计算机专业毕业论文翻译

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1、 1 The NetWorks Birth of the Net The 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

2、 nuclear 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

3、 of networks 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 backbo

4、ne service. 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 t

5、aken over the operation of the major Internet arteries, NSF has withdrawn from the backbone business.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 Solut

6、ions, Inc., in cooperation with NSF. How the Web Works The 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 co

7、mmunication 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 route

8、rs and 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: 2 Lets say you want to pay a visit to the the Louvre museum website. First you enter the a

9、ddress or 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 compu

10、ter screen. 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 file

11、s on the 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 Mi

12、crosoft 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 History The World Wide Web (WWW) was originally developed in 1990 at CERN, the European

13、Laboratory 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

14、to promote 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

15、National Center 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 soft

16、ware for scientific 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

17、 can think of the World Wide Web as a network of electronic files stored on computers all around the world. Hypertext links these resources together. Uniform Resource Locators or URLs are the addresses used to locate these files. The information contained in a URL gives you the ability to jump from

18、one web page to another with just a click of your mouse. When you type a URL into your 3 browser or click on a hypertext link, your browser is sending a request to a remote computer to download a file. What does a typical URL look like? Here are some examples: http:/ The home page for study english.

19、 ftp:/rtfm.mit.edu/pub/ A directory of files at MIT* available for downloading. news:rec.gardens.roses A newsgroup on rose gardening. The first part of a URL (before the two slashes* tells you the type of resource or method of access at that address. For example: http - a hypertext document or direc

20、tory gopher - a gopher document or menu ftp - a file available for downloading or a directory of such files news - a newsgroup telnet - a computer system that you can log into over the Internet WAIS* - a database or document in a Wide Area Information Search database file - a file located on a local

21、 drive (your hard drive) The second part is typically the address of the computer where the data or service is located. Additional parts may specify the names of files, the port to connect to, or the text to search for in a database. You can enter the URL of a site by typing it into the Location bar

22、 of your web browser, just under the toolbar. Most browsers record URLs that you want to use again, by adding them to a special menu. In Netscape Navigator, its called Bookmarks. In Microsoft Explorer, its called Favorites. Once you add a URL to your list, you can return to that web page simply by c

23、licking on the name in your list, instead of retyping the entire URL. Most of the URLs you will be using start with http which stands for Hypertext Transfer Protocol*. http is the method by which HTML files are transferred over the Web. Here are some other important things to know about URLs: A URL

24、usually has no spaces. A URL always uses forward slashes (/). If you enter a URL incorrectly, your browser will not be able to locate the site or resource you want. Should you get an error message or the wrong site, make sure you typed the address correctly. You can find the URL behind any link by passing your mouse cursor over the link. The pointer will turn into a hand and the URL will appear in the browsers status bar, usually located at the bottom of your screen.