Computer

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3513019022BASIC : Beginners All- Purpose Symbolic Instruction-Code

The computer is defined as an electronic device, which can perform to mathematical, logical and other operations by processing or manipulating information in accordance with a set of instructions called program. In a short, a computer can add, delete, store, chart, compare, analyses project communicates play with information in on its forms at incredible speed.

If we have typed in a list of employees into the computer, and we want to alphabetize the list, the act of placing the names in alphabetical sequence is considered as processing.

Abbreviation of a computer

C:- CalculationO:- OrganizationM:- ManipulationU:- UnderstandingT:- TabulatingE:- EditingR:- Regeneration

The term Computer is derived from Latin word “compute” which means to calculate or manipulate.1. It accepts data (information) from the users and displayed it.2. Computer stores large volume of information in the form of symbols and digits, in its memory

and make available at any time.3. It also performs operations like arithmetic and logical.4. Transfers data, images, sound and graphics through cables at a very fast rate.

Features of Computer

1) Speed

Computer is a very high speed information processing machine. The speed of the computer is measured in terms of Million Instructions Per Second (MIPS). It represents the number of instructions that can be executed by the computer per second.

2) Detailed Instructions

A Computer operates according to the instructions contained in a particular programme and will solve a given problem accordingly. For example, if a programme containing the figures of wages of thousands of workers is fed into the Computer, it will immediately make various calculations and print a wage sheet in no time.

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3) Firmware Firmware is a prewritten program that is permanently stored in read-only memory. Even in the absence of electrical power the memory in ROM stays intact. It configures the computer and is not easily modifiable by the user. BIOS (Basic Input Output Services) instructions are an example of firmware.

4) Live ware People who are associated with and benefited from the computer system are called the live ware. They are (a) System Analysts. Design data processing systems. (b) Programmers. Write programs to implement the data processing system design. (c) Operators. Participate in operating the computers.

5) Procedure

Computer has complex and rigid procedure to operate it. Developing a suitable program is more difficult. The following series of operations is to achieve the desired result.(a) Hardware oriented procedure Details about components and their method of operation.(b) Software oriented procedure Set of instructions required to use software in a computer system.(c) Internal procedure It answers smooth data processing.

6) Versatile Machine

Computer can do a wide variety of jobs through software development. Computer can switch over from one programmed to another according to the set of instructions fed into it. The same computer can be used for accounting work, invoicing, stock control, sales analysis and even for playing chess.

7) Reduced costs

With the ever-increasing advances being made in the state of the art, the cost of computer equipment has dropped drastically over the years. Hardware cost of acquiring their own computer system many now find it not only feasible to acquire a system, but cost-effective as well.

8) Unemployment

Computer performs work speedily and accurately, so big enterprises prefer it. A computer is capable of performing jobs earlier being performed by many people and thus throwing many people out of employment.

9) Storing

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Computer has an in-built memory where it saves data and instructions so that they are available for initial or for additional processing. Such information can be stored in it on a permanent basis on magnetic discs, floppy discs, punched cards or microfilms etc. DVD’s of today can store data of many CDs.

10) Accuracy

Computers can perform all the calculations and comparisons accurately provided the hardware does not malfunction. Computer operations are error-free and as such the information obtained from it is highly reliable. Errors can occur in a computer due to human element. Computer errors caused due to incorrect data or unreliable programs are often referred to as garbage-in-garbage-out (GIGO).

11) Use of special language

The computer dose not understands ordinary language, so specific language: BASIC, COBOL, FORTRAN has been developing for use in the computer.(a) COBOL (Common Business Oriented Language) is used for large data handling purposes in commercial and processing the business information.(b) FORTRAN is a language most suited for processing the mathematical and statistical information.(c) BASIC is used by the persons who have just started to learn the programming.(d) LOGO (Logic Oriented Graphic Oriented) is mainly developed for children. It helps them learn basic mathematical and geometric skills easily.(e) C++ is used effectively in developing system software as well as application software.(f) JAVA or OAK is designed for the development of software for consumer electronic devices.

12) Use of Binary System

Binary means pertaining to a pair. Binary numbering system is one which has a base of 2 represented by the digits 0 and 1. (In contrast to this binary system our extensively used decimal system has a base of 10, represented by the digits 0-9.)

Conversion of decimal number 20 into Binary Digits.

Operation Quotient Remainder

20/210/25/22/21/2

105210

00101

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The process will be continued till the Quotient becomes 1 or 0. Finally, we shall be writing last Quotient first and remainders in the reverse order, i.e., from bottom to the top. Thus, for the decimal number 20, the binary number will be 010100.

13) Computer is different from a Calculator

a) Calculators can work only with numbers, but computers can work with both numbers and words.b) Calculators can’t perform logical operation, but computers can.c) Calculators don’t have permanent storage media, but computer stores large volume of data in its memory and reproduce any part of it, as and when needed.d) Calculators are less fast compare to computers.e) Calculators can’t be programmed very effectively, but computers can.f) Calculator can’t store program.h) Intermediate data can’t be stored and used later, but computers can.i) Calculators need human beings to interfere in its operations, but no human assistance is needed after the programmed goes for execution.

14) Computer is different from people

a) Computers are faster than people.b) Computers are more accurate when dealing with large numbers.c) Computers simply don’t board and can perform the same operation over and over again over any length of time.d) Computers are not flexible like human life. A Computer must have every step describe and computers can’t think.e) Computers can’t do anything itself. It can do only what is instructed to do.f) To memories figures is difficult for human beings but not for a computer.

APPLICATIONS OF COMPUTERS

In human affairs we have reached a point where the problems we must solve are no longer solvable without the aid of computers. I fear not computers, but the lack of them.

1. Applications in Accounting or Business

a) Recording and posting business transactions.b) Processing and maintaining payrolls.c) Maintaining personnel records.d) Keeping effective stock control.e) Invoicing of sales.f) Preparing bills and debtors accounts.g) Maintaining purchases and sales ledger.h) Classification of accounting transactions through sorting, merging and updating.i) Reporting in the form of Trial balances and ledger balance and Balance sheet.

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2. Applications in human lives

a) Computers are useful for everyone. Parents can be using a computer to records for their daily expenditure and income. Also recording important dates like birthdays, marriage anniversaries etc.b) Telephone bills are generated by the computer. Telephone complaints are entered into computers to have better control on how many complaints are attended to in a day. Telephone inquiries have been computerized so that instant information is available to the customers.c) Students can use a PC to prepare notes and project, expect information from the Internet, take online test etc. In examination for checking papers etc. d) In office, they are also maintaining the all type records, workers details, manufacturing products like automobiles, shoes, computer cabinets etc. Creation of blueprints for houses.e) In developing country like India one of the reasons for people to go for PC is the E-mail facility, since this is the most convenient, fastest and cheapest ways to communicate with friends, family members and acquaintances within and outside the country.f) Hotel room bookings are done on the computer. This enables the person dealing with bookings to get quick information on the availability of rooms.g) Offices and organization use the computers to increase their productivity and profits.h) The advertisements that we see have a plethora of graphics in them. All these are computer generated. It also offers scope for games, music and even comic that adds to our entertainment.

3. Applications of Spreadsheet

A spreadsheet is highly interactive computer program that accepts data in a tabular form (in rows and columns) and allows user to manipulate/calculate/analyze data in the desired manner, displayed on-screen in a scrollbar window.

Sales: A marketing agency could use it to formulate and evaluate schemes for the items to be sold. In Sports: Individual and team statistics can be kept in spreadsheet. Home Usage: A home user can use a spreadsheet to plan expenditure, maintain daily accounts, and maintain dates of insurance premiums and installment payments. Accounting: They are used to create general ledgers, trial balance sheets and profit and loss accounts on the computer. Payroll: Payroll details can be maintained in it like basic salary, Leave Travel Allowance (LTV), Dearness Allowance (DA), House Rent Allowance (HRA), tax to be paid, gross salary and net salary.

Features of Spreadsheet

Spreadsheets cannot only represent data values but also their relationship(s). Spreadsheets provide facilities of cutting, pasting, moving, copying data values or formulae

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Or formats etc. What if analysis becomes very easy using spreadsheets. Numerous built-in functions are available in spreadsheets. Data can graphically be represented through charts/graphs of many types.

4. Applications of Word Processor

A Word Processor can be defined as a computer program that enables you to type, modify, print, and save texts for future retrieval and revisions. Some popular word processors are Microsoft Word, WordStar, WordPerfect, Soft word etc. You can use a word processor to perform Repetitive tasks like typing: Circulars, Public notices, Memos, Prospectus for colleges.Time consuming tasks like creating: Reports, Tenders, Contracts, Agreements.General Correspondence: Newsletter, Memos.Tabular Reports: Time tables, Work Schedule, Balance Sheets and Report cards.

5. Applications of Multimedia

A multimedia application is an application concerned with the computer-controlled integration of text, graphics, drawings, still and moving images (video), animation, sound/ audio. With multimedia you cana) Add sound to files or tasksb) Create 3D effects in different ways.c) Build a business presentation that includes corporate presentations, sales presentations.d) Create animated birthday cards for your friends who have computers.e) Learn a new language by interacting with the written and spoken words.f) Do scientific research- a scientist can look at a molecular model of a particular substance and manipulate it to arrive at a new substance.g) Do engineering for designing a machine or an automobile. This is known as computer-aided design (CAD).h) Doctors can simulate how the human body is affected by diseases spread by viruses and bacteria and then develop techniques to prevent the same.i) Hypermedia, e.g. World Wide Web (WWW). An article on World War II can include hyperlinks to articles on countries involved in the war.j) Improve quality of games, kiosks, digital publications, electronic reference materials, museum exhibitions and more.

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Generation of Computers

1. 1st generation of computers:- (1942-1954)

a) In this generation was the use of vacuum tubes.b) Vacuum tube technology made possible the advent of electronic digital computers.c) Magnetic drums were used for memory.d) Punched cards were used for input and output.e) Perform computations in milliseconds.f) Manual assembly of individual components into functioning unit required.g) Big and clumsy computers.h) Electricity consumption was high, electric failure occurred regularly- computers not very

reliable.i) Large air conditioners were necessary because the computers generated heat.j) Programming in machine language.k) Single user capability.l) Lower system software.Ex: - IBM (International Business Machine Corporation) 701, IBM 350 etc.

2. 2nd generation computers:- (1954-1964)

a) These computers are fully transistorized instead of vaccum tube. Transistor does the same functions as that the vaccum tube but very small size compared to vaccum tube.

b) Generated less heat, more reliable.c) Reduced computational times from milliseconds to microseconds.d) Core memory developed.e) Magnetic tapes and disks were used for secondary memory. f) First operating systems developed.g) Programming in machine language as well as assembly language.h) Relatively fast and the speed was 2 Mega operations Per Second.Ex: - IBM 1401 etc.

