
Hackers access the important information and programs and may destroy it. Hackers try to get password of internet users and then access important information.
  1. COMPUTER VIRUS
Computer virus is a program developed for some destructive purpose. Computer virus can destroy your data or software. Virus enters into your computer by internet, floppy disc, CD or USB flash memory drive. Antivirus software like Norton Antivirus and  Mcafee  Antivirus are used to find and remove virus.
  1. WASTAGE OF TIME
There are so many interesting facilities on internet. So people use internet for several hours. In this way valuable time is wasted.
Q.10 What is a web browser?
Web browser is software that is used to access information available on internet. It is used to view web pages. The most popular web browsers are Microsoft internet explorer and Firefox
Q.11 Write down notes on the following:   1) Downloading 2) Uploading
Downloading is to receive data from a remote system, such as a website, FTP server, or other similar systems. We can download data in the form of files from internet. Uploading means to  send data from our computer to a remote system such as web site on internet.
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Tuesday, October 4, 2011

Computer Software VIVA

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Q1. Define software. Explain different types of software.


Software is a set of instructions that tell a computer what to do. Examples of software are: MS Word, MS EXCEL, MS POWER POINT, WinZip, Norton Anti Virus, MSN Messenger, MS Windows, DOS, Unix

Q2. Explain different types of software.






The main types of software are system software and application software.
1. System Software
System software is a set of programs to implement certain functions in a computer system. It controls the operations and components of a computer system.

Examples of system software are as follows:

•   Operating Systems:Operating system is a software to control overall operations and components of a computer system. e.g., Windows, Unix, Linux and Dos etc.

•   Utility Programs:Utility program is used to solve a particular problem of software or hardware, for example, Antivirus program, disk scanner and File Viewer etc.

•   Device Drivers:device drier is a software that permits a computer system to communicate with a device. e.g., device driver software for a modem.

2. Application Software

Application software is a program needed to perform various applications on the computer by the user. It helps a computer user to solve specific problems.
Examples of application software are as follows:
i. Word Processing
Word processing software is used to produce letters, applications and other documents, for example MS Word.
ii. Spreadsheets
Spreadsheet program is used for calculations for example MS Excel.
iii. Databases
Database software is used to record data of an organization on computer. MS Access and Oracle are examples of database software.
iv. Graphics
Graphics software is used to produce advertisements, posters etc. for example CorelDraw and Photoshop.
v. Communication
Communications software is used to communicate with different people using Internet, e.g., MSN Messenger, yahoo messenger and Internet Explorer.

Q3. Differentiate between system software and application software

Difference between System & Application Software
System Software

Application Software

1. It is a set of programs to control computer operations and components
1. It is set of programs used to solve particular problems of user.

2.  It is general-purpose software.

2. It is specific purpose software.

4. Examples are: Windows, Dos, Unix, Linux, Norton Antivirus etc.
4. Examples are: MS Word, MS Excel, MS Power point etc.







Q4. What is an Operating System?

Operating System
An operating system is a set of programs that manages all computer components and operations. Without Operating System, a computer cannot do anything. Operating system acts as an interface between a user and computer hardware. Some popular operating systems are DOS, windows, Unix

Q5. Explain Functions of operating system

Functions of Operating System
1. Process Management    2.    Main Memory Management  3.            Secondary Storage Management
4.                  I/O System management    6. File Management     7.      Protection System  8.         Networking

Q6. What is a User Interface? Explain different types of user interface

User Interface is the set of items on screen to interact with the computer. A user interacts and uses computer with the help of these items. For example, Windows Desktop is an example of user interface. Similarly Dos Prompt is also an example of user interface.
There are two main types of user interface:
1)                   Graphical User Interface
Graphical user interface or GUI provides different graphical items like windows, menus, tool bars and icons etc. All versions of Windows, Macintosh, OS/2 and some versions of Unix and Linux provide GUI.
Advantages of GUI:              a) Easy to learn   b) Easy to use    c) Use of mouse    d) Less typing
2)         Command line user interface (CLI)
 A command-line interface provides a place where user types commands for execution. CLI interface is difficult to learn and use. We have to memorize commands. Dos and some versions of Unix and Linux provide command-line interface.

Q7. Define Program and Programming Language

A set of instructions that tell a computer what to do is called program.
A set of words, symbols and codes used to write programs is called programming language.

Q8. Explain different Types of Programming Languages.

There are two main types of computer programming languages.
·        low-level languages
·        high-level languages.
Low Level Languages
These languages are near to computer hardware and far from human languages. Computer can understand these languages easily. Following are two low-level languages:
•     Machine Language      •     Assembly Language
  Machine Language
A computer language in which instructions are written in binary form(0 and 1) is called machine language.
Assembly Language
a)      Assembly language is a low-level language. In assembly language, symbols are used instead of binary code. These symbols are easy to remember.
 High Level Languages
A type of language that is close to human languages is called high level language. High-level languages are easy to understand. Instructions of these languages are written in English-like words e.g. Print, Display, Write etc.
Advantages:
a) Easy to learn and understand    b) Easy to modify    c) Easy to remove errors

Q9. Define Language processor or Translator. Explain different types of Language processors.

