Internet

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Internet

  1. 1. Internet
  2. 2. Introduction Of Internet <ul><li>The Internet has been in a state of continuous evolution and sometimes revolution since late 1960’s </li></ul><ul><li>Internet ,are a “Large Computer Network” or “Network Of Networks”,”an instantaneous and global messaging system”. </li></ul>
  3. 3. <ul><li>It has grown into an important infrastructure supporting an increasingly widespread ,multi-disciplinary community. </li></ul><ul><li>This community now consists of students,scientists ,and researchers, large corporations, organizations, government agencies and individual consumers. </li></ul><ul><li>Thus the Internet is a network of thousands of computer networks. </li></ul>
  4. 4. <ul><li>Every network and every computer in these networks exchange information according to certain rules called protocols. </li></ul><ul><li>These different computers and different networks are united with the common thread of two protocols ,I.e. Internet Protocol(IP), and Transmission Control Protocol(TCP). </li></ul>
  5. 5. History Of the Internet <ul><li>The Internet started as a US government project in the year 1960’s called the ARPANET(After the Advanced Research Projects Agency). </li></ul><ul><li>The ARPANET reached universities, research laboratories and some military labs. </li></ul>
  6. 6. <ul><li>In the late 1980’s, the National Science Foundation of U.S . Funded the development of a network.named NSFNET to connect super computers centers in the United States. </li></ul><ul><li>There were more than 10,000 sites in 1987 and more than 100,000 in 1989. </li></ul><ul><li>This large world wide collections of networks and computer systems communicating according to the same protocols has come to be hat is called the Internet. </li></ul>
  7. 7. <ul><li>In 1990 the public network in the U.S. was turned over to NSFNET. </li></ul><ul><li>In 1993 the NSF created the InterNIC to provide Internet services. </li></ul><ul><li>The backbone of the Internet is made up of very high speed communications links owned by companies like At&T,VSNL in India. </li></ul><ul><li>Connections are made by Internet Service Provides(ISP’s) who then tell sell access to individuals or commercial organizations. </li></ul>
  8. 8. Characteristics Of The Internet <ul><li>A Complex Network :- With the simplified definition as a “Network of Networks” that comprises over 150 million computers. </li></ul><ul><li>2 . Disorganized:- The Internet can be cumbersome and confusing ,even for experienced users. </li></ul>
  9. 9. <ul><li>3. A Decentralized System:- Millions of individual networks and over 140 million individual computers connected throughout the world. </li></ul><ul><li>4. Composed of billions files:- Files pertaining(relevant) to thousands of subjects,disciplines(regulations or order) and professions are available in different file format. </li></ul>
  10. 10. <ul><li>5.Widely Used:- More then 147 million people use the internet over 40 million of whom use it daily. </li></ul><ul><li>6.International in Scope:- This global network is accessed by people in approximately 140 countries;people in over 155 countries use internet for Electronic mail purpose. </li></ul>
  11. 11. <ul><li>7.Dynamic:- Changing every minute of every day .On an average , a new network is connected to the Internet every 30 minutes. </li></ul><ul><li>8.Expanding Exponentially:- The Internet is growing at the rate of 12% per month. </li></ul>
  12. 12. Anatomy Of Internet <ul><li>Anatomy refers to the study of structure. </li></ul><ul><li>Internet brings many computers together through the communication media and and protocols. </li></ul><ul><li>It also enable the computers to communicate with one another. </li></ul>
  13. 13. <ul><li>A study of the Internet outlines the following major components of the structure: </li></ul><ul><ul><li>Internet Services </li></ul></ul><ul><ul><li>Elements Of The Internet </li></ul></ul><ul><ul><li>URL </li></ul></ul><ul><ul><li>Internet Protocol </li></ul></ul>
  14. 14. Internet Services <ul><li>The Internet is combinations of many networks and a large number of databases and other services. </li></ul><ul><li>Most of the services can be accessed by using a Web Browser. </li></ul><ul><li>The major services offered on the Internet are: </li></ul>
  15. 15. <ul><li>E-mail:- Electronic Mail </li></ul><ul><li>Mailing lists:- Mailing lists are a group based messaging service. </li></ul><ul><li>FTP:- An Internet service designed for transferring files among computers. </li></ul><ul><li>Newsgroup:- Usenet is public messaging and “Bulletin board” system. </li></ul><ul><li>WWW:-This service features user-friendly publishing and multimedia documents and files. Web pages are created using HTML,JavaScript, and Java. </li></ul>
