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Internet is a vast network of computers that connects many of the world's businesses, institutions, and individuals.  The Internet, which means interconnected network of networks, links tens of thousands of smaller computer networks.  It enables computer users throughout the world to send and receive messages, share information in a variety of forms, and even play computer games with people thousands of miles away.  Computers linked to the Internet range from simple and inexpensive personal computers, often called PC's, to huge mainframe computers used by government institutions, educational institutions, and businesses. 
Computers require special hardware and software to connect to the Internet. Necessary hardware includes a modem, a device that translates a computer's digital information into signals that can be transmitted over telephone lines (see MODEM). Required software includes a communications program that allows the transmission and receipt of messages.
The Internet, often called simply the Net, began as a collection of text-based information.   But the development and rapid growth of a part of the Internet called the World Wide Web (also known as WWW or the Web), transformed the presentation of information on the Net.  In addition to text, the Web allows the use of photographs, moving pictures, and sound to create presentations approaching the visual quality of television and the audio quality of recorded music. 

Uses of the Internet 

The major uses of the Internet include communication, research, publishing, and sales. 
Communication.   Probably the most popular use of the Internet and the Web is electronic mail, also called e-mail.  Virtually every Internet user is assigned an electronic address from which e-mail messages are sent and at which they are received.  The Internet carries hundreds of millions of e-mail messages each day. 
An Internet service provider (ISP) offers local telephone numbers through which an individual, using a computer and modem, can connect to the Internet.  An ISP maintains its customers' e-mail addresses, routes e-mail and requests for Internet-based information to and from its users, and manages high-speed communications lines that speed up Internet sessions.  An on-line service provides a wide range of exclusive content in addition to Internet access. 
Research.   The Internet is like a vast library, containing as much knowledge on every subject as might be held in millions of books.  Information is available in many forms, from files consisting only of text to multimedia files that combine text, photos, animation or video, software programs, and sound.  Internet resources grow larger every day.  
Because of the ease with which information is stored on computers, and the speed with which it can be accessed, the Internet is a popular first stop for many people performing research.   A businessperson might search Internet resources for help in developing sales or product information.  Students can access databases to find material related to homework assignments or courses of study.  Physicians use the Net to compare medical treatments and to review advances in medical science.  Scientists share research data on the Internet. 
Publishing.   Publishers are increasingly using the Internet as a medium for presenting newspapers, magazines, and books.  Because information on the Net is electronic, the publisher is freed from the costs of paper, printing, and distribution.  More importantly, the publisher can update information instantly, making it possible to distribute far more current news than could be provided on paper. 
Sales.   Many businesses use the Internet to carry on commerce.  Retail establishments sell nearly every type of product over the Internet.  Software publishers view the Net as a convenient and inexpensive way to distribute products.  Over the Internet, users can buy new programs, sample programs before purchasing them, or receive upgrades to programs they already own.  Users generally make Internet purchases with credit cards. 
Because tens of millions of people use the Internet every day, advertisers are eager to place messages in frequently visited spots.  Those ads can be electronically linked to an advertiser's own information, which often takes the form of elaborate multimedia files.   In effect, advertisers can invite Internet users to view commercials on their computer.  Additionally, a user can supply the advertiser with his or her e-mail address to get further information or incentives, such as discount coupons. 
The Internet also has important uses within the financial community.  Many banks and stockbrokers offer their customers software to make and track investments from their computer. 
Other uses.  A popular feature of the Net is chat.  Using special software, users can gather in electronic "chat rooms" and send typed messages back and forth, discussing topics of common interest.  The Internet also features many Web-based games with animation, sound effects, and music.  Game players can challenge players in distant countries to tournaments.