3. 3rd generation computers:- (1965-1974)

a) These computers used IC’s technology and integrated Circuit on silicon chips, it consist of 1000 of transistors.

b) Minicomputers were introduced.c) High-level languages appeared.d) Highly sophisticated technology required for the manufacture of IC chips.e) Reduced computational times from microseconds to nanoseconds.f) More programs can be run.

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g) Require less power. Ex: - IBM 370, Spectra 70 etc.

4. 4th generation of computers:-(1975-1984)

a) These computers used microprocessor technology. It contain entire processing unit on a single chip. It made-up of 1000 of transistors and other semi-conducting device.

b) Very high speed of the order of greater than 100 operations per second.c) Highly sophisticated technology required for the manufacture of LSI chips.d) Integrated circuits, smaller and faster.e) Micro computer series such as IBM and APPLE developed.f) Portable computers developed.g) Great development in data communication.h) Different types of secondary memory with high storage capacity and fast access developed. Ex: - DEC 3090 etc.

5. 5th generation of computers :-( 1985-onwards)

The main specialty being the use of parallel. The logic used as very large scale integration (VLSI). The speed operations orders are 100 mega operations per second. The other concepts like data processing, information processing, knowledge processing and distribution processing are being considered under this generation.The latest generation computers in this year will photogenic computers. These computers will work 1000 of time faster than the best possible for electronic computers.

a) Advancement in networking technology.b) Development of storage technology and supercomputers.c) Development of robots to assist human beings.d) Parallel-processing-many processors are grouped to function as one large group

processor.e) Superconductors – a superconductor is a conductor through which electricity

can travel without any resistance in faster transfer of information between the components of a computer.

History of Computers

Stone Age

In olden days people didn’t have the awareness of counting. In other words usage of mathematics has almost nil during that time because he started to learn counting by stones.

Abacus

Abacus is considered to be the first computer and was invented 5,000 years ago by the Chinese.The basic purpose of the device is to make calculations.

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It consists of a rectangular frame with a number of strings attached.Each string has a collection of beads. These beads are used to perform calculations.Abacus is used even today to teach small children how to count.

Babbage’s Mechanical Computer

Charles Babbage invented the first mechanical computer during the period 1830 to 1850.This computer performed basic arithmetic functions. He is referred to as the ‘Father of computers’ due to his pioneering work. It had the following five components:A storage unit that holds the numbers.An arithmetic unit, called Mill, to perform the arithmetic calculations.A control unit that controls the activities of the computer.An input device that gives the numbers and instructions to the computer.An output device that displays the result.

Napier’s ‘Logs’ and ‘Bones’

John Napier developed the idea of logarithm. He used ‘logs’ to transform multiplication problem to addition problem. Napier’s log later became the basis for a well known invention-the computing machine known as ‘Slide rule’. He also devised set of numbering rods known as Napier ’s bones. He could perform both multiplication and division with these ‘Bones’. The idea of logarithm, developed in 1614, notably reduced the tedium of repetitive calculations.

PASCAL’s adding machines (1642)

Blaise Pascal, a French mathematician, invented the first adding machine (also known as Pascaline) in 1642 made up of gears which was capable of addition and subtraction. It worked on clock work mechanism principle. The adding machine consisted of numbered toothed wheels having unique position values. The rotation of wheels controlled the addition and subtraction operations. This machine was capable of carry-transfer automatically.

Leibnitz’s Calculator

Gottfried Leibnitz, a German mathematician, constructed a new machine in 1671 that was able to perform multiplication and division as well. This machine performed multiplication through repeated addition of numbers. This machine used stepped cylinder each with nine teeth of varying lengths instead of wheels as was used by Pascal.

Punched Cards

The next device that contributed to the evolution of the computers was the punched cards.These were cards made of special pulp paper. Machines were used to make holes in the card and thus store information. In addition, sorting machines were used to read these cards and collect data.

Types of Computers

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Computers can be classified on the basis of Size, Cost, Performance, Speed of processing, Storage capacity, Ability to handle input and output devices as follows:

Workstation (or Nodes)

Workstation refers to the computers that are attached to a network and are seeking to share the resources of the network. A computer becomes a workstation of a network as soon as it is attached to a network. The most common operating systems for workstations are UNIX and WINDOWS NT. Of course, if there were no nodes, there would be no network at all.They are typically found in desktop publishing, software development, industrial and business environments that require high levels of computational abilities.

Server

A computer that facilitates the sharing of data, software, and hardware resources (e.g. printers, modems etc) on the network is termed as server. A network can have more than one server that allows workstations to share specific resources. A file server serves files –related requests like storing files, deciding about their access privileges and regulating the amount of space allowed for each user. The print server takes care of the printing requirements of a number of workstations and the modem server helps a group of network users use a modem to transmit long distance messages.

Supercomputers

Supercomputers are the largest and fastest computers. They are also the costliest computers.They are used in fields like science and defense. These computers are used for designing and launching missiles, weather forecasting, biomedical research, aircraft design and automobile design.There are only a few supercomputers throughout the world. IBM’s Blue Gene is considered by many to be the fastest computer in the world. India owns a series of supercomputers called PARAM developed by C-DAC.

Mainframes

Mainframes are more powerful than minicomputers.They have high processing speeds and can store large amounts of data. They are used in wide area networks and support hundreds of users. However, these computers consume more electricity.Insurance companies use mainframes to process information about millions of policyholders.Some examples are IBM 3000 series and Univac 1180.

Minicomputers

Minicomputers, also known as midrange computers, are small general-purpose computers. These computers can perform more complex tasks and cost more than microcomputers.They are larger in size and they have small to medium storage capacity.

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They are used for processing data and analyzing results of experiments. They are also used for controlling and monitoring production processes.Some examples are PDP 11/42 and VAX 11.

Microcomputers

Microcomputers are the least powerful, yet the most widely used and fast-growing, type of computer. They are also called personal computers (PCs). Individuals as well as organizations use these computers. These computers use microprocessors.They are small in size. Also, they do not have large storage capacities.They can perform difficult tasks. They are mainly used for desktop publishing, accounting, statistical analysis, graphics designing and project management.Some examples are APPLE II, IBM PC, PS/2 and Macintosh.Types of microcomputers:The difference between portables and desktops is that portables can be carried while traveling unlike desktops. Laptops, Notebooks, Palmtops are portable computers.Desktops are small enough to fit on top of or alongside a desk yet are too big to carry around.Laptops are small-sized machines that have the same power of a desktop. They are expensive than desktop. The weight of a laptop is around 3 to 5 kg. It may be either AC-powered, battery powered or both. The drawback of a laptop is that it is too bulky. Examples: Toshiba 5200C and SLT/286.Notebooks are smaller than a laptop and are designed to overcome the drawbacks of a laptop. They are lightweight, and fit into most briefcases. They have the size of a notebook but are as powerful as a desktop. They are more costly when compared to laptop. They weigh 2 to 3 kg. Examples: contura 3/20 and AcerAnyWare.A table PC is a type of notebook computer that accepts your handwriting. This input is digitized and converted to standard text that can be further processed by programs such as a word processor.Handheld computers, (or palm computers) are the smallest and are designed to fit into the palm of one hand. These systems typically combine pen input, writing recognition, personal organization tools, and communications capabilities in a very small package.Palmtops or PDAs (Personal Digital Assistant), have the size of a pocket calculator. They are not as powerful as a desktop. It can do Word processing, Spreadsheet calculations, handwriting recognition, game playing, faxing and paging. Example 3Com’s Palm V.Wearable computers is very small so that it can be worn the body itself. It has smaller processing power. It finds its application in the field of medicine. For e.g. pacemaker to correct the heart beats. Insulin meter to find the levels of insulin in the blood.

NETWORKS

A network is defined as an interlinked collection of computers by means of a communication system. In simple terms, two computers are said to be interconnected if they are capable of exchanging information. Man has a need to communicate with people in different places. Business people have to exchange information with others around the world. So, networking of computers is very essential. The most significant effect of computer networking is that they form a huge information chain that ensures that information is available to users at the time and location where they need it.

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Advantages of networks are:

Resource sharing reduces the costs. It includes:Share resources - such as printers and scanners. This is cheaper than buying equipment for each computer.Share storage – being able to access files from any machines on the network can share data.Share software- software can be installed centrally rather than on each machine. Metering software can than be used to limit the number of copies being run at any one time. This is much cheaper than buying licenses for every machine.Reliability-A file can have its copies on two or more computers of the network, so if one of them is unavailable, the other copies could be used.Fast Communication- With networks, it is possible to exchange information at very fast speeds.Access to remote database- It is easy to for the average person sitting at his PC to make reservation for airplanes, trains, hotels and so on anywhere in the world with instant confirmation.

Disadvantages of networks are:

The systems are more sophisticated and complex to run. This can add to costs and you may need specialist staff to run the network.If networks are badly managed services can become unusable and productivity falls.If software and files are held centrally, it may be impossible to carry out any work if the central server fails. People become reliant on the communications, if these fail it can cause havoc.File security is more important especially if connected to WANs e.g., protection from viruses.

A network can either be a small group of five computers linked together or a high- end network that links hundreds of computers spread across the globe. Networks vary depending on size, complexity and geographical spread. Based on geographical spread, networks can be classified as

Local Area Network (LAN)

LANs are confined to a localized area such as an office. It is a form of computer communications generally used for the internal transfer of data and information within an organization. For e.g. the type of network in our school is LAN.LAN provides two benefits: economy and flexibility. People can share costly equipment. For instance, four microcomputers share the laser printer and the file server, which are expensive pieces of hardware.

Metropolitan Area Network (MAN)

MAN computers extend within the city or the metropolitan area. For e.g. to connect five branches of a school in a city, you would need a MAN. MANs span distances up to 100 miles.

Wide Area Network (WAN)

WANs are spread across the entire world. They are used to link computers across the globe.

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A WAN can also connect individual LANs to create one integrated huge LAN. Majority of the WANs use satellites to facilitate efficient communication. High-speed WANs link remote computers effectively to reduce costs and to complete work faster. For e.g. to connect different branches of a school in different countries, you would need a WAN.

NETWORK COMPONENTS

Typically, all networks consist of a server, client, media and resources.Node – Any device that is connected to a network. It could be a computer, printer, or data storage device.Client – Client refers to the set of computers that access shared network resources provided by the server. Typically, a client is a user’s microcomputer.Server – A server is a computer that facilitates the sharing of data, software, and hardware resources (e.g., printers, modems etc.) to other computers present on the network.Media: Media is the way in which the computers are connected.Resources: Resources are files, printers, etc. used by network users.Network interface cards (NIC) – These are expansion cards located within the system unit that connect the computer to a network. Sometimes referred to as a LAN adapter.

Electronic mail (e-mail) - a system whereby a computer user can exchange messages and files with other computer users (or groups of users) via a communication network-is one of the most popular uses of the internet. This facet of the Net was one of the first applied uses, and continues to be a powerful communications tool.