  16. 16. Elements Of The Internet <ul><li>A simplified hierarchical model of the Internet includes client Pc’s,server computers and networks(composed of clients and servers). </li></ul><ul><li>Client:- These are the computers that request information from servers.I f our personal computer has access to the Internet,it is categorized as a client computer. </li></ul>
  17. 17. <ul><li>Server- These are relatively powerful computers with a full –time Internet connection and can provide data to multiple client computers simultaneously. </li></ul><ul><li>Networks- These are composed of one or more server computers and multiple client PC’s </li></ul><ul><li>Nodes-”Node” is a generic term used to describe a client , server,or networks. </li></ul>
  18. 18. URL <ul><li>Uniform Resource Locators or URL’s , are the unique addresses of Internet resources. </li></ul><ul><li>A URL is divided into 4 parts : </li></ul><ul><li>1. Transfer Protocol </li></ul><ul><li>2. Server Name </li></ul><ul><li>3. Directory Path </li></ul><ul><li>4. File Name </li></ul><ul><li>http/www.yahoo.com/html/appendix.html </li></ul>
  19. 19. Internet Protocol <ul><li>IP is a method by which data is sent from one computer to another over the network . </li></ul><ul><li>Each computer which is connected to the Internet has at least one IP address which uniquely identifies this computer from other computers. </li></ul>
  20. 20. Internet Application
  21. 21. Commerce On the Internet <ul><li>The ability to compose ,send and receive electronic mail is extremely helpful in doing business on the Internet. </li></ul><ul><li>Electronic mail eliminates most of the problems and delays of getting a physical document from one person to another which is essential for doing business. </li></ul>
  22. 22. <ul><li>Another method of doing business on the Internet is setting up a Web Site where we display all our products ,services and any other facilities. </li></ul><ul><li>Presently we can book air ticket , railway reservation and purchases through our credit card over the Internet. </li></ul><ul><li>Online shopping is possible on the Internet these days.By selling items on the Internet ,companies save money on hiring shop workers. </li></ul>
  23. 23. Governance On The Internet <ul><li>Internet is being used for holding meeting with District Magistrates and other people in authority. </li></ul><ul><li>In the field of Education , the results of various examinations are shown on the Web sites of the Universities and Board of education. </li></ul>
  24. 24. <ul><li>Chief Executing Officers these days holds video conference over the Internet for their junior officers.This is a method where they talk face to face using video cameras and Internet Facility.This is called NetMeeting. </li></ul><ul><li>Several Financial and other types of Reports of companies. </li></ul><ul><li>Online Registration </li></ul>
  25. 25. Impact Of Internet On Society <ul><li>Communication </li></ul><ul><li>Knowledge </li></ul><ul><li>Working From Home </li></ul><ul><li>Freedom Of Speech </li></ul><ul><li>Business Exandation </li></ul>
  26. 26. Negative Impact <ul><li>Illegal material shown on Web Sites </li></ul><ul><li>Viruses </li></ul><ul><li>Computerized fund </li></ul><ul><li>Disgusting E-mail </li></ul><ul><li>Crime </li></ul>
  27. 27. Introduction Of Email <ul><li>E-mail is a method of sending messages,voice,video and graphics over digital communication link such as the Internet anywhere in the world at very cost effective rate. </li></ul><ul><li>Technically , email is a type of client/server application that provides a routed,stored message service between any 2 email accounts. </li></ul>
  28. 28. <ul><li>The backbone of an electronic mail system is a communications network that connects remote terminals to a central system or a local area network that interconnects personal computers. </li></ul>
  29. 29. How E-mail works on the Internet? <ul><li>E-mail is the most heavily used feature of the Internet. </li></ul><ul><li>We can use it to send messages to anyone who is connected to the Internet. </li></ul><ul><li>E-mail messages are sent in the same way as most Internet data. </li></ul>
  30. 30. <ul><li>The TCP protocol break your messages into packets,the IP protocols delivers the packets to the proper location, and then TCP reassembles the message on the receiving end so that it can be read. </li></ul><ul><li>We can also attach binary files,such as pictures,videos,sound and executable files to our e-mail messages. </li></ul>