Language Processors / Translator
Computer understands only machine language. A program written in high-level or assembly language cannot be run on a computer directly. It is converted into machine language. Language processor or translator is software that converts source programs into machine language(object program). Different types of language processors are: •     Compilers   •     Interpreters     •     Assemblers
Compiler: A compiler is a program that converts the source program into machine language as a whole. A program written in high-level language is called source program. A program in machine language is called Object program.
Interpreter:An interpreter is a program that converts one statement of a program into machine code at one time.
Assembler:An assembler is a translating program that translates the instructions of a program written in assembly language into machine language.

Q10. Differentiate between: Software & Hardware, Source & Object Program, Low-level & High-level Language, DOS and Windows,

Difference between Software & Hardware
Software

Hardware

1.

Software is a set of instructions that tell a computer  what to do

1.

The physical parts of the computer are called hardware

2.

Computer is useless without software.

2

Software cannot run without hardware.

3.

We cannot touch the software.

3

We can touch the hardware.

4.

Hardware is useless without software.

4

Software is useless without hardware.

Difference between Source & Object Program

Source Code

Object Code

1.    Source code is written in high-level or assembly language.

1.

Object   code   is   in   machine language

2.    Source code is easy to understand.

2

Object code is difficult to understand

Difference between Low-level & High-level Language
High-level Language

Low-level Language

1.   High-level languages are easy to learn

1. Low-level languages are difficult to learn.

2.   High-level languages are near to human languages.

2, Low-level languages are far from human languages.

Difference between DOS and Windows
Windows

DOS

1.

It is graphical operating system.

1.

command-line operating system.

2.

It is easy to learn.

 2.

difficult to learn.

3.

It supports multi- tasking.

3.

supports single-tasking.


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Computer Hardware Test Interview VIVA