Advantages of E-mail

Fast- Electronic mail can be delivered almost as fast as the wire can carry it anywhere around the world. Timely buying and selling decisions can be made.Cheap- Transmission usually costs nothing, or at the most, very little. Compared to telephone calls, faxes, or overnight courier service, Email is less expensive.Simple- Easy to use, after initial set-up. Your proposal can be answered, revised, stored, and sent to others, all without reams of paper involved.Efficient- Sending to a group can be done in one step.Versatile- Pictures, PowerPoint or other files can be sent too.Waste Reduction- E-mail goes a long way towards reducing the clutter of paper in the modern office, not to mention saving many trees.Record Maintenance- Because all messages are files, you can automatically maintain a record of communications with someone else. Patience- E-mail waits until you read it. It does not have the jangling urgency of a phone call.

Disadvantages of E-mail

Lack of computer knowledge among people, so not sure all receiving parties use email system.Unwanted SPAM emailsIllegal contents including VIRUS damages end user systems, data and reputation.

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Email might not send due to loss of connection to the internet. You have to be at a computer to read or print e-mail.

INTERNET

The internet is a worldwide network of computers, using a common protocol (TCP/IP or Transmission Control Protocol/Internet Protocol) to communicate with each other. This language acts as medium of communication among numerous Internet computers. These computers possess software to provide or serve information and/or to request and see information. Academic, Commercial, Governmental, and military networks are part of the Internet. Through telephone wires and satellite links, Internet users can share information in a variety of forms. The size, scope and design of the internet allow users to:Connect easily through ordinary personal computers and local phone numbers;Exchange electronic mail (e-mail) with friends and colleagues with accounts on the internet;Post information for others to access, and update it frequently;Access multimedia information that includes sound, photographic images and even video; and access diverse perspectives from around the world.

How does internet work?

In internet, most computers are not connected directly to the internet. Rather they are connected to smaller networks, which in turn are connected through gateways to the internet backbone.A gateway is a device that connects dissimilar networks. It establishes an intelligent connection between a local network and external networks with completely different structures. A backbone is a central interconnecting structure that connects one or more networks just like the trunk of a tree or the spine of a human being.

Advantages of Internet

Sharing research and business data among colleagues and like-minded individuals.Communicating with others and transmitting files via e-mail.Requesting and providing assistance with problems and questions.Marketing and publicizing products and services.Gathering valuable feedback and suggestions from customers and business partners.

Difference between internet and intranet

The internet is a worldwide network of computer networks around the Globe. Internet uses a set of protocols called TCP/IP. Internet is not owned by anybody. Each person owns the part of the internet he uploads data to. On the other hand Intranet is network, which is privately owned. Intranet also uses same set of protocols as Internet.

Applications of Internet

Searching online jobs,Learning a foreign language,

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Making friends from any part of the worldParticipating in a discussion about your favorite TV show with similar minded people across the world,Send to a friend, an electronic birthday card which actually sings ‘Happy Birthday to you’Find out which are the current most popular computer programming languages in the industry,Visit an electronic zoo or a museum,Download (obtain) some interesting software and try it out.Make your own home page which talks about yourself, your family, your pets and your hobbies,Chat with a friend working abroad and see him as you talk.

Protocols

A protocol means the set of rules that are applicable for a network or we can say that the common set of rules used for communication in a network. It is a formal description of message formats and the rules that two or more machines must follow to exchange those messages. Protocol defines standardized formats for data packets, techniques for detecting and correcting errors and so on.

Illustration

Let us assume that A and B need to talk to one another. They want to exchange their ideas. They start talking again simultaneously, then pause for breath simultaneously, and then start talking again. To avoid this confusion, they must follow a common set of rules while talking, known as communication protocol for A and B., say first A must talk, then he must give B a chance to put forward his ideas and so on.

Types of Protocols

FTP (File Transfer Protocol)

This protocol is mainly concerned with transfer of file from one system to another on internet provided that permissions are set accordingly. FTP offers these advantages:It is very useful to transfer files from one network in an organization to another.It is an effective way to get a geographically dispersed group to co-operate on a project.It is a potent and popular way to share information over the internet.The objectives of FTP are:To promote sharing of files (computer programs and/ or data);To encourage indirect or implicit (via programs) use of remote computers:To shield a user from variations in file storage systems among hosts; and To transfer data reliably and efficiently. FTP, through usable directly by a user at a terminal, is designed mainly for use by programs.

TCP/IP (Transmission Control Protocol/Internet Protocol)

TCP is responsible for making sure that the commands get through to the other end. It keeps track of what is sent, and retransmits anything that did not get through. Generally, TCP applications use four layers:

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An application protocol such as mail.A protocol such as TCP that provides services need by many applications.IP, which provides the basic service of getting datagram to their destination.The protocols needed to manage a specific physical medium, such as Ethernet or a point to point line.

HTTP (Hypertext Transfer Protocol)

The HTTP protocol consists of two fairly distinct items: the set of requests from browsers to servers and the set of responses going back to the other way. Messages are passed to HTTP in a format similar to that used by Internet Mail and Multipurpose Internet Mail Extensions (MIME).The HTTP has various built-in request methods which allow users to read a web page, or to read a web page’s header, or to store a webpage, or to append to a named resource, or to remove the web page or to connect two existing resources or to break an existing connection between two resources.

SLIP/PPP (Serial Line Internet Protocol/ Point to Point Protocol)

SLIP/PPP provides a form of direct Internet connection in the sense that:The home user’s computer has a communications link to the internet even if it is via a service provider (ISP).The home user’s computer has the networking software that can speak TCP/IP with other computers on the Internet.The home user’s computer has an identifying address (IP address) at which it can be contacted by other computers on Internet.

Cyber Crime may be defined in a general way as an unlawful criminal activity where the computer or network is tool, source, target, or place of a crime.Cyber law is a generic term, which refers to all the legal and regulatory aspects of internet and the World Wide Web.

Types of Cyber Crime

Unauthorized access: is when a person who doesn’t have permission to connect to or use a system gains entry in a manner unintended by the system owner. The popular term for this is “hacking”. Hackers are more interested in gaining knowledge about computer systems and possibly using this knowledge for playful pranks.

Cracking: means, ‘illegal accesses. Now, access comprises the entering of the whole or any part of a computer system (hardware, components, stored data of the system installed, directories, traffic and content-related data. Crackers are the malicious programmers who break into secure systems.

Email bombing: or spam refers to sending a large amount of emails to the victim resulting in the victim’s email account or mail server crashing.

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Data diddling: This kind of an attack involves altering the raw data just before it is processed by a computer and then changing it back after the processing is completed.

Salami attack: This attack is used for the commission of financial crimes.

Logic bomb: It is the code embedded in a legitimate program that is to set to explode when certain conditions are met.

Virus/worm attack: This attack can infect other program by modifying them. The modification includes a copy of the virus program, which then goes on infecting other program.

Trojan attack: It is an apparently useful program containing hidden code that when invoked, performs some unwanted or harmful functions.

Cyber pornography: This would include pornography websites; pornographic magazines produced using computers and the Internet.

Email spoofing: A spoofed email is one that appears to originate from one source but actually has been sent from another source.

Intellectual Property Crime: This includes software piracy, copyright infringement, trademarks violations etc. Cyber Stalking: involves following a person’s movements across the Internet by posting messages (sometimes threatening) on the bulletin boards frequented by the victim, entering the chat-rooms frequented by the victim, constantly bombarding the victim with emails etc.

Online investment newsletters: Many newsletters on the internet provide the investors with free advice recommending stocks where they should invest. Sometimes these recommendations are totally bogus and cause loss to the investors.

Bulletin boards: This is a forum for sharing investor information. Fraudsters often find it easy to spread bogus investment schemes or spread false information about a company; causing loss of millions who bank on them.

Security related crimes: Confidential information can reside either on the physical stored media, such as hard drive or memory or it can reside in the transit across the physical network wire in the form of packets. These two information states provide opportunities for attacks from users on the internal network, as well as users on the internet.

Network packet snifters: A packet snifter is a software application that uses a network adapter card in a promiscuous mode. To capture all network packets that is sent across a local network. A third party can easily interpret the network packets and develop a packet snifter because they are not encrypted.

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NETWORK SECURITY

The problems encountered under network security can be summarized as follows:Physical security holes: When individuals gain unauthorized physical access to a computer and temper with files. Hackers do it by guessing passwords of various users and then gaining access to the network systems.Software security holes: When badly written programs or ‘privileged’ software are compromised into doing things that they should not be doing.Inconsistent Usage holes: When a system administrator assembles a combination of hardware and software such that the system is seriously flawed from a security point of view.

PROTECTION METHODS

Authorization: determines whether the service provider has granted access to the web service to the requestor. Basically, authorization confirms the service requestor’s credentials. It determines if the service requestor is entitled to perform the operation, which can range from invoking the web service to executing a certain part of its functionality. Authorization is performed by asking the user a legal login-id. If the user is able to provide a legal login-id, he is considered an authorized user.

Authentication ensures that each entity involved in using a web service- the requestor, the provider, and the broker (if there is one) - is what it actually claims to be. Authentication involves accepting credentials from the entity and validating them against an authority. It is also termed as password-protection as the authorized user is asked to provide a valid password, and if he is able to do this, he is considered to be an authentic user.

Encrypted Smart Cards

Passwords in a remote log-in session generally pass over the network in unencrypted form; any hacker (or cracker) can simply record it and can use it later maliciously to corrupt data/files or to harm anyone etc. To counter such threats, newer approaches are suggested such as encrypted smart cards. An encrypted smart card is a hand-held smart card that can generate a token that a computer system can recognize. Every time a new and different token is generated, which even-though cracked or hacked, cannot be used later.

Biometric systems

The biometric systems involve some unique aspect of a person’s body such as finger-prints, retinal patterns etc. to establish his identity.

Cookies

A cookie is a message that a web server transmits to a web browser so that the web server can keep track of the user’s activity on a specific web site. Cookies cannot read your hard drive to find out information about you; however, any personal information that you give to a web site, including

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credit card information, will most likely be stored in a cookie unless you have turned off the cookie feature in your browser. In this way only cookies a threat to privacy.

Firewall

The system designed to prevent unauthorized access to or from a private network connected to the internet, especially intranet is called firewall. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.

Firewall Techniques

Packet filter Looks as each packet entering or leaving the network and accepts or rejects it based on user-defined rules. It is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.Application gateway Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose performance degradation.Circuit-level gateway Applies security mechanisms when a connection is established. Once the connection has been made, packets can flow between the hosts without further checking.Proxy server Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses.

More Security Tips

Use strong passwords.Use virus protection software.Do not keep computers online when not in use.Make regular back-up of critical data.

BIT AND BYTE

The number of characters that can be stored in a computer is called the storage capacity of the computer. Bit is the smallest unit of measurement of storage capacity. A collection of eight such binary digits is called a byte. Typically, a byte or a collection of eight bits is used to store one character in computer’s memory, including numbers(0-9), alphabets(A-Z), symbols and other characters (#, {}, ‘, ~, ^ ). A computer uses binary system, only two digits, 0 and 1, to represent these characters. The 0’s and 1’s in binary system are known as bits (binary digits).