  31. 31. <ul><li>Because the Internet is not able to directly handle binary files in e-mail,the file first must be encoded in one of a variety of encoding schemes. </li></ul>
  32. 32. Structure Of E-mail Message <ul><li>An e-mail message is made up of binary data,usually in the ASCII text format. </li></ul><ul><li>ASCII code describes the characters we see on our computer screen. </li></ul><ul><li>We can attach pictures ,executable programs,sounds,videos, and other binary files to our email message. </li></ul>
  33. 33. <ul><li>There are 5 sections of an E-mail Message: </li></ul><ul><ul><li>E-Mail address </li></ul></ul><ul><ul><li>Header </li></ul></ul><ul><ul><li>Body </li></ul></ul><ul><ul><li>Signature(optional) </li></ul></ul><ul><ul><li>Attachments(optional) </li></ul></ul>
  34. 34. E-Mail Addressing System <ul><li>It is important to understand and follow the email addressing scheme for the Internet to ensure proper delivery of all outgoing messages. </li></ul><ul><li>An email address is composed of 2 separate parts. </li></ul>
  35. 35. <ul><li>1. Our personal identity or account name on that mail server </li></ul><ul><li>2.The domain name of the mail server computer on which we have an e-mail account. </li></ul><ul><li>Example:---- tamanna@rediffmail.com </li></ul>
  36. 36. Header <ul><li>The header of email message is the upper-most section. </li></ul><ul><li>It displays information regarding the status of the messages. </li></ul><ul><li>A header records message information and provides it to the recipients(s) of the message. </li></ul>
  37. 37. <ul><li>Headers are present in both outgoing (sent )and incoming (received)messages. </li></ul><ul><ul><li>To : E-mail address/addresses of primary recipients(). </li></ul></ul><ul><ul><li>Cc: E-mail address/addresses of secondary recipient(s) to whom copy needs to be sent. </li></ul></ul><ul><ul><li>Bcc: E-mail address/addresses of secondary recipient(s) to whom copy needs to be sent but the primary recipient should not know about the dispatch of mail to these addresses. </li></ul></ul><ul><ul><li>From: The originator or the creator of the e-mail. </li></ul></ul><ul><ul><li>Sender : E-mail address of the actual sender. </li></ul></ul>
  38. 38. <ul><li>The header shows information such as: </li></ul><ul><ul><li>Time and date of a message </li></ul></ul><ul><ul><li>Subject of a message </li></ul></ul><ul><ul><li>Whether carbon copies were sent. </li></ul></ul><ul><ul><li>Whether files are attached to the message </li></ul></ul><ul><ul><li>The e-mail address of the sender </li></ul></ul>
  39. 39. Body <ul><li>This body of e-mail message is the primary focus because it contains the actual message. </li></ul><ul><li>Many Internet Service Providers do limit the size of an E-mail message. </li></ul>
  40. 40. <ul><li>Date : Date and Time the message was sent. </li></ul><ul><li>Reply-To: Email address to which replies should be sent. </li></ul><ul><li>Subject:- A summary of the message for the online display. </li></ul>
  41. 41. Attachments <ul><li>E-mail has become all the more attractive to business because now it allows users to attach a file to any e-mail message. </li></ul><ul><li>Any file format-such as word processing documents, spreadsheets, images or video files can be attached to an e-mail message. </li></ul><ul><li>E-mail allows complex data as attachments but not in the body. </li></ul>
  42. 42. <ul><li>E-mail messages cannot contain viruses,but they can still be sent through attachments. </li></ul><ul><li>Therefore, we should scan all email attachments with a virus detection and eradication software program . </li></ul><ul><li>It Is optional. </li></ul>
  43. 43. Signature <ul><li>The signature for an e-mail message is the personal information which automatically appears at the bottom of the outgoing message. </li></ul><ul><li>Use of signature is optional. </li></ul><ul><li>We can provide any signature information we wish. </li></ul>
  44. 44. <ul><li>The purpose of a signature (also called a signature block,signature file)is to provide a message recipient with personal contact information. </li></ul><ul><li>By utilizing the signature feature of the e-mail software , we can avoid typing information for each outgoing message. </li></ul>
  45. 45. <ul><li>Information in a signature block may include the following: </li></ul><ul><ul><li>Full name </li></ul></ul><ul><ul><li>Job title </li></ul></ul><ul><ul><li>Organization name and division </li></ul></ul><ul><ul><li>Phone and fax numbers </li></ul></ul><ul><ul><li>Physical address </li></ul></ul><ul><ul><li>E-mail address </li></ul></ul><ul><ul><li>Web site address(URL) </li></ul></ul>
  46. 47. World Wide Web