How the Internet works 

Computer networks enable computers to communicate and share information and resources.  The simplest networks consist of a user's computer, known as the client, and a resource computer, called the host or server The client makes requests of the host, which, in turn, provides the requested resources, such as information or software. 
The Internet works in much the same way, on a far vaster scale.  To connect to the Net, a user logs on by instructing his or her computer's communication software to call the Internet service provider.  To protect the user's security, this process usually requires a secret password. 
Once connected to the ISP, the user has several options.  For some functions, such as e-mail or text-only resources known as newsgroups, the user's communications software alone may provide access.  Most such software includes simple word processors in which messages can be composed or read. 
For more sophisticated resources, such as the World Wide Web, an additional piece of software known as a browser is used.  With a browser running, a computer user may access millions of sites around the world.  Each site has a separate electronic address, known as a uniform resource locator (URL).  Directories of these addresses are maintained and constantly updated throughout the Internet.  The addresses themselves are organized into various domains (categories), such as educational, commercial, or organizations.  In a URL, the domain type takes the form of a three-letter extension, such as . edu for education and . com for commercial. 
By typing an address, or by clicking the computer mouse's cursor on a picture or word linked electronically to the address, the user transmits a request through the ISP and onto the larger Internet.  When the request arrives at the desired destination, the server computer responds by sending the user its information.  This information often takes the form of a starting page called a home page, which is similar to the table of contents of a book or magazine.  From a home page, the user can search for further information by using links to other pages within the same Web site or to other Web sites. 
Because there are tens of millions of sites, most browsers include systems for bookmarking (recording) the addresses of favorite or frequently visited sites.  Once a site has been bookmarked, the user need simply click on the appropriate bookmark to visit the site again. 
A user need not know in advance the address of the desired information.  Among the most popular features of the Internet and World Wide Web are search engines.  These programs offer users the opportunity to type in key words or phrases related to the information they seek.  The search engine then reviews indexes of information and sites on the Internet and the Web, providing the user with the addresses of sites that most closely match the request.  Because search engine sites are used frequently by millions of people, they are popular spotsfor advertisements. 

The Internet and society 

The Internet has made huge amounts of information accessible to more people than ever before.   The development of the Web in the early 1990's made the Internet relatively easy and fun to use by adding graphics, motion, and sound and by using pictures to represent computer commands.  This accessibility has raised some serious questions. 
Among these questions are doubts about the appropriateness of information.  Not all of the information on the Internet and the Web is accurate, and some is deliberately misleading.   Many schools teach students how to evaluate information derived from the Internet.  
Many parents worry about violent or pornographic material available on the Net.  Criminals may lurk in chat rooms, seeking to arrange face-to-face meetings with unsuspecting victims.  Special programs known as parental control software can help parents restrict access to sites that may be unsuitable for children. 
The Internet also poses security concerns.  Mischievous programmers known as hackers often try to break into large computer systems.  Some hackers damage databases stored in these systems or attempt to steal information or electronic funds.  Others may seek access to credit card numbers and other individual financial information.  Many people are concerned about the security and confidentiality of credit card numbers used to make purchases over the Internet. 
Software itself can become a danger on the Internet.  Programs known as viruses, e-mail bombs, or Trojan horses have been distributed across the Internet and can cause damage to data on systems that receive them.  Many companies produce software designed to protect users against unwanted and damaging viruses. 
Most people believe that the benefits of the Internet far outweigh its dangers.  Although the Internet and the Web have grown quickly, they have revealed only a fraction of their potential as tools for education, research, communication, news, and entertainment.