Units of memory

4 bits – 1 nibble8 bits – 1 byte1024 bytes – 1 kilo byte1024 kilo bytes – 1 mega byte1024 mega bytes – 1 giga bytes1024 giga bytes – 1 tera bytes.

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Internal storage (Primary memory)

Memory is a holding area for data, instructions, and information. The primary memory of a computer stores the data provided by the user and the instructions provided by the programs.The primary memory is placed on the motherboard in the form of chips. They are of two types:

Random Access Memory (RAM)

Whenever a computer receives any information, it stores it in the RAM. Input data is stored in this memory before it goes to the processor for actual processing. The storage capacity of RAM may vary in different computers. The characteristics of RAM are:▪You can read the contents of a memory location or write new contents into it. Hence, RAM is also called Read and Write Memory.▪RAM is volatile, because information stored in RAM is lost when the computer is switched off.

Read Only Memory (ROM)

Read only memory (ROM) contains all basic instructions that are needed for starting a computer, give keyboard keys their special control capabilities, and put characters on the screen.The characteristics of ROM are:▪ “Read only” means that the CPU can read, or retrieve, data and programs written on the ROM chip. However, these instructions cannot be erased or modified. They can only be executed.▪Information stored in ROM is not lost if the computer is switched off. Hence, ROM is non- volatile.

Programmable Read – Only Memory (PROM)

PROM is a memory chip on which data can be written using a special device called PROM programmer or PROM burner. Once written, the program remains on the chip forever even after the computer is switched off. Erasable Programmable Read - Only Memory (EPROM) is a special type of PROM, which can be erased by exposure to ultraviolet rays.

Note : Both RAM and ROM are referred to as Immediate Access Storage(IAS) because CPU can access the data so quickly compared to data in baking storage( the secondary memory).

External storage (Secondary memory)

This is used to store information permanently. To do so, you use the external storage media. Some important characteristics of secondary storage include:-Media are the actual physical material that holds the data and programs.Capacity measures how much a particular storage medium can hold.Storage devices are hardware that reads data and programs from storage media. Most also write to storage media.Access speed measures the amount of time required by the storage device to retrieve data and programs.

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The various devices that are used for storage are the following:

Cartridge Tape

Cartridge Tape is a storage medium that is used to store large amounts of data. Its appearance is similar to a video cassette. It is a cheap and reliable storage device. It is used in large machines. However, retrieving data from a cartridge tape takes time.

Magneto- Optical disk

The storage capacity of a magneto- optical disk is high. Computers can read and write onto a magneto- optical disk. The speed of data retrieval is very fast. Also, the data in this disk is less prone to damage.

Floppy Disk

Floppy disk is a magnetic storage device that is used to transfer files between computers and to store data/information as backup. It contains a single flat piece of circular plastic (the disk) coated with metal oxide and enclosed in vinyl or plastic cover. The most commonly used floppy disk is 3.5 inches with a storage capacity of 1.44 MB and is of double sided high-density capacities (135 tracks per inch). Double -sided indicates that data can be stored on both sides of the disk. Density refers to how tightly the bits (electromagnetic charges) can be packed next to one another.

Advantage:

Used to move data from one location to another.Inexpensive, Reusable.

Disadvantage:

Not very strong-easy to damage, Small storage capacity.Quite slow to access and retrieve data.

Precautions:

Never bend the floppies. It may cause physical damage and hence loss of data.Always keep the floppies inside a paper cover. Do not expose it to dust or heat.

Hard Disk

The hard disk is located in the system unit. It is made up of a collection of disks known as platters. These platters are sealed in a vacuum disk and located in the system unit. Whenever you save data in a computer, it is stored on a hard disk. Also, when you copy data from a floppy disk to the computer the data is saved on the hard disk. Hard disk has the capacity to store huge amounts of data. Hard disks store and organize files using tracks, sectors and cylinders.

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Concentric circles on the magnetized surface of the magnetic disks are known as tracks.The tracks on the disk surface are divided into invisible segments known as sectors.Similar numbered tracks on different platters of a hard disk form a Cylinder.

Floppy Disk Hard Disk

Floppy disks are also called floppies or micro disks.

Hard disks are also called fixed disk.

The computer takes more time to read from a floppy disk.

The computer takes less time to read from a hard disk.

More prone to damage by heat, dust and improper handling as it is made of a flexible material.

Less prone to damage as it is within the system unit.

Can be used to store 1.44 MB of data. Can be used to store far more data than floppy disks. They can be used to store data in the range of a few GBs.

Inexpensive Costly

CD-ROM (Compact Disk Read Only Memory)

Compact disc is an optical storage device that has a huge storage capacity. The advantage of a CD-ROM is that the data present in it is less prone to damage. It is a removable and is a read only memory. Being read only, the data present in a CD-ROM cannot be changed and is mainly used to record information including text, graphics or audio on the CD distribution e.g., encyclopedias, software, games, e-books etc.To read a CD-ROM a device called CD-ROM drive is needed. Any information or data on CD-ROM can be erased or written onto with the help of a special device called CD-Writer.

DVD (Digital Versatile Disk)

DVD is an optical storage device that looks the same as a compact disc but is able to hold about 15 times as much information and transfer it to the computer about 20 times as fast as a CD-ROM.A DVD, also called a Super Density Disk (SD), can hold up to 17 gigabytes of data or four hours of movies on a side.

Disk Drives

The computer has a special device to read from and write to the storage media. This device is called the disk drive. It is a part of the system unit. The disk drive performs the function of reading data from the disk as well as writing data to the disk. Hence, disk drive is an Input-Output device. The drive for a floppy disk is called the floppy drive. You can read and write information to a floppy disk using the hardware device called the floppy drive. Floppy drives and hard drives are examples of input and output devices as the CPU can read from and write onto them. The drive used to read from a CD-ROM is called the CD-ROM drive.

DISTINCTION BETWEEN HARDWARE AND SOFTWARE

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Points of Difference

Hardware Software

Meaning The internal components of the PC and the various input and output devices that can be attached to PC are called as the hardware.

Software constitutes the logical program that handles the different components of our PC and helps them to interact with one another in a handle- free manner. The words program or application or software is all used interchangeably.

Uses The same hardware is used for performing different jobs. Machines or hardware do not require changes for different works.

The different software is used for performing different jobs.

Physical Construction

Hardware has physical construction. It can be seen and touched.

Software does not have physical construction. It can neither be seen nor touched.

Examples Keyboard, Monitor, Mouse, System units and also additional hardware components that can be added to our system are the modem, printer, scanner etc.

Customized software pertains to the requirements of a specific user for whom the software has been developed. General software is developed keeping in mind general specifications of a problem-Excel, Word, Oracle, DTP packages etc.

TYPES OF SOFTWARE

Software represents the set of programs that govern the operation of a computer system and make the hardware run. There are broadly two categories of software:System Software controls internal computer operations so that components of system function properly. System software is not a single program. Rather it is a collection or a system of programs that handle many of the technical details related to using a computer with little or no user intervention. It includes following four types:a)Operating System. An operating system is a program which acts an interface between a user and the hardware (i.e., all computer resources). Windows XP, Windows Vista, and the Mac OS X are three best- known operating systems for today’s microcomputer users. It performs the following functions:-It facilitates operation of hardware by its user.It manages the various input-output devices of the computer.It supervises all the activity of the computer.It allocates the devices whose services the user requests for.b) Utilities are specialized programs designed to make computing easier. It can make your computer faster, safer and more productive. For e.g. Windows utility called Disk Defragmenter locates and eliminates unnecessary file fragments and rearranges files and unused disk space to optimize computer operations. The most essential utility programs are:-

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Troubleshooting or diagnostic programs recognize and correct problems, ideally before they become serious. Disk Cleanup is a troubleshooting utility that identifies and eliminates nonessential files. This frees up valuable disk space and improves system performance.Antivirus Programs that guard your computer system against viruses or other damaging programs that can invade your computer system.Uninstall programs that allow you to safely and completely remove unneeded programs and related files from your hard disk.Backup programs that make copies of all files or selected files that have been saved onto a disk to be used in case the originals are lost or damaged. It helps to protect you from the effects of a disk failure.File compression programs that reduce the size of files so they require less storage space and can be sent more efficiently over the internet.c) Device drivers:- Every device, such as a mouse or printer, that is connected to a computer system has a special program associated with it. Device drivers are specialized programs that allow particular input or output devices to communicate with rest of the computer system. Each time the computer system is started, the operating system loads all of the device drivers into memory. Whenever a new device is added to a computer system, a new device driver must be installed before the device can be used.d)Language Processor. Translate source program into machine language. E.g. Interpreter, Compiler, Assembler. An interpreter converts and executes an HLL (High Level language) program into object program line by line whereas a compiler converts an HLL program into object program in one go and reports all the errors along with their line numbers. Once the program is error free, it can be executed later. The process of translation is called is called as compilation.An assembler converts an assembly language program into object program, identifying any errors along the way.Distinction between Interpreter and Compiler

Interpreter Compiler

Translates the program line by line. Translate the entire program.

Requires less main memory. Requires more main memory.

Each time the program is executed every line is checked for syntax and then converted to equivalent object code directly.

Converts the entire program to machine code, when all the syntax errors are removed and executes the machine code.

Source program and the interpreter are required for execution.

Neither source nor the compiler is required for execution.

Good for fast debugging and at testing stage.

Slow for debugging and testing.

Execution time is more. Execution time is less.

No security of source code. Security of source code.

Computer Programming is the process of planning a sequence of steps for a computer to follow.A Programming language is a set of words, symbols and codes that enables a programmer to communicate a solution-algorithm to the computer.

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Machine or Low level language is the basic language of the computer, representing data as 1’s and 0’s and are closer to hardware.High-level languages are more English-like, closer to human languages. They enable the non-computer professionals, such as executives and managers, who have never studied computer science, to learn and use these languages. E.g. BASIC, C++, Pascal. Assembly language is a low-level programming language that allows a user to write programs using letters and symbols which are more easily remembered.A symbolic program written by a programmer in assembly language is called source program.After the source program has been converted into machine language by an assembler, it is referred to as object program.

Application Software Application software is the set of programs necessary to carry out operations for a specified application. It is required because system software cannot carry out routine jobs performed by the user which application software can easily do. The application software that

a) Manipulates images is known as Graphics Softwareb) Incorporates images, text, sound, computer animation and video sequences is known as

multimedia software.c) Creates professional looking visual aids is called Presentation Graphics Software.d) Handles page layout by combining the functions of a traditional typesetter and a layout

artist, is known as Desktop Publishing Software.e) Assist the computer by performing housekeeping functions like backing up disk or

scanning / cleaning viruses or arranging information etc is known as Utilities.f) Word Processing Package is a package that processes textual matter and creates

organized and flawless documents. Word processors provide following features that enhance their usefulnessProvide variety of fonts and print styles.Information can be saved for later use.Provide the facility of spell-check, dictionary and thesaurus.Offer various formatting styles that enhance the present ability of a document.Offer very useful utility known as mail-merge.