  47. 48. What is w.w.w <ul><li>The world wide web or the “web”,is an internet –based global information system that makes multimedia information available from over 4 million computers around the world. </li></ul><ul><li>The web offers video, interactive multimedia and live audio, in addition to more basic data types, such as text documents and photographs. </li></ul>
  48. 49. Evolution Of World Wide Web <ul><li>World Wide Web (www)is a huge collection of hypertext pages on the internet. </li></ul><ul><li>The concept of WWW was developed in Switzerland at the European particle Research Center in the year 1989. </li></ul><ul><li>In the year 1993, the first Graphical interface software package called Mosaic was released. </li></ul>
  49. 50. <ul><li>The Mosaic became so popular later . </li></ul><ul><li>In the year 1994, CERN and MIT of USA signed an agreement setting up the world wide web consortium, an organization devoted to further developing the web, standardizing protocols,and interoperability between sites. </li></ul><ul><li>In the first year after Mosaic was released, the number of WWW servers grew fron 100 to 7000. </li></ul>
  50. 51. <ul><li>The growth will be exponential in the years to come and will probably be the force driving the technology and use of the Internet into every walk of life of human being. </li></ul><ul><li>To access the Web server , we use client software called a Browser program. </li></ul>
  51. 52. Basic Features <ul><li>The web is one of the most flexible and exciting tools for surfing of the Internet. </li></ul><ul><li>The www made it possible for a site to set up a number of pages of information containing text, picture , sound, and even video with embedded links to other pages. </li></ul><ul><li>By clicking on a link , the user is moved to the page pointed to by that link. </li></ul>
  52. 53. 1.Hypertext Information System <ul><li>The idea behind hypertext is that instead of reading text in a rigid linear structure , you can skip easily from one point to another. </li></ul><ul><li>The World Wide Web provides more information that you could ever digest in a lifetime, linked together in various ways, available for you to browse whenever you want. </li></ul>
  53. 54. 2. Graphical and Easy to Navigate <ul><li>One of the best features of the Web is its ability to display both text and graphics in full color on the same page. </li></ul><ul><li>Before the Web, using the Internet involved simple text-only connections or complicated interfaces or encoding to view graphic. </li></ul><ul><li>Newer web browsers include capabilities for multimedia and embedded applications. </li></ul>
  54. 55. 3.Cross-Platform <ul><li>If you can access the Internet , you can access the World Wide Web regardless of whether you are running on a low – end PC or an expensive graphics workstation. </li></ul><ul><li>Cross-platform means that you can access Web information equally well from any computer hardware running any operating system using any display. </li></ul>
  55. 56. 4. The Web is Distributed <ul><li>The web is successful in providing so much information because that information is distributed globally across thousands of Web sites, each of which contributes the space for the information it publishes. </li></ul><ul><li>You as a consumer of that information, go site to view the information . </li></ul>
  56. 57. 5.The Web is Dynamic <ul><li>Because information on the web is contained on the site that published it, the people who published it in the first place can update it at any time that’s why it is dynamic in nature. </li></ul>
  57. 58. 6.Accessing Many Forms of Internet Information <ul><li>There are dozens of different ways of getting the information on the Net namely FTP, Gopher, Usenet news, WAIS databases, Telnet and E-mail. </li></ul><ul><li>The web browsers namely Internet explorer Netscape Navigator have changed all this . </li></ul><ul><li>Although the Website has its own information system,with its own Internet protocol(HTTP). </li></ul><ul><li>Web browsers can read files from other Internet services and we can create links to information on web pages. </li></ul>
  58. 59. 7.Web is Interactive <ul><li>Interactively is the ability to “Talk Back” to the web server. </li></ul><ul><li>It means the act of selecting a link and jumping to another Web page to go somewhere else on the Web. </li></ul><ul><li>In addition to this simply interactivity , the Web also enables you to communicate with the publisher of the pages you are suffering. </li></ul>
  59. 60. Web Browser <ul><li>A browser is an interface between human and the internet. </li></ul><ul><li>A web browser is a program we use to view pages on and navigate the world wide web. </li></ul><ul><li>It is also known as “Internet navigation Tool”. </li></ul>
