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