Inter space is a client/server software program that allows multiple users to communicate online with real-time audio, video and text chat in dynamic 3D environments.

CENTRAL PROCESSING UNIT OR SYSTEM UNIT

Processor or Central Processor Unit (CPU) is the control centre for a computer and is contained on a single chip called the microprocessor. A Computer receives information from input devices, stores the information in memory, processes it in the system unit and displays the results as output. CPU is the brain of the computer. It is usually located in a tower- shaped cabinet. The actual processing of data takes place in the CPU. The main components of a CPU are the following:Arithmetic Logic Unit (ALU) performs two types of operations: arithmetic and logical.Arithmetic operations are the fundamental math operations: addition, subtraction, multiplication and division. Logical operations consist of comparisons. That is, two pieces of data are compared to see whether one is equal to (=), less than (<), or greater than (>) the other.

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Control Unit (CU) – It controls and guides the interpretation, flow and manipulation of all data and information. The CU sends control signals until the required operations are done properly by ALU and memory.Registers- The Registers within CPU are special purpose temporary storage locations.The important registers, within CPU are,Programmed counter (PC)-keeps track of next instruction to be executed.Instruction Registrars (IR)-holds instruction to be decoded by the control unit.Memory Address Registrar (MAR)-points to the memory location which the CPU plans to access, either for reading or for writing.Memory Buffer Registrar or Memory Data Registrar (MBR or MDR) - is used for storage data either coming to the CPU or data being transferred by the CPU.Acculmular (ACC) - is used for storing operands, temporary results and results produced by arithmetic logic unit.Motherboard or System board- The system board is the communications medium for the entire computer system. External devices such as keyboard, mouse, monitor, etc could not communicate with the system unit without the system board. The system unit contains a large board that has a number of tiny electronic circuits and other components called the motherboard. The other components of the motherboard are microprocessor, clock, memory- both RAM and ROM in the form of chips, sockets, slots, bus lines and port. Microprocessor is just like any other electronic chip. It is however; more powerful than just any other chip. The microprocessor works on data present on the primary memory. It does the following functions:It has a limited set of on-chip memory locations. These locations are called registers-used to store memory.It can understand a fixed set of basic commands. This set is called the instruction set of the device.It can generate signals that are necessary for controlling external devices. System Clock- A clock chip is used as a timekeeper to enable the components of the computer to work in synchronization. It provides the timing signal in the form of electronic pulses that are used by the components to set a working pace. The clock speed is measured in gigahertz(GHz) or billions of beats per second. The faster the clock speed, the faster the computer can process instructions.Bus Lines (or Bus) called connecting lines provide pathways that support communication among the various electronic components that are either located on system board or attached to system board. A bus is a pathway for bits representing data and instructions. The number of bits that can travel simultaneously down a bus is known as the bus width. The communication between the microprocessor and primary memory takes place through the bus.Ports are inlets and outlets through which input and output devices are connected to system unit.Expansion slots provide expansion capacity for a computer system. Users can insert optional devices known as expansion cards into these slots. For e.g., a modem card plugs into a slot on the system board to provide a connection to the internet.Sockets are used to connect (i.e. provides connection point) the system board to a variety of different types of chips, including microprocessor and memory chips.Chips also called a silicon chip, semiconductor or integrated circuit. Chips consist of tiny circuit boards (which can be smaller than the tip of your finger) etched onto squares of sandlike material silicon.

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Power supply- The system unit draws power from AC (alternating current) mains. The internal components of a computer run on DC (direct current) power to represent data and instructions.There exits an internal power supply components, Switched Mode Power Supply (SMPS), which takes care of the conversion.Exhaust Fan- A fan called the exhaust fan is attached to SMPS. The fan works as long as the computer is switched on to keep the SMPS unit cool.

INPUT DEVICESAn input device is any hardware component or machine used to feed data, programs, commands and user responses into a computer, and converts them into electrical signals (binary form) that can be accepted by the computer. Some of them are following:

Keyboard

Keyboard is a typewriter like device, which contains keys to feed information into the computer.Generally keyboards are available in two models:-

a) Standard keyboards ( 83-84 keys)b) Enhanced keyboards ( 104 or more keys)

The keys of a computer along with their function typewriter keys (a-z), function keys (F1-F12), cursor control keys (,,, ), numeric keys (0-9 ), Special keys (Tab, caps lock, shift, alt, ctrl etc) etc.

SPECAIL KEYS DESCRIPTION

Caps Lock To capitalize letters.

Tab To enter multiple spaces between two words in a document.

Shift To type the special characters above the numeric keys. If you press this key along with a number key, the special character above that number will be typed. E.g. To type “$”, you have to press the shift key and the number key 4.

Space Bar To enter a space.

Home To move the cursor to the beginning of the line.

End To move the cursor to the end of the line.

Insert To insert characters.

Esc To cancel a command.

Backspace To delete the character that is to the left of the cursor.

Delete To erase the character to the left of the cursor.

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Enter To start a new paragraph in a document.

Arrow keys To move the cursor in the top, down, left, and right directions in a document.

Mouse or Mice

Mouse stands for “Mechanical Operated User Serial Engine”. It is connected to the system unit by means of a long chord. It is a rectangular shaped device, with a rubber ball embedded at its lower side and buttons on the topside. Some mouse has a wheel button that can be rotated to scroll through information that is displayed on the monitor. Mouse is used to point at and selects options on the VDU. The mouse pointer usually appears in the shape of an arrow. This is hand held device allows us to control our computer without having to type instructions from the keyboard. Mouse is very easy and faster as compared to the keyboard only in operating system. Three devices similar to mouse are -Track Ball (or Roller Ball) is a pointing device. Essentially, a track ball is a mouse lying on its back. To move the pointer, we rotate the ball with our thumb, or finger, or the palm of our hand.Touch Pad is a small touch-sensitive pad used as a pointing device on some portable computers. By moving a finger or other object on the surface of a pad, we can move the pointer on the display screen.Pointing Stick is located in the middle of the keyboard, to control the pointer by directing the stick with your finger.

When a mouse moves on a flat surface, the cursor on the screen also moves in the direction of a mouse’s movement. There are three kinds of clicks. They are left-click, right-click, double-click.

Left button single click

Point the mouse to an item and click once to select an item.

Left button double click

Point the mouse to an item and click the left button twice, rapidly. This is used to start programs and open files.

Right click Point the mouse and then clicking the right mouse button is used to display the short-cut menu for that item. In most cases, right-clicking on an item or the windows desktop will reveal the properties box for that item.

Shortcut menuA shortcut is an icon that links to a file or folder. A shortcut menu shows the most frequently used commands for a selected item (file, folder or anything else). It is also called context-sensitive menu. The shortcut menu is useful in the sense that all related commands are available at one platform without having to go here and there. Open shortcut menu by right-clicking at a selected item.

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To create a shortcut to a file

Firstly, select the file or folder you want to create the short to. Then drag the file icon through right mouse button to desired location where shortcut is to be placed. The moment you release the right mouse button, a menu appears. On the menu that appears, click create shortcut.Note: A shortcut that appears on the desktop can be copied or moved to another location also.

Drag and drop method

The mouse can be used to drag and drop objects on the screen. Dragging refers to the action of pressing the mouse button on the object and moving the pointer without releasing the mouse button. Dropping refers to the action of releasing the mouse button after the pointer reaches the destination cell.

Joystick

A joystick is a stick set in two crossed grooves and can be moved left or right, forward or backward and controls the movement of a pointer or some other display symbols. It is useful for playing games on computer. You control game actions by varying the pressure, speed and direction of the joystick. A joystick is similar to a trackball as they both allow you to move objects around the screen easily.

Scanner (or Optical Scanner)

A scanner is a device like photocopier, which creates an electronic form of a printed image displayed on the monitor, which can later be manipulated, changed and modified according to the requirements. Printed image is in the form of typed or handwritten texts, graphs, diagrams and photographs. Scanner makes a duplicate copy on paper of the required data or photograph stored in the computer memory.For, e.g. say there is a picture of a bird in a magazine and you want to display it on your computer screen, you can use the scanner to scan the picture available on paper, convert it into bits of information that a computer can understand and save it on the hard disk.There are two basic types of optical scanners:-Flatbed scanner is much like a copy machine. The image to be scanned is placed on a glass surface and the scanner records the image from below.Portable scanner is typically a handheld device that slides across the image, making direct contact. Lawyers and students use portable scanners as a valuable research tool to record information.

Touch Screen is a particular kind of monitor with a clear plastic outer layer. Behind this layer are criss-crossed invisible beams of infrared light. This arrangement enables someone to select actions or commands by touching the screen with a finger. We can use our finger to touch an option on the screen to view information related to that particular option. It is used to receive input as well as give output. Touch screen are often used as input devices in public places such as ATM, Airports, Travel Agencies etc.

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Light Pen

The light pen consists of a photocell mounted in a pen-shaped tube. It utilizes a light- sensitive detector to select objects on a display screen. The light pen is used to draw images on the screen.With the movement of the light pen over the screen, the lines are drawn. It is also useful for programs like CAD (Computer Aided Design) for changing shape, size, location, colours etc. of the screen.

Stylus

A stylus is a pen like device commonly used with table PCs and PDAs. A stylus uses pressure to draw images on a screen. A stylus interacts with the computer through handwriting recognition software. Handwriting recognition software translates handwritten notes into a form that the system unit can process.

Digital Camera

A camera that stores images digitally rather than recording them on film is called digital camera.Once a picture has been taken, it can be downloaded to a computer system, and then manipulated with a graphics program and printed. Digital photos are limited by the amount of memory in the camera. The big advantage of digital cameras is that making photos is both inexpensive and fast because there is no film processing. A digital camera can operate upon without a computer system.

Web Camera

A webcam is essentially a camera that is connected to a computer either directly or wirelessly.It generates digital images that can be accessed by and displayed on web browsers through a server. A web camera can only work with a computer system.

Magnetic Ink Character Recognition (MICR)

This device allows the computer to recognize human readable characters that are printed using a special magnetic ink. MCIR is a direct-entry method used in banks. In a cheque, the branch code, account number, and cheque number are preprinted at the bottom using magnetic ink. The amount of cheque is later entered by a clerk using a machine which prints the amount with magnetic ink.A related technology is the magnetic strip, used on the back of credit cards and debit cards, which allows readers such as ATMs to read account information and facilitate monetary transactions.

Optical Character Recognition (OCR)

This device is used to read characters of a special type font that are printed on conventional paper with conventional ink. An OCR can read the characters printed by computer printers, cash registers, adding machines, typewriters, hand-written documents. OCR is used in departmental stores to read retail price tags by reflecting light on the printed characters. OCRs are used in credit card billing and reading of pin code numbers in large post offices to sort mail geographically.

