CSCI-235Micro-Computers in Science

The Internet and World Wide Web

The Internet and World Wide Web: Welcome to Cyberspace 2

The Internet

A network of networks

Began in 1969 as ARPAnet (Advanced Research Projects Agency)

No central authority and thus impossible to state the precise size

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The Internet and Web: What’s the Difference?

The Internet is the physical connection of millions of networks

The Web uses the Internet for its existence

The Web consists of hypertext embedded on Web pages that are hosted on Web sites Began in 1991 at the European Particle Physics

Laboratory (CERN) in Switzerland

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Web Browsers and Servers

Web browsers display a Web document and enable users to link to other Web pages The first browsers were text-only Mosaic was the first graphical browser

Web servers respond to the requests of browsers. They find and send requested resources back to the browser

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Menu Bar File Edit View Favorites Tools Help

Address Bar URL

Toolbar Back Button Forward Button Stop Refresh Home Search Favorites History

Microsoft Internet Explorer

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Status Bar

Menu Bar

Tool Bar

Address Bar

Hyperlink

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Web addresses are an addressing system that identifies where a Web resource is located

The uniform resource locator (URL) is the standard used to identify Web resources

The URL consists of:

URL

Uniform Resource Locator (URL)

http://

Protocol identifies the means of access

www.yahoo.com/

Server contains the domain name of the Web server

help/shop/

Path identifies the

location of the document

shop-01.html

Resource specifies the

filename of the resource

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Search Engines

A program that systematically searches the Web for documents on a specific topic

Uses a key word or words as a query Several search engines are available Each search engine has its own database No search engine is best Uses Boolean (logical) operators Returns “hits” or documents once search has

been submitted

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Search Rules and Techniques

Specify Boolean operatorsAND -- Includes all findings of both key wordsOR -- Looks for only one of the specified key

wordsNOT -- Allows you to exclude certain key words

Use multiple search engines

Read online help about search criteria used for a particular search engine

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http://www.altavista.com/ http://www.msn.com/

http://www.go.com/ http://www.excite.com/

http://www.lycos.com http://www.askjeeves.com/

http://www.webcrawler.com/ http://www.google.com/

http://www.yahoo.com http://www.search.com/

Popular Web Search Engines

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Security and Privacy

Secure transactions Https protocol Encryption

Privacy A cookie is a small file written to your disk each

time you visit a site

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HTML

HTML – HyperText Markup Language: language for all Web documents

HTML Codes - Necessary to format the page