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Q1. Define Hardware. What are different types of hardware?
The physical parts of a computer are called hardware. Hardware can be touched or seen by us. Different types of hardware components are as follows:
  • Input devices (keyboard, mouse, scanner, digital camera etc.)
  • The Central Processing unit (CPU/Processor)
  • Output devices (monitor, printer, plotter, speaker, data projector etc.)
  • Memory chips (RAM, ROM etc.)
  • Storage devices (hard disk, Floppy disk, CD, DVD etc.)
Q2. Define Input devices.
INPUT DEVICES:Input devices are used to enter data and instructions into computer memory from external world. Examples include: Keyboard, Mouse, Track ball, Track Pad, Joy stick, Touch Screen, Light pen, Touch Screen, Scanner, Digital Camera, Microphone,
Q3. Define Output device.
Output devices:Out put devices are used to display results of processing to the user. They perform the following functions: Examples include: Monitor, printer, plotter, speaker
Printers
Printers are used to produce hard copy out put. They print processing results on paper. Printers are divided into two main categories:
  • Impact Printers
  • Non Impact printers
Impact Printers.
These printers print with striking of hammers or pins on ribbon. For example Dot Matrix printer and daisy wheel printers are impact printers.
Non-Impact Printers.
These printers do not use striking mechanism for printing. They use electrostatic and laser technology. Quality and speed of these printers is better than Impact printers. For example Laser printer and Inkjet printers are non-impact printers.
Q4. Explain parts and working of Central processing unit CPU.
CENTRAL PROCESSING UNIT (CPU)
Central processing unit is the brain of computer. It is also called CPU or processor. Processor is used to process data according to given instructions.
1.            ARITHMETIC LOGIC UNIT (ALU):ALU performs data processing according to given instructions. All computations are done in this unit. ARITHMETIC SECTION of ALU performs arithmetic operations like addition, subtraction, multiplication and division on data. LOGIC SECTION of ALU performs logical operations like comparison between two values.
2.            CONTROL UNIT:Control unit controls all over operations of different parts of computer. For example it takes data and instructions from input unit and stores it into memory. It sends data to ALU for processing.
3.            REGISTERS:A register is a small and temporary memory area in CPU. It holds instruction and data as long as it is being processed. CPU contains a number of registers for example AX, BX, CX, DX etc. A Register may be of 8 bits, 16 bits, 32 bits or more.
Q5. Explain RAM and its types.
Ram stands for random Access Memory. Data in RAM can be accessed directly.. RAM is volatile. Data and programs in RAM are erased when computer is turned off. Therefore RAM is a temporary memory. Ram is also called Primary Memory or Main Memory.
Types of Ram: There are two main types of Ram.
Dynamic Ram (DRAM):Dynamic ram needs to be refreshed frequently. Dram is recharged many times in a second. Therefore, it is slower than SRAM.
Static Ram (SRAM):Static Ram does not need to be refreshed. It is more expensive and faster than DRAM.
Q6. Explain ROM and its types.
ROM stands for Read Only Memory. It is a memory chip fixed on Motherboard. Instructions on RAM can only be read and cannot be changed. The instructions in ROM are written at the time of manufacturing.
PROM:PROM stands for Programmable Read Only Memory. Instructions can be stored in PROM only once. Then it becomes ROM and we cannot change instructions in it.
EPROM:EPROM stands for Erasable Programmable Read Only Memory. Program instructions written on EPROM can be erased and changed.
EEPROM:EPROM stands for Electrically Erasable Programmable Read Only Memory. Program instructions written on EEPROM can be erased with the help of electricity and rewritten.
Q7. Write down notes on the following:
1. Flash Memory            2.            USB Flash Drive 3. Cache memory            4. CMOS
1.         Flash Memory
Flash memory is a form of EEPROM (Electrically Erasable Programmable Read-Only Memory). It is a form of rewritable memory chip that holds its contents without the need of a power supply. The memory is commonly used in memory cards, USB flash drives, MP3 players, digital cameras and mobile phones.
2.         USB Flash Drive memory
A USB flash drive is a flash memory integrated with a USB 1.1 or 2.0 interface. It is used as a small, lightweight, removable and rewritable data storage device.
3.         Cache Memory:A Cache (pronounced “cash”) memory is a small and very fast memory. It is used to speed up the transfer of data and instructions.
4.         CMOS memory:CMOS stands for Complementary metal-oxide semiconductor. It stores configuration information of computer. It is a battery-backed memory chip. It stores the information about disk drives, keyboard, mouse, monitor, current date and time, and other start up information.
Q8. Define storage devices. Explain different types of storage devices.
Storage devices are used to store data and instructions permanently. Storage devices are also called secondary storage devices / backing storage devices / external storage devices or auxiliary storage devices. Secondary storage devices are used because:
Primary/main/internal memory/RAM is volatile and temporary. When computer is switched off, all data in ram is erased.
Storage devices can store large amounts of data and instructions permanently
There are three main types of storage devices:
1. Magnetic Tape    2. Magnetic Disk            3. Optical Disk
1.            Magnetic Tape
Magnetic tape is the oldest storage device. It is made of plastic coated with magnetic material. Data is stored on magnetic tape in the form of magnetic spots.
2.            Magnetic Disk
A magnetic disk is a thin circular metal or plastic disk coated with magnetic material. Data is stored in the form of magnetic spots. Magnetic disk is random access device. It is faster than magnetic tape. There are three main types of magnetic disk:
a. Hard Disk            b. Floppy Disk            c. Zip Disk
a. Hard Disk
The hard disk is also called fixed disk. It consists of one or more metal plates. The plates are fixed in the drive.
Following are major characteristics of hard disk:
  •             The storage capacity of hard disk is much greater than floppy disk.
b.  Floppy Disk
Floppy disk is also called diskette. It is a small plastic plate coated with magnetic material. Data is stored in magnetic spots. Main advantage of floppy disk is that it is used to transfer data from one computer to another. Floppy disk is available in two sizes:
  • 3 ½ INCH Floppy Disk:Storage capacity of micro floppy is 1.44 MB.
  • 5¼ Inch floppy disk.:It is a 5¼ inch diameter plastic plate coated with magnetic material. Its storage capacity is 1.2 MB.
c.         Zip Disk
Zip disk is similar to 3 ½ inch floppy disk. But it can store 100 MB data. Zip disk drive is used to read and write data on a zip disk.                                                                            
3. Optical Disk
LASER technology is used to read and write data on Optical disk. LASER stands for Light Amplification through Emission of Radiation. Laser beam writes on the surface of optical disk by creating very small holes. The presence of hole represents a One and absence of the hole represents a Zero. There are following main types of optical disk.

·         CD-ROM,    DVD,  Rewrite-able optical disk

 CD-ROM:CD-ROM stands for Compact Disk-Read Only Memory. The data stored on Cd-Rom can only be read. It cannot be deleted or changed.
  • DVD - Digital Video Disk
DVD stands for digital Video Disk. It is similar to CD-ROM. It can store up to 17 GB data.
  • Rewrite-able Optical Disks
Rewrite-able optical disk is used to read and write data on the disk. We can not only read data but also change data on disk. Rewriteable optical disks include CD-RW that is CD Rewritable and DVD-RW that is DVD Rewriteable.
Q9. What are commonly used units of measuring storage?

Units of measurement of storage

Bit:Bit is a short for Binary Digit. 0 and 1 are the only binary digits. A bit can hold a 0 or 1.
Byte:A combination of 8 bits is called a Byte.
1 Byte = 8 bits     , 1 KB = 1024 Bytes, 1 MB = 1024 KB, 1 GB = 1024 MB , 1 TB = 1024 GB
Q10.What are Dual Devices? OR What are dual-purpose devices?
The devices that can perform both functions of input and output are called dual devices. For example Hard disk drive, Floppy disk Drive, Magnetic Tape Drive, CD-Writer, Touch screen Monitor etc. These are also called Input/output devices, because they perform both functions.
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