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Optical Mark Reader (OMR)

In this method, special preprinted forms are designed with boxes which can be marked with a dark pencil or ink. Each box is annotated distinctly so that the user clearly understands what response he is making out of a small number of alternatives. (E.g. answer sheet of a multiple choice question paper where a choice of answer can be reflected by shading the appropriate box.) Such a document is read by a document reader, called optical mark reader (OMR) which transcribes the marks into electrical pulses which are transmitted to the computer. OCRs are best suited for:Various types of surveys where responses can be restricted to one or more out of a few possibilities.Orders forms containing a small choice of items.Time sheets of employees where start and stop times may be marked.

Smart Card Reader

The enhanced version of cards with magnetic strips is called the smart card. The smart card contains a microprocessor that retains certain security and personal data in its memory at all times. The special reader machines that can read information on smart cards are called smart-card readers. Smart cards allow access to crucial information if they are given correct password. The special reader machines that can read information on smart cards are called smart-card readers. Such information is almost impossible to duplicate. Smart card can serve as multi-purpose card e.g., an ATM card, credit card, ID-card, electronic-cash card etc.

Bar Code Reader

A bar code is a pattern of printed bars on various types of products. You can see a bar code printed at the back cover of the book, in supermarkets, bookshops, etc. these are photoelectric scanners that read the bar codes or vertical zebra striped marks, printed on product containers.

Speech Input Devices

Speech or voice input devices convert a person’s speech into digital form. These devices when combined with appropriate software, form voice recognition systems. OUTPUT DEVICES

Output is anything that comes out of a computer. It can be meaningful information and it can be either displayed on the monitor or printed on paper by using a printer in a variety of forms-as binary No’s, or characters, or pictures, or printed pages- in human readable form. The choice of output device depends on the following considerations:Suitability of the application.The speed at which the output is required.Whether a printed version of the output is required.The volume of data, which is output.The cost of the method chosen to the benefits derived.

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Monitor is a television like equipment, which displays the output of a computer. Monitor can be divided into monochrome (black and white), and color (it is displays 16 colours to 1 million different colours).The computer has a screen to display output.This computer screen is called Visual Display Unit (VDU) or monitor.The monitor of the computer resembles a television screen.It can display coloured as well as black and white output.A computer can display data in two modes, text and graphics. In text mode, individual characters are displayed and in graphics mode, images are displayed. Clarity refers to the quality and sharpness of the displayed images.Images are formed on the monitor’s screen by a card called the display adaptor card. Without this card, the PC cannot display output.

Types of monitorCathode-ray tube(CRT) are similar in size and technology to television and are placed directly on the system unit or on the desktop. The primary advantage are low cost and excellent resolution. But CRTs are too bulky to be transported easily and occupy a considerable amount of space on the desktop.Liquid crystal display(LCD) has two basic types. First, passive –matrix or dual-scan monitors create images by scanning the entire screen. This type requires very little power, but the clarity of images is not as sharp. Second, Active-matrix or thin film transistor (TFT)monitors do not scan down the screen; instead, each pixel is independently activated. They can display more colours with better clarity. Active-matrix monitors are more expensive and require more power.

Speakers

The system unit has an audio speaker attached to it. The speaker is connected to the motherboard and produces sound whenever instructed by software programs. The output is in the form of sounds. The sound cards enable the computer, to record sound input from a microphone connected to the computer and stored on a disk.For example, if there is movie playing on the computer, we can hear the characters talk if you have speakers attached to the computer.

Modem

Telephone typically send and receive analog signals, which are continuous electronic waves. Computers send and receive digital signals. To convert the digital signals to analog signals and vice-versa, we need a modem. Modem is short form for Modulation – Demodulation.Modulation is the name of the process of converting from digital to analog.Demodulation is the process of converting from analog to digital. The speed with which modems transmit data is called transfer rate, is typically measured in bits per second (bps).Modems are of four types:Internal modem is fixed within the computer. It consists of a plug – in circuit board inside the system unit. A telephone cable connects the modem to the telephone wall jack.External modem is connected externally by a cable to a computer’s serial port. Another cable connects the modem to telephone wall jack.

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PC Card modem is a credit card –size expansion board that is inserted into portable computers.A telephone cable connects the modem to the telephone wall jack.A wireless modem may be internal, external, or a PC card. Unlike the other modems, it does not use cables. Instead, wireless modems send and receive through the air.

Printer is a device that produces images (No’s, alphabets, graphs etc) on a physical medium such as paper. When we create a document in the computer we can send to the printer for printing its hard copy, which is generally called a printout. Printed information is often called hard copy because the information exists physically and is a more permanent form of output than that presented on a display device. Printers are classified as impact printers and non-impact printers.

Types of Printers

Impact printers In impact printers, the typeface (head or needle) presses against an inked ribbon and makes a mark on the paper i.e. there is physical contact between the paper and the printer head. The most commonly used impact printer is the Dot matrix printer (DMP).

In a dot matrix printer, characters are formed using dots. These printers can print in any language without any additional hardware. They can be made to print in colour by changing ribbons. They can print both text and graphics. They are mainly used to print internal reports and memos needed by organizations.

Plotters are special purpose printers that produce good quality drawings and graphs using ink pens or pencils. A plotter draws images as a series of point-to-point lines. Many applications require a graphical output apart from printed output. For example, pie charts, bar charts and graphs with annotations are useful representation of information. Plotters are widely used by graphic artists, engineers and architects to print out designs, sketches and drawings. There are two types of plotters: drum plotter and flat bed plotter.

Inkjet printer is any printer that fires extremely small droplets of ink onto the surface of paper to create impression of text or image. Such printers have become the defector standard for home computers and low cost printing. They offer good quality at an affordable price.The dots are extremely small (usually between 50 and 60 microns in diameter), so small that they are tinier than the diameter of a human hair (70microns)The dots are positioned very precisely, with resolutions of up to 1440*720 dots per inch (dpi).The dots can have different colours like black, white etc., combined together to create (print) photo-quality images on the same page.The most costly aspect of such printers is replacing the ink cartridges, so most users specify black ink for print jobs.Typically ink-jet printers produce 17 to 19 pages per minute of black-only output and 13 to 15 pages of colour output.

Non-impact printers In non-impact printers, there is no contact between the typeface (head or needle) and the paper while printing i.e. there is no physical contact between the paper and printer head. The most commonly used non-impact printer is the Laser Printer (LP).

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A laser printer uses a beam of light to form images on the paper. Laser printers are used for printing both text and graphics. They are mainly used for publishing newsletters, brochures and presentations. Laser printers are popular due to the high quality of the printout.

A thermal printer uses heat elements to produce images on heat-sensitive paper. Originally these printers were only used in scientific labs to record data. More recently, colour thermal printers have been widely used in professional art and design work to produce very high- quality colour artwork and text.

Photo printers are special-purpose printers designed to print photo-quality images from digital cameras. Most photo printers print 3*5 or 4*6 images on glossy, photo quality paper.

Dot Matrix Printer Laser Printer

A dot matrix printer prints characters using dots.

A laser printer prints characters completely.

The speed is measured in characters per second.

The speed is measured in pages.

Very slow-can be less than 100 characters per minute.

Very fast: 10-20 pages per minute for multiple copies.

Very noisy-can’t be used near a phone.

Almost silent.

Low operating costs. Cannot produce colour copies.

Most expensive printer type to buy specially colour lasers, to repair –lots of complex equipment inside.

Can print on continuous stationary. Using carbonated paper, DMPs can create carbon copies.

Can’t use continuous or multi-part stationary to create carbon copies. Only A4 or A5 paper can be used in most laser printers.

Print quality is too poor to produce important documents for customers or management.

High quality printouts. 600 to 1200 dots per inch.

An Introduction to Windows

Windows is a special type of software known as the operating system, OS in short. It is the rectangular portion of screen that displays an open program or the contents of a folder or disk. Operating system is software that must always be running when the computer is on.Windows provides a Graphical User Interface. A graphical user interface is simple to use because any action that is performed is in the form of buttons clicks or selection of commands.

The Windows Desktop

The large area on the screen that can be seen immediately after Windows gets loaded is called the desktop. Desktop is the workspace on the computer screen, hosting the most widely used applications and features icons. The small pictures on the desktop are called icons. Icon is a

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graphic symbol representing a window element. These small images can represent a file, a folder or a program. The text below each icon is the icon name.Commonly used icons are the following:Application Icons are the graphic renderings of the software package’s logo.Shortcut Icons are little graphics pointing to a particular application, document or folder etc.Document Icons are the active document window, which is a window within an application window, can be minimized to a document icon.Disk – drive Icons graphically represent five disk-drive options: floppy-disk, hard-disk, network, RAM and CD- ROM. ITo open a file, folder or program on the desktop, you need to double-click on its icon. When the mouse is placed over the icon, a text appears identifying its contents. This is called the tool tip.

The Task bar

The narrow blue band at the bottom of the screen is called the task bar. The task bar has the Start menu at the left and the system tray on the right. The date and time are displayed on the system tray. This bar is used to open programs (through start button available on it) and shows information about all open windows. You can easily switch to a different window by clicking its taskbar button. That is, if you are currently working in Microsoft Excel’s window and now you want to switch to Microsoft PowerPoint, which is also active in another window, then, all you need to do is: “click the button representing Microsoft PowerPoint on the taskbar.”

Displaying Toolbars in Taskbar

A tool bar is a bar containing icons for various tools. It is a set of buttons you click to perform common tasks. Right click at the task bar then shortcut menu for taskbar appears. Point to toolbars and then select the toolbar you want to add: an Address bar, a Link bar, a toolbar containing all items on your desktop (Desktop toolbar), or Quick Launch bar. You can also create your own toolbar from any folder. Right-click the background of the taskbar, Point to toolbars, and then click New Toolbar… option. Select a folder from the list. A tool bar containing all items in that folder will be added to your taskbar.Note: You can easily remove a toolbar from the taskbar by right-clicking the taskbar and then clicking the item again to remove the check mark.

Parts of a Window

The parts of a window are the title bar, menu bar the tool bar, the minimize, maximize and close buttons. The top-most blue bar, which contains the name of the window on the left and three buttons on the right, is called the title bar. The bar below the title bar is called the menu bar, there is a tool bar. A tool bar contains shortcuts to items on the menu bar.

To minimize a window, click the Minimise button. The window is minimized to a button on the Taskbar. To restore the window, click its button on the taskbar.To maximize a window, click the maximize button. The window occupies the whole screen. On maximizing a window, the Maximize button changes to the Restore button.Click the Restore button to bring it back to its original size. On restoring the window, the Restore button will be replaced by the Maximize button.

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To close a window, click the Close button.

RESIZING AND MOVING WINDOWS

Resizing a Window – To increase or decrease the size of a window, place the mouse cursor on one of the edges of the window. The cursor changes to a double- headed arrow. Keeping the left mouse button pressed, drag the mouse to resize the window.

