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CHAPTER 1

CHAPTER 1. Internet & World Wide Web. Topics. A Brief Introduction to the Internet The World Wide Web Web Browsers Web Servers Uniform Resource Locator Tools and Web Programming Languages. Learning Outcomes. At the end of this lesson, students should be able to:

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CHAPTER 1

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  1. CHAPTER 1 Internet & World Wide Web

  2. Topics • A Brief Introduction to the Internet • The World Wide Web • Web Browsers • Web Servers • Uniform Resource Locator • Tools and Web Programming Languages

  3. Learning Outcomes At the end of this lesson, students should be able to: • Understand history and concepts related to Internet and World Wide Web. • Understand a number of tools and web programming languages that are used in web development.

  4. A Brief Introduction to the Internet Origins • ARPAnet - late 1960s and early 1970s. • For ARPA-funded research organizations. • BITnet, CSnet - late 1970s & early 1980s. • Was built for email and file transfer for other institutions.

  5. A Brief Introduction to the Internet • NSFnet - 1986 • Originally for non-DOD funded places. • Initially connected five supercomputer centers. • By 1990, it had replaced ARPAnet for non- military uses. • Soon became the network for all (by 1990). • NSFnet eventually became known as the Internet.

  6. A Brief Introduction to the Internet What the Internet Is • A world-wide network of computer networks. • At the lowest level, since 1982, all connections use TCP/IP. • TCP/IP hides the differences among devices connected to the Internet. • Internet is actually a network of networks rather than a network of computers.

  7. A Brief Introduction to the Internet IP Address • Every node has a unique numeric address. • Form: 32-bit binary number. • Usually written as four 8-bit numbers, separated by periods. • Example: 191.57.126.0 8 bits 8 bits 8 bits 8 bits

  8. A Brief Introduction to the Internet • New standard, IPv6, has 128 bits (1998) • Organizations are assigned groups of IPs for their computers. • Example: A small organization may be assigned 256 IP addresses, such as 191.57.126.0 to 191.57.126.255.

  9. A Brief Introduction to the Internet Domain • Form: host-name.domain-names • First domain is the smallest; last is the largest. • Last domain specifies the type of organization. • Fully qualified domain name - the host name and all of the domain names.

  10. A Brief Introduction to the Internet • Example: www.arwen-undomiel.com/misc/dict.html arwen-undomiel.com is a domain name of above web site. www is the host. • DNS servers - convert fully qualified domain names to IPs.

  11. The World Wide Web Origins • Tim Berners-Lee at CERN proposed the Web in 1989. • Purpose: to allow scientists to have access to many databases of scientific work through their own computers.

  12. The World Wide Web • Hypertext- text with embedded links to text in other documents to allow non-sequential browsing of textual material. • Hypermedia – more than just text – images, sound, etc.

  13. Web Browser • Mosaic - NCSA (Univ. of Illinois), in early 1993. • First to use a GUI, led to explosion of Web use initially for X-Windows, under UNIX, but was ported to other platforms by late 1993. • Browsers are clients - always initiate, servers react (although sometimes servers require responses).

  14. Web Browser • Most requests are for existing documents, using HyperText Transfer Protocol (HTTP). • But some requests are for program execution, with the output being returned as a document. • Example of web browsers: Netscape, Opera, Internet Explorer, Mozilla, Firefox, Google Chrome, Safari.

  15. Web Server • Provide responses to browser requests, either existing documents or dynamically built documents. • Example of web server: Apache, Microsoft Internet Information Server.

  16. Uniform Resource Locator (URL) The Structure of URLs • Taking http://www.mydomain.net/~rdralph/rdralph/ as an example.

  17. Uniform Resource Locator (URL) Common Internet Protocols • There are several protocols used commonly on the Internet to get to a variety of sites which support them. • The protocol which supports the World Wide Web - just one component of the Internet - is http - hypertext transfer protocol.

  18. Uniform Resource Locator (URL) Common Internet Protocols

  19. Uniform Resource Locator (URL) Common Internet Protocols

  20. Uniform Resource Locator (URL) Host Domain Names • Form of host domain names: • The Location name is almost always mnemonic - an abbreviation of the location name or an acronym for it. • A lot of the time the location name is not abbreviated at all.

  21. Uniform Resource Locator (URL) • The domain can tell us what type of site we can expect to be visiting. Common Domain Acronyms

  22. Uniform Resource Locator (URL) • Some sites use a geographical approach in their domains. • The last two positions in the domain of a WWW site outside the US often represents the country. • Universal two-letter country codes are used. For example: my= Malaysia, sa = Saudi Arabia, uk = The United Kingdom, sg = Singapore

  23. Uniform Resource Locator (URL) Paths in URLs • The tilde (~) generally precedes the name of a directory assigned to a person. • In the URL http://metalab.uniten.edu.my/~mia, for example, the mia part indicates an account name associated with the author mia.

  24. Tools and Web Programming Languages HTML • To describe the general form and layout of documents. • An HTML document is a mix of content and controls. • Controls are tags and their attributes.

  25. Tools and Web Programming Languages • Tags often delimit content and specify something about how the content should be arranged in the document. • Attributes provide additional information about the content of a tag.

  26. Tools and Web Programming Languages XML • A meta-markup language. • Used to create a new markup language for a particular purpose or area. • Because the tags are designed for a specific area, they can be meaningful. • No presentation details. • A simple and universal way of representing data of any textual kind.

  27. Tools and Web Programming Languages JavaScript • A client-side HTML-embedded scripting language. • Only related to Java through syntax. • Dynamically typed and not object-oriented. • Provides a way to access elements of HTML documents and dynamically change them.

  28. Tools and Web Programming Languages Java • General purpose object-oriented programming language. • Based on C++, but simpler and safer. • Focus is on applets and servlets.

  29. Tools and Web Programming Languages Perl • Provides server-side computation for HTML documents, through CGI. • Perl is good for CGI programming because: • Direct access to operating systems functions • Powerful character string pattern-matching operations • Access to database systems

  30. Tools and Web Programming Languages • Perl is highly platform independent, and has been ported to all common platforms. • Perl is not just for CGI.

  31. Tools and Web Programming Languages PHP • A server-side scripting language. • An alternative to CGI. • Similar to JavaScript. • Great for form processing and database access through the Web.

  32. Tools and Web Programming Languages Tools for Creating Web Page • Adobe Dreamweaver (Latest version CS4) • Microsoft Front Page • Adobe PageMill

  33. Other info • Machines running specialized software called web sever store XHTML documents. • Netscape and Internet Explorer are the two most popular Web browsers. • ASP.NET is not an example of a platform-independent technology. • Authentication is commonly done through the use of logon password. • Authorization is the process of giving someone permission to do or have something • Logically, authorization is preceded (headed) by authentication.

  34. One of the most common security measures available to protect E-commerce sites is SSL • Lack of faith in E-Commerce site security is cited as the most common reason why people refuse to shop online. • FTP is the acronym for File Transfer Protocol. • HTTPS is the same way as HTTP but used securely. • WWW introduced in 1990 by Tim Berners-Lee. • An Internet Service Provider is a company that provides individuals and other companies access to the Internet and other related services. • A client is the requesting program in a client/server relationship.

  35. References • Programming the World Wide Web, Second Edition Author: Robert W. Sebesta Publisher: Addison-Wesley • NetStrider Tutorial: Uniform Resource Locators <http://www.netstrider.com/tutorials/URL/> Last accessed: 22nd June 2009

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