  60. 61. Services of Browser <ul><li>A web browser does the following 2 types of services: </li></ul><ul><ul><li>1.It gives a URL address, through we can access information. </li></ul></ul><ul><ul><li>2.It used to communicate with the web server using the HTTP protocol. </li></ul></ul>
  61. 62. <ul><ul><li>3.Web can also manage information contained on FTP and Gopher servers ,in Usenet news postings, in E-mail, and so on , browsers can often communicate with those servers or protocols as well. </li></ul></ul><ul><li>Currently the most popular browsers for the world wide web are Netscape’s Navigator , developed by Netscape Communications Corporation and Internet Explorer developed by Microsoft Corporation. </li></ul>
  62. 63. Popular Web Browsers
  63. 64. Mosaic <ul><li>Mosaic was the first full-color graphical browser and is the instrumental in making the web as popular as it today. </li></ul><ul><li>Mosaic was developed by ncSa. </li></ul><ul><li>ncSA Mosaic is free for personal use and comes in versions for windows,Macintosh,and Unix. </li></ul><ul><li>Each version is called WinMosaic , MacMosaic and XMosaic respectively. </li></ul>
  64. 65. Lynx <ul><li>If the only connection we have to the Internet is through a dial-up text only UNIX account ,we are limited to using text-only browsers such as Lynx. </li></ul><ul><li>We will not be able to view documents in color or view graphics online. </li></ul><ul><li>Lynx runs on systems that lack the ability to display graphics ,viewing web pages using Lynx gives us nothing but the text and the links </li></ul>
  65. 66. Netscape Navigator <ul><li>Netscape Navigator also familiarly known as Netscape is available for windows,Macintosh, and for many versions of UNIX running the x window system. </li></ul><ul><li>It is well supported and provides up-to the minute features including an integrated news and mail reader ,support for java applets , and the ability to handle “plug ins” for more new and interesting features yet to be developed. </li></ul>
  66. 67. Microsoft Internet Explorer <ul><li>Microsoft Internet Explorer usually just called Explorer. </li></ul><ul><li>Explorer just runs on all versions of Windows OS,and Macintosh and it is free downloading from Microsoft web site. </li></ul>
  67. 68. Web Server <ul><li>To make available the services of Web pages , Web sites need host-a computer and server software that runs on the host . </li></ul><ul><li>The host manages the communications protocols and the related software required to create a Web site on the Internet. </li></ul>
  68. 69. <ul><li>The host machine often uses the UNIX, Windows NT, Windows 2000 or Macintosh Operating systems which have the TCP/IP protocols built in. </li></ul><ul><li>The server software resides on the host and serves up the pages and other wise acts on the requests sent from the client browser software. </li></ul>
  69. 70. <ul><li>A Web server is the program that runs on a Web Site and is responsible for replying to web browser requests for files. </li></ul><ul><li>We need web server to publish documents on Web. </li></ul><ul><li>There are different types of server software like web server,database server or network server etc. that perform different types of services for different types of clients. </li></ul>
  70. 71. Functions Performed By Web Server <ul><li>It passes requests to run CGI(Common Gateway Interface) scripts to the CGI applications.These scripts run external mini-programs,such as a database lookup or interactive processing. </li></ul><ul><li>The server software includes configuration files and utilities to secure and manage the Web site in a variety of ways. </li></ul>
  71. 72. Working of Web Server <ul><li>Client (Internet Browser)software sends its request for data to the Host, and the Web server software processes the request . </li></ul><ul><li>If the browser asks for a HTML file,the Web server retrieves the file,attaches a header to the file,and sends it to the browser. </li></ul>
  72. 73. <ul><li>If the browser has asked for specific database information,the Web server will pass a request through CGI to the application,which performs a database lookup. </li></ul><ul><li>The CGI script returns the result to the Web server,which in turn attaches a header to the data and sends it to the browser. </li></ul>
  73. 74. Search Engine <ul><li>A Search Engine is a software that searches through a database of web pages for specific information. </li></ul><ul><li>Web Search is an Information Retrieval problem. </li></ul><ul><li>As compared to searching a database , the search for a document contents is more terrifying since it is not structured. </li></ul>