Moving a window- Sometimes, a window might hide the icons on the desktop. To move the window, click the title bar and with the left mouse button pressed, drag the window to another place.

Switching between windows- There might be situations where multimedia windows have to be used at the same time. All the windows are displayed as buttons on the taskbar. The button of the active window, that is the window you are currently using, is highlighted on the taskbar. To open some other window, click its button on the taskbar.

WORKING WITH WINDOWS DESKTOP

Arranging Icons on the desktop

Icons can be created and arranged on the desktop. These can be dragged and placed anywhere on the screen. To automatically arrange them,

1. Right-click on the empty space on the desktop.A pop-up menu appears. A menu that appears when you click the right mouse button is called a context-sensitive menu.

2. Choose the Arrange Icons by option from the popup menu. 3. Click the Auto Arrange option. The icons can also be arranged by name, size, type, date etc.

Changing the Desktop

The appearance of a desktop can be changed. To change the appearance of the desktop,1. Right-click on the empty space on the Desktop.2. Click the properties option.3. Click the Desktop tab.4. Select any option from the list box. For e.g., Select Autumn as the background and click

the Apply button.5. Click the OK button to close the dialog box.

The background is also known as the wallpaper.

Changing the Screen Saver

Screen saver is a moving picture or a pattern that appears on the screen when the mouse or the keyboard is not used for a specified period of time. The time can be set using the Wait spin box. To select the screen saver,

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1. Right-click on the empty space on the desktop.2. Click the Properties option.3. Click the Screen Saver tab.4. Select any screen saver from the list.5. Click the Apply button.6. Click the OK button to close the dialog box.

TURNING OFF THE COMPUTER

To turn off the computer,1. Click the start button. The start menu appears.2. Click the Turn off Computer option.3. In the Turn off computer dialog box, click the Turn off option.4. The computer shuts down.

Note: Do not turn off your computer until you see a message telling you that shut down are complete. If you turn off your computer without shutting it down correctly, you risk losing information.

The Start Button

Click the Start button to invoke the Start menu. The menu has two panes.The left side of the menu displays the most frequently used programs. The top left of the menu displays the icons for Internet Explorer and E-mail. The start menu has various menu options such as My Computer, My Documents, My Pictures and My Music And so on.

My Documents: When a new document is created, it is saved in the My Documents folder by default.

My Recent Documents: This option displays the list of files that have been opened recently. You can open a file in My Recent Documents by simply clicking its icon. This option acts as a shortcut to the recently- used files.

My Pictures: By default, picture files are stored in this folder. My Music: By default, music files are stored in this file. My Computer: It is a very important and frequently used option. It helps in accessing the

files and folders in the computer. My Network Places: This option enables you to access your computers on the network.

You can get information about files and folders on other machines. Using this option, you can also share files and folders in your machine so that others can access it from their machines.

The applications in Windows can be started using the Start menu. Click the Start button present in the taskbar. A pop-up menu appears. Select the desired application, which you want to open and press the mouse button on the particular application. The application opens in a window.

CONTROL PANEL

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The control panel contains specialized tools to change the visual settings and the system settings in the operating system. To start control panel.

1. Click the start button.2. Click the control panel option from the start menu.

User Account Option

The user account option in the control panel helps to control the rights and permissions, such as changing passwords and personal settings of a specific user.

Accessibility Option

The accessibility option in the control panel is used for customizing the keyboard, display, mouse functionality. It consists of tasks to change the contrast for the screen elements, such as cursor. And text and configure Windows to work for the users with disabilities. A Magnifier option in the See Also section of Accessibility Options. Using this option portion of the screen can be increased.

Appearance and Themes

The appearance of the desktop can be changed using the Appearance and Themes option in the Control Panel. You can change the background picture, the screen saver and the theme of the desktop. You can also change the appearance and resolution of the computer.To change the theme of the desktop,1. Click change the theme task.2. Click the Theme combo box drop down arrow.3. Choose Windows Classic.4. Click the Apply button.5. Click on the OK button.

The settings of the desktop can also be changed using the display the display icon in the pick a control icon section. This section also contains icons for customizing the folders and start menu.The Display option helps in changing the settings of the desktop, such as the background, screensaver and the appearance.The Folder option helps in changing the way the files and the folders are displayed and change file associations.The Taskbar and Start Menu helps in changing the way the start menu and the taskbar is displayed. Date and Time Option

To change date and time on your system, you can follow the steps given below:1. Click date and time under control panel dialog.2. Now date and time properties dialog box opens up.

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3. Under Date, select the item you want to change: To change the month, click the month list, and then click the correct month. To change the year, click the arrows in the year list, or type the correct year. To change the day, click the correct day on the calendar.After the date is changed, Click the Apply button. Click the OK button.

4. Under Time, select the item you want to change:To change the hour, select the hour, and then click the arrows to increase or decrease the value.To change the minutes, select the minutes, and then click the arrows to increase or decrease the value.To change the seconds, select the seconds, and then click the arrows to increase or decrease the value.To change the AM/PM indicator, select it, and then click the arrows.

Sounds and Audio Devices

This option allows to customize the sound system and also to configure settings for the audio and recording devices. Its task is to change the system volume, sound scheme and speaker settings.Adjust the system volume helps in increasing or decreasing the volume associated with the system.Change the sound scheme helps to change the sound settings that are applied to events in windows.Change the speaker settings helps to change the settings of individual speakers.

Speech

The speech icon allows changing the settings for speech recognition and text to speech conversation. Speech recognition is the ability of Windows XP to convert spoken words to written text.

Keyboard

The keyboard icon has three options to be configured.Speed- Panel enables you to set the repeat rate, repeat delay and cursor blink rate.Language- You can add or remove language definitions from your computer from this panel.General- This panel is where you define the keyboard brand or type.

Changing Mouse Settings

To change various mouse settings or properties, you need to click at Mouse under Control Panel.This will open up Mouse Properties dialog box, wherefrom you can do many things such as:Reversing mouse buttons i.e. make right button work as left button and vice-versa (useful for left-handed people),

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Changing double click speed,Selecting different mouse pointers,Changing mouse speed and pointer trail etc.

Regional Settings

The number, currency, time, and date settings vary from region to region. You can change these settings as per your requirements through Regional and language options under control pane. To do this:Click Regional and Language options under control panel.The Regional and Language options dialog box opens up.On the Regional Options tab, click the name of the region whose number, currency, time, and date format you want to use.Number- You can alter the way numbers appear on your system from this screen.Currency- Use this panel to display and print numbers that represent currency in your region.Time- This panel is where you set the way Windows displays the time.Date- Just like the Time setting screen, this is where you alter the way Windows displays the date.Click at Customize button to set up regional characteristics for Number, Currency, Time, and Date formats.

Add or Remove Programs Option

This option is used to add or remove an application or window components in the control panel.In the control panel, click on Add or Remove programs. You will see Add or Remove Programs Properties dialog box appear on your screen.To remove a program, select it from the list and click change or remove programs to remove it.To add/install new software, click at Add New Programs and than on CD or Floppy button.Follow instructions as they appear on your screen and you will get the desired software installed on your screen.

Add New Hardware

Once you click at Add Hardware in the control panel, the wizard for adding new hardware gets started. This wizard automatically detects and guides you through the process of adding a new piece of hardware to your computer. Make sure you have connected your hardware or installed its components in your computer before running the wizard.To install new Plug and Play hardware, we use this wizard. The plug and play architecture consists of three components:Plug and Play BIOS: This detects and configures Plug and Play cards as part of the POST process.Plug and Play hardware devices: The ESCD data structure holds the current configuration of all devices in the system in some form of non- volatile storage.Plug and Play operating system: The Windows operating system is Plug and Play compatible. It provides the Configuration manager to integrate the automatic hardware configuration process.

Printer and other Hardware

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Using the printer and other hardware option in the control panel, the settings of games control, keyboard, phone and modem, scanner and camera can also be changed. Installed printers and also add a printer to the computer options can be viewed.The Game Controller option helps in changing the settings of the game controller hardware.The Printer and Faxes option helps in changing the display printers that are installed in the machine and also add and remove printers. Using this option, a fax machine can also be added to the system.The Scanner and Camera option helps in adding, removing and changing the scanner and camera settings.

Performance and Maintenance Option

The Performance and Maintenance Option allows to increase space on the hard disk perform frequent checks on the computer and configure settings to save power.The pick a Control Panel icon section contains icons to configure energy-settings and perform administrative settings in the computer.The Administrative Tools option helps in changing the administrative settings in the computer.The Power Option helps in changing the energy saving settings in the computer.The Scheduled Tasks Option helps in running the computer task automatically.The System Option helps to change the hardware settings and also to see the information about the system.

Network and Internet Connections

This option in the control panel consists of tasks to change the settings of the internet, connect to the workplace network from home and create a small office or home network. Icons displayed in the pick a control panel icon section are used for configuring the display and connection settings of the internet and also to connect your computer to other networks and the Internet.

Run Command

The Run option enables you to open a program, folder or a website. Type the name of the program, folder or a website in the Open combo box. To select the location/path or name of desired program/file/folder/web page, click Browse button. Click OK button to run it.For example, to access the calculator, you can type calc in the Open combo box and click the OK button.

DATA ORGANISATION

Just imagine how it would be if we were to search for a book in a library that has no racks. We would never be able to get the books we require. That is why we need to organize our data.Data is defined as the input that is given to a computer. When data is processed into a more useful form, it is known as information. Information is stored in the form of files.File is a computerized document that contains information like Text, Graphics and Numeric data stored on a disk. (Document is a file you create when you save your work in a program.)

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A file name has two parts, the primary name and the extension, also called the secondary name. The primary name is used to identify the file. The extension is used to identify which application has been used to create the file. Example: Text. Doc, here text is the primary part and doc is the extension. A dot is used to separate the primary name and extension. Doc is the extension for Microsoft word files.

Types of Files in Computer’s Storage Media

Text Files: A file containing information in the form of text is called a text file. Textual information can be in the form of letter.

Data File: Data files contain information in binary form. Graphics File: Graphic files contain information in the form of pictures, videos, sketches

and other forms of visual information.

A computer uses drives to store information and each drive is identified by its name, which is called the drive name. The floppy drive is usually referred to as A: and the hard drive is usually referred to as C:

Folder is like a container or file drawer where you can store programs, files and also other folders, pertaining to a particular topic, together in a common location. You use folders to organize files into distinct groups in the same way the drawers and folders inside a file cabinet are used to organize information. MY COMPUTER

My computer is used for accessing information from different drives in the system. In the My Computer window, there are two panes. The left pane has The Explorer bar and the right pane is the working area where you can access your computer.The My Computer window has a menu bar, tool bar, Explorer window and the work area. The work area has icons representing the drives in the system.When you select an icon, the information about that icon appears under the Details section on the left. To view the contents of a drive, double- click its icon. The contents of the drive will be displayed.