History of the Internet 

The Internet began to take shape in the late 1960's.  The United States Department of Defense was concerned at the time about the possibility of devastating nuclear warfare.   It began investigating means of linking various computer installations together so that their ability to communicate might withstand a war.  Through its Advanced Research Projects Agency (ARPA), the Defense Department initiated ARPANet, a network of university and military computers. 
The network's operating protocols (rules) laid the groundwork for relatively fast and error-free computer-to-computer communication.  Other networks adopted these protocols, which in turn evolved as new computer and communications technologies became available. 
Throughout the 1970's, the ARPANet grew at a slow but steady pace.  Computers in other countries began to join the network.  Other networks came into existence as well.  These included Unix to Unix Copy (UUCP), which was established to serve users of the UNIX computer programming language, and the User's Network (USENET), a medium for posting text-based articles on a variety of subjects. 
By 1981, just over 200 computers were connected to ARPANet.  The U.S. military then divided the network into two organizations--ARPANet and a purely military network.   During the 1980's, ARPANet was absorbed by NSFNET, a more advanced network developed by the National Science Foundation.  Soon, the collection of networks became known simply as the Internet. 
One of the reasons for the slow growth of the early Internet was the difficulty of using the network.  To access its information, users had to master complex series of programming commands that required either memorization or frequent reference to special manuals. 
The Internet's breakthrough to mass popularity occurred in 1991 with the arrival of the World Wide Web.  The Web was developed by Tim Berners-Lee, a British computer scientist at the European Center for Nuclear Research (CERN).  This development opened the Internet to multimedia. 
In addition, the programming language that the Web used, called HyperText Markup Language (HTML), made it far easier to link information from computers throughout the world.   This development effectively created an interactive index that enabled users to jump easily from the resources of one computer to another, effortlessly following an information trail around the world. 
The arrival of browsers in 1993 further simplified use of the Web and the Internet, and brought about staggering growth in the Internet.  Today, there are tens of millions of computer users accessing the Net and the Web daily.  As the Internet incorporates new technologies that add such features as spoken-word commands, instantaneous translation, and increased availability of historical and archival material, it will continue its rapid growth. 
 Glossary of Internet terms
Bulletin board is an electronic message center. Most bulletin boards serve specific interest groups. They allow users to read messages left by others and to leave their own as well.
Chat room is a location on the Internet where users can discuss topics of common interest by sending typed messages back and forth. The messages appear to other users as soon as they are typed.
Client is a user's computer.
Cookie is a piece of data placed on a client's hard drive by a server. It can be used for a variety of purposes. One such purpose would be to store a name and password so that a user would not have to enter this information every time he or she returned to the same Web site.
Download is to receive data or software over the Internet and store it so that it may be used later.
E-mail , or electronic mail, is a way of sending a message over the Internet to another specific user or group of users.
Firewall is a combination of hardware and software that prevents a visitor to an organization's Web site from gaining access to other information stored on the organization's computer network, such as corporate records or employee information.
Forum , or newsgroup, is an on-line discussion group in which participants with a common interest can exchange open messages.
Home page is the starting page of a Web site. It generally includes tools and indexes to help visitors navigate through the rest of the site. In many ways, a home page functions as an electronic table of contents.
Hyperlink is a programmed connection from one Web site to another. It usually appears on a Web site as a highlighted or underlined word or phrase. When a user clicks a mouse on the passage, the client connects to the related Web site.
Hypertext markup language , or HTML, is the programming language most commonly used by the World Wide Web.
Hypertext transfer protocol , or HTTP, is the set of rules governing the transfer of files between a server and a client. HTTP electronically oversees the connection of clients to Web sites.
Internet service provider is a business that provides a client with the means to connect to the Internet and maintains exchanges of information between clients and servers.
Modem is a device that converts a computer's digital information to signals that can be transmitted over telephone lines. It also converts signals it receives back to digital information.
Net is a common abbreviation for Internet.
Network is a communication system that links two or more computers.
On-line service is a business that provides Internet access plus a wide range of exclusive content and features, such as chat rooms, games, and news reports.
Search engine is a program that allows a user to locate information on the Internet by typing in key words or phrases. The search engine then returns addresses of Web sites that most closely match the request.
Server , or host, is a computer that provides requested resources, such as information or software, to a client via a modem or network connection.
Surfing is the process of visiting a number of Web sites in rapid succession.
Uniform resource locator, or URL, is an electronic address that identifies a Web site.
Web browser , or simply browser, is a piece of software that allows a user to access Web sites.
Web site is a collection of information at a specific address on the World Wide Web.
World Wide Web , or WWW for short, is a part of the Internet that includes text, graphics, video, animation, and sound.


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