Web Programming CSC 242 Professor John Carelli Kutztown
Web Programming CSC 242 Professor John Carelli Kutztown University Computer Science Department
Introduction to the Web • ARPANET • Beginning late 1960’s • Included about a dozen ARPA sponsored Universities • ARPA: Advanced Research Projects Agency (US Defense Dept. ) • Goal was to provide a network of interconnected computers • Main intention was to provide access to remote computers to facilitate research • Operating at 56 Kbaud (56 k bits/second)! • Conventional telephone communication at the time was 110 b/s • Unexpected consequence – email (electronic mail)! Professor John Carelli Kutztown University Computer Science Department
Network communication • Packet Switching • • Divide message into discrete “packets” Send then independently Reassemble on the receiving end Allowed for simultaneous transmissions by multiple users • No central control • “nodes” behave independently • Network can expand/contract as needed Professor John Carelli Kutztown University Computer Science Department
Transmission Protocols • TCP (Transmission Control Protocol) • Developed for original ARPANET • Ensured messages were properly routed between sender and receiver within the network • IP (Internet Protocol) • more networks developed • IP invented to handle communication between networks • Combination is known as TCP/IP • Allows for a “network of networks” Professor John Carelli Kutztown University Computer Science Department
Network Expansion Initial network use limited • Universities and research institutions • Later, it was expanded to military use Eventually, the government opened it up to commercial use • Initially - resentment in academic community • But, it led to substantial investment, competition, and expansion by businesses • Increase in “bandwidth” Professor John Carelli Kutztown University Computer Science Department
World Wide Web • Two inventions provided standardization for information sharing • Both in content formatting and transmission • Developed by Tim Berners-Lee of CERN (European Nuclear Research Organization) • HTML • Hyper. Text Markup Language • Enables hyperlinked text documents • HTTP • Hyper. Text Transfer Protocol • Communication protocol for sending info across the web • Mosaic (1993) • Web-browser led to explosive growth of web use • developed by University of Illinois - Marc Andressen (later developed Netscape) • Today: Firefox (Netscape), Chrome, IE/Edge, Safari, … Professor John Carelli Kutztown University Computer Science Department
Web Technology • Web is client/server technology • Client (web browser) • requests resources from web servers • Resource – any object retrieved from a web server, such as an HTML document, image, video, audio, database information, etc. • Web servers • Service the request • Use specialized software (apache, IIS) Professor John Carelli Kutztown University Computer Science Department
Hyperlinks Communication between a client browser and a Web server • Browser renders (displays) an HTML webpage • HTML webpages can have embedded “hyperlinks” • Clicking on the hyperlink loads a resource (web page, image, . . . ) • a request for the resource is sent to the server • server sends back the requested item from Internet and the World Wide Web - Deitel Professor John Carelli Kutztown University Computer Science Department
URI’s and URL’s • URI: Universal Resource Identifier • unique identifier for a resource on the Internet • URL: Universal Resource Locator • a URI that begins with http: // • uses Hyper. Text Transfer Protocol to find the resource http: //www. wikipedia. org/wiki/HTML • http: //www. wikipedia. org is the hostname • gets translated into a unique numerical IP (Internet Protocol) address (91. 198. 174. 192) • A Domain Name System (DNS) server maintains a list of hostnames and addresses • wiki/HTML • specifies the targeted resource on the web server Professor John Carelli Kutztown University Computer Science Department
World Wide Web Consortium (W 3 C) • Founded by Time Berners-Lee in 1994 • Developed nonproprietary, interoperable technologies for the WWW • Q: What is meant by nonproprietary? ? • Q: What is meant by interoperable? ? ? • Primary goal – make the web universally accessible • Also a standardization organization • Web technologies standardized by the W 3 C are called Recommendations • Some recommendations include HTML, CSS and XML • www. w 3. org Professor John Carelli Kutztown University Computer Science Department
Web 2. 0 • Term coined in 2003 by Dale Dougherty of O’Reilly Media • Refers to a shift in web usage towards more collaborative, community-based sites and usage • Prior usage was primarily information dissemination from businesses and other providers (Web 1. 0) • Social networking sites, blogs, wikis, etc. • Facebook, Wikipedia, You. Tube, Ebay, … • Involves the user – they create, organize, share, critique, update, etc. the content • The future: Semantic Web • Instead of just sending and reading data on the web, obtain meaning from the data (semantics) Professor John Carelli Kutztown University Computer Science Department
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