WINDOWS EXPLORER

The windows explorer is a feature of windows operating system that can be used to view the contents of a computer and network drives in a hierarchical structure. Instead of opening drives and folders in separate windows, windows explorer lets one browse through them in a single window.To start explorer,

1. Click the start menu.2. Choose the All Programs option in the start menu.3. Choose the accessories option.4. Click the windows explore option in the submenu.

Alternatively, Hold down the start button and press E the key. OR

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Open My Computer and click on the folders button at the top of the My Computer environment.The windows explorer window has a menu bar, tool bar, address bar and two panes.The left pane is called the folder pane. It contains the list of drives and folders on the computer.The right pane is the working area. It displays the contents of a selected folder.

Note: In Windows Explorer, to show or hide folders on the left side of the window, click the plus or minus sign beside the folder.

Use Explorer to view files and folders

To view a folder or a file, then double-click that particular file or folder or right-click the file or folder and the click the open option in the popup menu. When a folder has a subfolder in it, a ‘+’ mark is shown by the side of the folder name. When you click the +mark, it changes to ‘–‘ sign and the subfolders are displayed. When you click the ‘-‘ sign, the parent folder alone is shown and the ‘-‘ changes to ‘+’.

CREATING FOLDERS

Creating a Folder on the Desktop

To create a new folder on the desktop,1. Right click on the empty space on the desktop.2. Click the New option.3. Click the Folder option on the popup menu.

By default, a new folder is named as New Folder. You can change the name to any other name.

Creating a folder in the C Drive

The procedure for creating a folder is same in My Computer and Windows Explorer.To create a folder in the C drive.

1. Double-click the icon for the C drive.2. Click the file menu.3. Choose the new option.4. Click the folder option.Alternatively,1. Double-click the icon for C drive. The C drive window appears.2. Right-click on the empty space in the window.3. Choose the new option.4. Click the folder option.

To create a folder in an existing folder,1. Double-click the icon for the folder.2. Right-click on the empty space.3. Choose the new option.4. Click the folder option.

Say, you create a new folder called Tennis in the Games folder. In this case, the Games folder is called the parent folder and the Tennis folder is called the subfolder.

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CREATING FILES

Creating a file on the Desktop

To create a word file on the desktop,1. Right click on any empty space on the desktop.2. Click the New option from the popup menu that appears.3. Click the Microsoft Word Document option.

By default, the file is named as New Microsoft Word Document. You can change the name.

Creating a file in a folder

The procedure for creating a folder is same in My Computer and Windows Explorer.To create a file in a folder,

1. Double-click the folder to open it.2. Right-click on the empty space in the folder window.3. Create the new file by using the same procedure mentioned above.

FILE OPERATIONS

Files and folders can be copied, moved, deleted or renamed. For this you need to select files that are to be copied, moved or deleted. Selecting a file or a folder is simple, as you have to click that particular folder or file. The folder or file gets highlighted.

Renaming files and folders

A file or folder can be renamed immediately after it is created or later.To rename a file,1. Select the file.2. Click the Rename option in the file menu.Alternatively,

1. Select the file.2. Right- click the file.3. Click the Rename option in the popup menu.

You can also select the file and press the F2 key to change the name.The name of the file or folder is highlighted. Type the new name and press the Enter key.

Rename a file or folder through shortcut menu

1. In a window, select the file or folder you want to rename.2. Right clicks to bring the shortcut menu for selected file.3. Select Rename from the shortcut menu.4. Type a new name, and then press Enter.

Copying files and folders

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To copy a file or a folder to another folder,1. Select the file or folder.2. Click the Edit menu.3. Click the copy option.

Alternatively, you can right-click the file or folder, click the copy option from the shortcut menu or press the Ctrl and C keys simultaneously.

1. Select the folder where you have to paste the file.2. Click the Edit menu.3. Click the paste option.

Alternatively, you can right-click the file or folder, click the Paste option from the shortcut menu or press the Ctrl and V keys simultaneously.

Copy a file to a Floppy Disk

6. Double-click My Computer. Find the file or folder you want to copy, and then click it.7. On the File menu, point to Send To, and then click the drive where you want to copy the file or

folder.

Moving files and folders

To move a file or a folder completely from one folder to another,1. Select the file.2. Click the Edit menu.3. Click the cut option.

Alternatively, you can right-click the file or folder, select the Cut option from the shortcut menu or press the Ctrl and X keys simultaneously.

4. Select the folder where you have to paste the file.5. Click the Edit menu.6. Click the paste option.

If multiple files have to be copied or moved, it can be done using the Shift key or the Ctrl Key.When you want to select consecutives files and folders, click the first item, hold down the <shift> key and click the last item. When you want to select files that are not consecutive, hold down the <Ctrl> key and click each item. To select all files and folders in the window, choose Edit, Select All.

Searching Files and Folders

To search files and folders,1. Click the search option in the start menu.2. Click the ‘All files and folders’ option.3. Specify the name of the file or the folder that has to be searched.4. Specify the folder in which the search has to be happen.

The results are displayed in the right pane. You can also access the search option by pressing the Ctrl and E keys simultaneously.

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Deleting a file or folder

To delete a file or folder,1. Select the file or folder.2. Press the Delete key.

Windows asks for confirmation before deleting a file or folder. Click Yes to delete the file or folder. Click No to cancel the operation.Alternatively, you can right-click the file or folder and select the delete option in the popup menu.

RECYCLE BIN

Recycle Bin is the place that holds the deleted files you no longer need temporarily but are inaccessible. If one wants to undelete a file, then it may be restored from recycle bin. However, if items are deleted from the recycle bin itself, then all of its items in it are permanently deleted and cannot be restored later.

Restoring from the Recycle Bin

To restore a file that is in the Recycle Bin.1. Select the Recycle Bin in the left side pane of the Explorer.2. Select the file that you are planning to restore in the right side pane.3. From the file menu, select Restore.

Emptying the Recycle Bin

To empty the Recycle Bin.1. Select the Recycle Bin in the left side pane of the Explorer.2. From the file menu, select empty the Recycle Bin.3. Windows will ask you to confirm your choice.

Note: Files that have been placed in the recycle bin continue to effectively take up space on your hard drive until you empty the bin. The files or folders removed from a floppy disk (A: or B: drive), or from the DOS command prompt are deleted permanently, it does not go into the Recycle Bin.

PAINT

You can use Paint to create, edit and view pictures. You can use Cut, Copy and Paste techniques to add paint picture into WordPad document you have created or use it as your desktop background. You can create business graphics, company logos, illustrations, maps, cartoons, etc. You can even use Paint to view and edit scanned photos.

To start paint.8. Click at start, then point to All Programs, then to Accessories, and then click at Paint.9. Paint windows open where you can create, edit or view pictures.

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Working in painting Tools

The paint window is made of following tool bars

1. Title bar- The topmost portion of the paint window is termed as title bar. These bars usually display the program name and name of the file we are correctly working in.

2. Menu bar- The menu bar displays a number of options like file, edit, view, image, colour and help. We can select any option of our choice by moving the mouse pointer over it and then click.

3. Work area- The work area section covers a major part of the paint window. The scroll buttons are horizontal and vertical is also available in down and left side of the work area.

4. Colours box- The colour box is present at the bottom of the paint window. It includes various colours.

5. Toolbox- On the left side of the work area we will notice the toolbox. It consists of various tools. These tools help we create drawing as follows:

Tool Name What it does Free-from selected tool Selects irregularly shaped cutouts.Select tool Selects square or rectangular cutouts.Eraser Converts all colours to the currently selected background colour.Fill with colour tool Fills enclosed areas with currently selected foreground colour.Eyedropper tool “Picks up” a colour on your painting that you want to use

somewhere else. The colour you click becomes the foreground colour.

Magnifier Lets you zoom in to any part of your painting to view or edit the pixels (dots) that make up the painting.

Pencil Works just like a pencil. You can adjust the width of the point.Brush “Paints” in a freehand style. Airbrush Sprays a dot pattern of the currently selected foreground colour.

You can adjust the spray width.Text Let’s you type text for captions and titles.Line Draws straight lines at a variety of angles.Curve Lets you create curved shapes. This is a freehand painting tool.Rectangle Paints square or rectangular shapes.Polygon Creates irregularly shaped triangles, boxes and other multisided

objects. Ellipse Creates circles and ellipses.Rounded rectangle Creates squares and rectangles with rounded corners.

CLOPBOARD

The Clipboard is a special file or memory area where data is temporary stored before being copied or moved to another place. For e.g. you can copy an address from one letter to another and thereby avoid retyping it. When you cut or copy information from an application, it is placed onto the clipboard and remains there until you clear the clipboard or until you cut or copy another piece of

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information. Copy command, stores the data on the clipboard but does not remove the original. Cut command removes data and places it on the clipboard. In either case, you use the paste command to copy the contents of the clipboard back into your document. This fact has two important consequences:

1. You must be careful not to erase valuable data that has been placed in the clipboard or you will lose it.2. You can Paste data from the clipboard as many times as you like (until you choose cut or copy again).

Note: The clipboard generally stores only one set of data at a time, although the set of data can be almost any size of length. The contents of the clipboard are cleared each time you select a new set of data and choose either the cut or copy commands again. However, in word 2000, you can have as many as 12 sets of data simultaneously stored in clip board.

The office clipboardIs in addition to the standard windows clipboard.Integrates all office applications.Holds multiple items.Can hold a maximum of 24 items.

To open the clipboard task pane.

1. Click the Edit menu.2. Click the Office clipboard option.

The various buttons on the clipboard and the way you can use them is given below:Paste All: items from the office clipboard.Click All: items from the office clipboard.Paste: a single item.Delete: a single item from the office clipboard.

ENTERTAINMENT IN WINDOWS XP

Windows XP Provide Entertainment Package to the user to facilitate entertainment in the following ways:

Using CD player

You can use CD player to play audio compact disc on a CD-ROM drive connected to your computer. To listen to a CD, you can use head-phones that are plugged into the CD-ROM.If you have a sound card installed, you can listen to a CD over your speaker system.To start a CD player, insert the audio CD in CD Drive and choose Play option.Note: Computer must have sound card and speakers, then only, you can play your music CD’s.

Using Sound Recorder

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You can use Sound Recorder to record, play, and edit sound files. To use Sound Recorder, you must have sound card and speakers installed on your computer. If you want to record live sound, you also need a microphone.To start sound recorder,Click Start, point to All Programs. Then point to Accessories, and then to Entertainment.Now click at Sound Recorder.

Using Media Player

You can use Media Player to play audio, video, or animation files and to control the settings for multimedia hardware devices. To hear sound when you can use Media Player, you must have a sound card.To start media Player,Click Start, point to All Programs. Then point to Accessories, and then to Entertainment.Now click at Windows Media Player.

Using Volume Control

If you have a sound card, you can use Volume Control to adjust the volume and speaker balance when you play audio files.To start volume control,Click Start, point to All Programs. Then point to Accessories, and then to Entertainment.Now click at Volume Control.Now from the Volume Control dialog box, you can control volume as desired.

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