1 / 16

T171: You, Your Computer, and the Internet [Part B]

T171: You, Your Computer, and the Internet [Part B]. Bassam Bokhowa tobassam@hotmail.com. Section 6: Development of the Web. Visionaries & Developers.

seth-horne
Télécharger la présentation

T171: You, Your Computer, and the Internet [Part B]

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. T171: You, Your Computer, and the Internet[Part B] Bassam Bokhowa tobassam@hotmail.com

  2. Section 6: Development of the Web

  3. Visionaries & Developers Vannevar Bush: MIT scientist. In 1945, published an article titled “As we may think” describing an information storage and retrieval machine called Memex (memory extender). It was the most influential text in the creation of the World Wide Web. It inspired Douglas Engelbartand Ted Nelson. • Douglas Engelbart: A Navy radar technician who became a computer scientist inspired by Bush and Licklider. He realized that the development of the digital computer meant that the tools for ‘augmenting’ the human intellect were finally at hand and invented many of the fundamentals of the modern PC GUI, including the ‘mouse’,and video conferencing. He also invented a system to link documents similar to the Web called NLS.

  4. Visionaries & Developers Ted Nelson: created the hypertext concept; a document that has many links to jump to other documents. Nelson started Project Xanaduin 1960 (see: xanadu.com/nxu) to construct a global hypertext publishing system. It inspired similar projects, some of which were more successful. Bill Atkinson: Author of MacPaint, the graphics program for the Apple Macintosh. He invented HyperCard and its programming language:HyperTalk, whichissaid to be the first Hypermedia system for PCs, the core of which was an electronic card with user-installed ‘hot-spots’ which, when clicked on, would instantly cause a jump to another card. A group of linked cards was called a ‘stack’ and its key card was called … a ‘home’ card !

  5. Tim Berners-Lee The Web gave the Internet the same usability the GUI gave to PCs. It was key to the Internet’s explosive use and massive popularity. The Web was invented in 1989 by Tim Berners-Lee in the Physics laboratory center at CERN (the European Center for Nuclear Research) in Geneva. To help manage the complexity of retrieving CERN project information from different computers he needed a system that would: • Allow remote access to information across networks • Allow access of the same information from different types of computer systems • Be non-centralized • Be able to handle access to already existing data • Enable users to add their own private links • Enable ‘live’ links to be made between dynamically changing data

  6. Tim Berners-Lee To Implement such a system, Berners-Lee’s invention needed the following key elements: • Hypertext & Hypermedia system utilizing some form of a markup language for documents. • Browser: a client application which communicates with a server using a Universal Resource Locator (URL), and provides a window through which the user sees the Hypertext documents. • Server: which stores the files that are web resources and handles the requests for connection and transfer of these files to the ‘browser’ program. • Protocol: by which different machines can talk to one another and exchange information.

  7. Hypertext & Hypermedia • Hypertext - as an idea - is not exclusively confined to computer-based text. The footnotes in a conventional printed book are an example of hypertext in action. • There is a mark in the text (number or symbol) which diverts you from the main body of text to the footnote which is printed elsewhere, either at the foot of the page or at the end of the book. • The footnote itself may then lead you somewhere else, either within the book you are reading or to some other book or article. • The only difference is: computerized hypertext automatically takes you to the other text whereas with the conventional footnote you have to locate it yourself.

  8. Hypertext & Hypermedia • Hypertext itself is an old idea, the term being invented by Ted Nelson. • What is new in the Tim Berners-Lee implementation of Hypertext is: • Using the Internet as the network medium to link between Hypertext documents • The invention of the HyperText Markup Language (HTML) based on the SGML ISO standard • Hypermedia is a simple extension of Hypertext whereby image, sound, animation, and video are used alongside text.

  9. The Web Browser • The idea of a browser as a software tool for viewing and navigating through a web of hypertext documents was well established in the Hypertext community before Berners-Lee started designing the WWW. • For example, in the mid 1980s the Xerox NoteCards system enabled users to create a network of electronic ‘notecards’ connected by arbitrary (user-defined) links. The system had a browser tool which provided an editable graphical portrayal of some part of a notecard network. • Tim introduced a browser with the new concept of a Unified Resource Locator (URL) as a standard used to locate web documents, e.g. http://www.google.com

  10. The Web Browser • There are two main types of browsers, graphics-based and text-based. • The first version of the text-based (line-mode) browser was written by Nicola Pellow. • The most famous text-based browser is Lynx which is available for most operating systems including Microsoft Windows. • Text-based browsers have the following advantages over graphics-based browsers: • Smaller and require less RAM and system resources • Faster at retrieving information • Can run on hand-held computers (PDAs), mobile phones and the more elaborate pagers. • They can be used by a visually impaired person using a screen reader

  11. The Web Browser • Disadvantages of text-based browsers: • Cannot handle images (which the WWW relies on heavily) • Cannot deal with sites which are structured using frames • The first web browser (WorldWideWeb) was created by Tim Bernerds-Lee and was graphics-based. • Text based browsers have been overshadowed by graphics-based browsers (Opera, Internet Explorer, Netscape Navigator, Mosaic, etc.) since they can handle all types of information including images, sound, etc. • The World Wide Web Consortium (W3C.org) is the international body which oversees the Web and lays down its standards (e.g. HTML) to which - in theory - all browsers should adhere. • Browsers tend to have little quirks (changes) built into them by their designers To give their products a competitive edge.

  12. The Web Server • Web software (e.g. Apache or IIS) runs on a server to enable it to reply to the many requests it receives for the web (HTML) documents stored on the server. • The web browser requesting a document from the server (e.g. http://aou.org.bh/index.htm) is acting as a client to the server.

  13. The HTTP Protocol • In order for browsers and servers to communicate while residing on different machines using different operating systems, Berners-Lee had come up with a set of rules (a protocol) to allow different machines to talk to one another and exchange information. • The HyperText Transfer Protocol (HTTP) defines that a web transaction should be done in four stages: connection, request, reply and end. • This is also similar in the FTP protocol’s concept.

  14. Browser Wars • The first of the famous graphical browser programs was Mosaic by Marc Andreessen and Eric Bina of the National Center for Supercomputer Applications (NCSA) in spring 1993. • It was the Killer Application for the Web. It included a better way of handling images in web pages and changed the Web from hypertext to hypermedia. • Mosaic had many properties that contributed to the explosion of Internet usage by regular users • The first browser to run on regular PCs • A GUI application • Very easy to use • Designed to interpret the HTML <IMG> tag, thus introducing images into web pages • After leaving NCSA, Andreessen and his team wrote new code for a better browser: Netscape Navigator.

  15. Browser Wars • This enabled Andreessen to produce a cleaner, more secure and more sophisticated package which was distributed freely through the Internet to regular users and it quickly became the most used browser. • Throughout 1995 Netscape’s share price rocketed and their browser became the de facto standard and Mosaic was no longer desired. • Microsoft bought the Mosaic rights, renamed it Internet Explorer, and distributed it free with the Windows 95 operating system. • This created the browser war between the two companies (Microsoft and Netscape) and later resulted in the Justice Department filing a major anti-trust lawsuit against Microsoft. • Netscape lost market share and decided to release the source code under an Open Source license to let the power of the Internet continue the development of Navigator under the Mozilla project.

  16. Visit for T171 related videos: www.youtube.com/tobassam Thank You BassamBokhowa.com

More Related