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Published byWilliam Casey Modified over 9 years ago
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Chapter 8
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Government and Universities over 30 years Who’s connected today? ◦ Individuals ◦ Educational institutions ◦ Government ◦ Research ◦ Medical ◦ Businesses ◦ Everyone!
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1969 – US Department of Defense and Rand Corporation Origins ◦ Cold War – fear that a bomb could demolish computing capabilities ◦ Several computers, geographically dispersed, networked together ◦ Plan – if one computer was disabled, others could carry on using alternative communication routes
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Messages divided into packets TCP/IP protocol ◦ TCP – does the packeting and reassembling of the message ◦ IP – handles the addressing
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Research computers from universities Defense contractors Needed technical expertise to work on Internet
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Mid 1990s Estimate over 333 million users worldwide Part of our daily lives Four factors ◦ TCP/IP standard ◦ Ability to link from site to site ◦ Ease of use of browser ◦ Growth of PC and LANs that can connect
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Unique address of a web page or file on the Internet Case-sensitive http://domain-name.top-level-domain/last-section
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Protocol – rules Communication using links http://domain-name.top-level-domain/last-section
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Address of the ISP Domain names are registered Ongoing fee is paid for each domain name http://domain-name.top-level-domain/last-section
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Represent the purpose of the organization of entity.com.gov.edu.org.net May be a two-letter country code
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Directories and file names that specify a particular web page http://domain-name.top-level-domain/last-section
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Computer with a modem or NIC Internet service provider (ISP) Browser Related software
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Vehicle to access the Internet Provides ◦ Server computer ◦ Software to connect
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ISP Members-only services and information Simple interface with clickable topics Parent controls
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Used to explore the Internet Dials the ISP Display web pages
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Browser display window ◦ Displays contents of web page from each Internet site visited ◦ Screen limits how much of the site you can view at a time. The page can be scrolled using the scroll bar to see its entire contents Status line – progress of data being transferred and other messages
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Welcome banner on title bar Browser logo – animation indicates you are in the process of moving to a new site Hot list ◦ Bookmark ◦ Favorites ◦ Store your favorite URLs Browser control panel – menus and buttons
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Pull-down menu Buttons ◦ Convenient shortcuts for commonly used functions ◦ Click button rather than locate command from pull-down menu
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Software that increases the functionality of a browser ◦ Audio-video ◦ Image viewing Download from web sites Install Example ◦ Adobe Acrobat Reader ◦ Shockwave
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Java Write software that is machine independent Programming language Dancing icons Sound clips Flashing messages Banners that scroll Applets – Permits dynamic web pages Display animations Receive input Perform calculations
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Clickable categories in the browser ◦ Sports ◦ Weather ◦ News ◦ Technology ◦ Comic strips Enter the URL in the address text box and press
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User enters a URL User computer sends request to the ISP server ISP server sends request across networks of TCP/IP computers Destination site is reached Content is transmitted back to your computer (process in reverse)
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Search engine User specifies a search request Browser links to Search Engine Request returns matching pages based upon the Search Engine’s database Results presented
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Search Engine builds database ◦ Searchable terms ◦ Related web sites Spider, robot, bot ◦ Follows links across the web ◦ Automatically indexes pages to a database One word All words Pages may be submitted by the owner
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Request same search using different engines yields different results Databases built independently ◦ Size ◦ Content ◦ Search methodology Metasearch – atomically puts the same request to several search engines
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Directory Human involvement Sites organized by content category May concentrate on specific content areas Subjective decisions regarding inclusion and importance Search Engine Spider, robot, or bot automatically builds database Index on a few keywords Index on all words on web page
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Index only a fraction of the Web Approximately 20% to 33% of sites More web pages added daily Solution ◦ Same request to several search engines ◦ Metasearch
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Directories Yahoo! NetGuide Metasearch Sites MetaCrawler Dogpile Search Engines AltaVista Excite Google HotBot Infoseek Lycos Northern Light
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Add words Enclose words in “quotes” Use Boolean logic Examples ◦ “World Trade Center” ◦ Jordan AND NOT Michael
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