Chapter 8
Government and Universities over 30 years Who’s connected today?
◦ Individuals◦ Educational institutions◦ Government◦ Research◦ Medical◦ Businesses◦ Everyone!
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
Messages divided into packets
TCP/IP protocol◦ TCP – does the packeting and reassembling of
the message◦ IP – handles the addressing
Research computers from universities Defense contractors Needed technical expertise to work on
Internet
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
Unique address of a web page or file on the Internet
Case-sensitive
http://domain-name.top-level-domain/last-section
Protocol – rules Communication using links
http://domain-name.top-level-domain/last-section
Address of the ISP Domain names are registered Ongoing fee is paid for each domain
name
http://domain-name.top-level-domain/last-section
Represent the purpose of the organization of entity
.com
.gov
.edu
.org
.net
May be a two-letter country code
Directories and file names that specify a particular web page
http://domain-name.top-level-domain/last-section
Computer with a modem or NIC Internet service provider (ISP) Browser Related software
Vehicle to access the Internet Provides
◦ Server computer◦ Software to connect
ISP Members-only services and information Simple interface with clickable topics Parent controls
Used to explore the Internet Dials the ISP Display web pages
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
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
Pull-down menu Buttons
◦ Convenient shortcuts for commonly used functions
◦ Click button rather than locate command from pull-down menu
Software that increases the functionality of a browser◦ Audio-video◦ Image viewing
Download from web sites Install Example
◦ Adobe Acrobat Reader◦ Shockwave
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
Clickable categories in the browser◦ Sports◦ Weather◦ News◦ Technology◦ Comic strips
Enter the URL in the address text box and press <Enter>
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)
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
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
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
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
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
Directories Yahoo! NetGuide
Metasearch Sites MetaCrawler Dogpile
Search Engines AltaVista Excite Google HotBot Infoseek Lycos Northern Light
Add words Enclose words in “quotes” Use Boolean logic Examples
◦ “World Trade Center” ◦ Jordan AND NOT Michael