Essay World Wide Web!
The Internet was a haven for academics and researchers till 1990. Unfortunately, these two groups were the only major users of the Internet till then.
In 1990, Tim Berners Lee, a physicist from CERN (the European nuclear research agency), invented and implemented on the Internet, an application called the World Wide Web. This application made it possible for a site on the Internet to have hundreds of pages, containing text, pictures, sound and video containing links to other pages.
These pages may be on any other server and these different servers may be physically located at distances that may be thousands of mile apart. By simply pointing his mouse pointer to the link and clicking the mouse, the reader can be immediately taken to the page pointed to by the link. For example, an organisation can have its home page that has links to other pages within the site or even to other sites.
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This has been made possible by the World Wide Web and the Mosaic viewer (developed by Marc Andreessen for the National Centre for Supercomputer Applications). When the viewer was first released, the number of servers on the net shot up from 100 to 7000. Mosaic is a browser that along with the World Wide Web skyrocketed the use of the Internet.
Incidentally, the fame that Marc Andreessen got from the wide use of his product, made him leave his job and form a company well known today as Netscape Communications. In 1994, the World Wide Web consortium was formed.
The functions of this consortium were to popularize the web and to standardize the necessary protocols. The latest information about the World Wide Web can be found at their website whose address is www(dot)w3(dot)org.
The World Wide Web is a client server system and from the user’s viewpoint, it consists of a vast collection of pages. Many pages are linked to each other by a method called hyperlinks and such pages (that point to other pages) are called hypertext. These links can be used very simply, by pointing the cursor at the link and clicking. The page to which the link is pointing will be promptly displayed.
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These pages are fetched and viewed using a program called a browser of which Mosaic was the first. There are many other browsers available such as Netscape navigator, Internet browser and Lynx. Of these, Lynx is a non-graphical browser and, therefore, not very popular.
However, when hypertext pages also contain other media such as audio and video clips, then they may not be viewable by all browsers. When such data is received by the user’s browser, it refers to a configuration file to find out how to view such data. This file tells the browser the name of the external viewer program, which it then uses.
Most browsers use the user’s disk to cache pages that have been fetched. Before getting a page, the disk cache is first checked to see whether the page already exists on the disk and whether it is updated. If it does exist then it is not fetched. When using the “Back” button on the screen, this may be observed, since the response is very fast because the page is fetched directly from the cache.
To host a Web browser, the machine must be either directly connected to the Internet or connected through a router to the Internet.
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The browser first establishes a TCP connection to the location where the desired page exists and then sends the message asking for the page. This makes it essential for the browser to be connected either directly, or via router, to the Internet. From the server’s point of view, it has a TCP port (port 80) which listens for any incoming browser request from a user.
When such a request comes from a user comes to establish a TCP connection, it is established and then the request is complied with and the page requested is sent. The connection is then broken. The protocol that defines these requests and responses is known as the Hypertext Transfer Protocol, generally referred to by the abbreviation HTTP. Next, we shall look at what is known by the abbreviation URL.