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1、The NetWorksBirth of the NetThe Internet has had a relatively brief, but explosive history so far. It grew out of an experiment begun in the 1960s by the U.S. Department of Defense. The DoD wanted to create a computer network that would continue to function in the event of a disaster, such as a nucl
2、ear war. If part of the network were damaged or destroyed, the rest of the system still had to work. That network was ARPANET, which linked U.S. scientific and academic researchers. It was the forerunner of todays Internet. In 1985, the National Science Foundation (NSF) created NSFNET, a series of n
3、etworks for research and education communication. Based on ARPANET protocols, the NSFNET created a national backbone service, provided free to any U.S. research and educational institution. At the same time, regional networks were created to link individual institutions with the national backbone se
4、rvice. NSFNET grew rapidly as people discovered its potential, and as new software applications were created to make access easier. Corporations such as Sprint and MCI began to build their own networks, which they linked to NSFNET. As commercial firms and other regional network providers have taken
5、over the operation of the major Internet arteries, NSF has withdrawn from the backbone business. NSF also coordinated a service called InterNIC, which registered all addresses on the Internet so that data could be routed to the right system. This service has now been taken over by Network Solutions,
6、 Inc., in cooperation with NSF. How the Web WorksThe World Wide Web, the graphical portion of the Internet, is the most popular part of the Internet by far. Once you spend time on the Web,you will begin to feel like there is no limit to what you can discover. The Web allows rich and diverse communic
7、ation by displaying text, graphics, animation, photos, sound and video. So just what is this miraculous creation? The Web physically consists of your personal computer, web browser software, a connection to an Internet service provider, computers called servers that host digital data and routers and
8、 switches to direct the flow of information. The Web is known as a client-server system. Your computer is the client; the remote computers that store electronic files are the servers. Heres how it works: Lets say you want to pay a visit to the the Louvre museum website. First you enter the address o
9、r URL of the website in your web browser (more about this shortly). Then your browser requests the web page from the web server that hosts the Louvres site. The Louvres server sends the data over the Internet to your computer. Your web browser interprets the data, displaying it on your computer scre
10、en. The Louvres website also has links to the sites of other museums, such as the Vatican Museum. When you click your mouse on a link, you access the web server for the Vatican Museum. The glue that holds the Web together is called hypertext and hyperlinks. This feature allow electronic files on the
11、 Web to be linked so you can easily jump between them. On the Web, you navigate through pages of information based on what interests you at that particular moment, commonly known as browsing or surfing the Net. To access the Web you need web browser software, such as Netscape Navigator or Microsoft
12、Internet Explorer. How does your web browser distinguish between web pages and other files on the Internet? Web pages are written in a computer language called Hypertext Markup Language or HTML.Some Web HistoryThe World Wide Web (WWW) was originally developed in 1990 at CERN, the European Laboratory
13、 for Particle Physics. It is now managed by The World Wide Web Consortium, also known as the World Wide Web Initiative. The WWW Consortium is funded by a large number of corporate members, including AT&T, Adobe Systems, Inc., Microsoft Corporation and Sun Microsystems, Inc. Its purpose is to promote
14、 the growth of the Web by developing technical specifications and reference software that will be freely available to everyone. The Consortium is run by MIT with INRIA (The French National Institute for Research in Computer Science) acting as European host, in collaboration with CERN. The National C
15、enter for Supercomputing Applications (NCSA) at the University of Illinois at Urbana-Champaign, was instrumental in the development of early graphical software utilizing the World Wide Web features created by CERN. NCSA focuses on improving the productivity of researchers by providing software for s
16、cientific modeling, analysis, and visualization. The World Wide Web was an obvious way to fulfill that mission. NCSA Mosaic, one of the earliest web browsers, was distributed free to the public. It led directly to the phenomenal growth of the World Wide Web.Understanding Web Addresses You can think of the World Wide Web as a network of electronic files stored on computers all around the world. Hypertext