  74. 75. <ul><li>Documents should be indexed for making search easier and less time consuming. </li></ul><ul><li>The effectiveness of search engine can be measured by two main parameters: </li></ul><ul><ul><li>Indexing </li></ul></ul><ul><ul><li>Term Specificity </li></ul></ul>
  75. 76. Indexing <ul><li>Indexing is the processing of a document representation by assigning content descriptions or terms to the document. </li></ul>
  76. 77. Categories Of search Engines <ul><li>There are many search engines available on the web. </li></ul><ul><li>Most of the search engines provide website reviews and homepage services ,in addition to keyword searches. </li></ul><ul><li>Some popular search engines are: </li></ul>
  77. 78. Yahoo <ul><li>It is a basically a search directory </li></ul><ul><li>It is hierarchically organized with subject catalogue or directory of the web which is browsable and searchable. </li></ul><ul><li>This search engine has 14 categories listed on its homepage. </li></ul><ul><li>Each of these categories is divided into several subcategories. </li></ul>
  78. 79. <ul><li>We can search yahoo in 2 modes: </li></ul><ul><ul><li>Yahoo search page </li></ul></ul><ul><ul><li>Yahoo search options </li></ul></ul><ul><li>Yahoo offers a lot of extra services like free mail accounts, region-specific sites, site reviews, and a customizable news page. </li></ul>
  79. 80. AltaVista <ul><li>This has been created by the research facility of Digital Electronic Corporation(DEC)of USA. </li></ul><ul><li>This search engine has a spider that traverses the Web . </li></ul><ul><li>Alta vista search supports full phrase and case sensitive searches. </li></ul><ul><li>The engine has 2 modes of search types namely, simple and advance search. </li></ul>
  80. 81. <ul><li>In simple search,AltaVista will attempt to find pages that include as many of your search words as possible,and rank those pages highest to lowest in the result. </li></ul><ul><li>In advance search, the page uses the same syntax rules as the basic search, but it adds Boolean operators to make searches more flexible. </li></ul><ul><li>The operators include &(And),| (OR),and !(Not). </li></ul>
  81. 82. HotBot <ul><li>This engine retrieves and indexes Web documents using a robot called Slurp and a parallel network of workstations. </li></ul><ul><li>HotBot offers simple keyword as well as Boolean searches. </li></ul><ul><li>This search engine is most suitable for searching specific words or phrase. </li></ul>
  82. 83. <ul><li>The HotBot search contains a text box for the users to enter their query string, and a list box to choose the appropriate rule , like all words,any words or exact phrase. </li></ul>
  83. 84. WEB Crawler <ul><li>Web Crawler has a powerful search customization and a good selection of site reviews. </li></ul><ul><li>Web Crawler also features a WebRoulette,which suggests randomly selected sites for you to visit. </li></ul><ul><li>It has another option called surf the web backwards,which allows you to enter an url and get a list of all the sites which link directly to it. </li></ul>
  84. 85. Excite <ul><li>It uses a spider and indexer for the full text search of documents. </li></ul><ul><li>The spider retrieves only web and usenet news group documents </li></ul><ul><li>It also includes operators like &(And),| (OR),and !(Not). </li></ul>
  85. 86. InfoSeek <ul><li>It is a popular search engine with a robot that retrieves HTML and PDF documents. </li></ul><ul><li>InfoSeek allows searches in the web ,Usenet groups and Web Frequently asked Questions(FAQ’s). </li></ul>
  86. 87. Other Search Engines <ul><li>There are many other search engines on the Web such as InfoMarket, IndiaInfo.com,All4One and High-ways61.com. </li></ul>
  87. 88. Search Tools <ul><li>The search tools have 2 ways to find specific information: </li></ul><ul><ul><li>Directories </li></ul></ul><ul><ul><li>Spiders </li></ul></ul>
  88. 89. Directories <ul><li>Directories is the arranging method of files. </li></ul><ul><li>The problem with directories , which store knowledge in some structure , is that classification is a labour intensive activity, and there are far more publishers of directories than classifiers on the web. </li></ul><ul><li>And if the information is not reflected by the classification structure , then you are out of luck and this happens very often.s </li></ul>
  89. 90. Spider <ul><li>Spiders explores the Web and helps to find web pages. </li></ul><ul><li>It is also known as robot,crawler, or bot. </li></ul><ul><li>Spiders have the ability to test databases against queries and order the resulting matches. </li></ul><ul><li>s </li></ul>
  90. 91. Hypertext <ul><li>Hypertext is a system of organizing , navigating </li></ul>

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