計(jì)算機(jī)專(zhuān)業(yè)畢業(yè)論文翻譯

1、<p>　　The NetWorks</p><p>　　Birth of the Net</p><p>　　The Internet has had a relatively brief, but explosive history so far. It grew out of an experiment begun in the 1960's by the U.S.

2、 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 nuclear war. If part of the network were damaged or destroyed, the rest of the sys

3、tem still had to work. That network was ARPANET, which linked U.S. scientific and academic researchers. It was the forerunner of today's Internet. </p><p>　　In 1985, the National Science Foundation (NSF)

4、 created NSFNET, a series 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.

5、At the same time, regional networks were created to link individual institutions with the national backbone service. </p><p>　　NSFNET grew rapidly as people discovered its potential, and as new software appl

6、ications 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 over th

7、e operation of the major Internet arteries, NSF has withdrawn from the backbone business. </p><p>　　NSF also coordinated a service called InterNIC, which registered all addresses on the Internet so that data

8、 could be routed to the right system. This service has now been taken over by Network Solutions, Inc., in cooperation with NSF. </p><p>　　How the Web Works</p><p>　　The World Wide Web, the graph

9、ical 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 commun

10、ication by displaying text, graphics, animation, photos, sound and video. </p><p>　　So just what is this miraculous creation? The Web physically consists of your personal computer, web browser software, a co

11、nnection to an Internet service provider, computers called servers that host digital data and routers and switches to direct the flow of information. </p><p>　　The Web is known as a client-server system. You

12、r computer is the client; the remote computers that store electronic files are the servers. Here's how it works: </p><p>　　Let's say you want to pay a visit to the the Louvre museum website. First yo

13、u enter the address 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 Louvre's site. The Louvre's server sends the dat

14、a over the Internet to your computer. Your web browser interprets the data, displaying it on your computer screen. </p><p>　　The Louvre's website also has links to the sites of other museums, such as the

15、 Vatican Museum. When you click your mouse on a link, you access the web server for the Vatican Museum. </p><p>　　The "glue" that holds the Web together is called hypertext and hyperlinks. This fea

16、ture allow electronic files 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 brow

17、sing or surfing the Net. </p><p>　　To access the Web you need web browser software, such as Netscape Navigator or Microsoft Internet Explorer. How does your web browser distinguish between web pages and othe

18、r files on the Internet? Web pages are written in a computer language called Hypertext Markup Language or HTML.</p><p>　　Some Web History</p><p>　　The World Wide Web (WWW) was originally develop

19、ed in 1990 at CERN, the European Laboratory for Particle Physics. It is now managed by The World Wide Web Consortium, also known as the World Wide Web Initiative. </p><p>　　The WWW Consortium is funded by a

20、large number of corporate members, including AT&T, Adobe Systems, Inc., Microsoft Corporation and Sun Microsystems, Inc. Its purpose is to promote the growth of the Web by developing technical specifications and refe

21、rence 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. <

22、/p><p>　　The 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 We

23、b features created by CERN. NCSA focuses on improving the productivity of researchers by providing software for scientific modeling, analysis, and visualization. The World Wide Web was an obvious way to fulfill that miss

24、ion. NCSA Mosaic, one of the earliest web browsers, was distributed free to the</p><p>　　Understanding Web Addresses </p><p>　　You can think of the World Wide Web as a network of electronic file

25、s 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 abili

26、ty to jump from one web page to another with just a click of your mouse. When you type a URL into your browser or click on a hypertext link, your browser is sending a request to a remote computer to download a fil</p&

27、gt;<p>　　What does a typical URL look like? Here are some examples:　　http://english.chinaschool.net/ 　　The home page for study english. </p><p>　　ftp://rtfm.mit.edu/pub/ </p><p>　　A di

28、rectory of files at MIT* available for downloading. </p><p>　　news:rec.gardens.roses </p><p>　　A newsgroup on rose gardening. </p><p>　　The first part of a URL (before the two slash

29、es* tells you the type of resource or method of access at that address. For example: </p><p>　　http - a hypertext document or directory </p><p>　　gopher - a gopher document or menu </p>&

30、lt;p>　　ftp - a file available for downloading or a directory of such files </p><p>　　news - a newsgroup </p><p>　　telnet - a computer system that you can log into over the Internet </p>

31、<p>　　WAIS* - a database or document in a Wide Area Information Search database </p><p>　　file - a file located on a local drive (your hard drive) </p><p>　　The second part is typically t

32、he 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. </p><p>　　You can enter the

33、URL of a site by typing it into the Location bar of your web browser, just under the toolbar. </p><p>　　Most browsers record URLs that you want to use again, by adding them to a special menu. In Netscape Nav

34、igator, it's called Bookmarks. In Microsoft Explorer, it's called Favorites. Once you add a URL to your list, you can return to that web page simply by clicking on the name in your list, instead of retyping the e

35、ntire URL. </p><p>　　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

36、 important things to know about URLs:</p><p>　　A URL usually has no spaces. </p><p>　　A URL always uses forward slashes (//). </p><p>　　If you enter a URL incorrectly, your browser

37、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. </p><p>　　You can find the URL behind any link by passi

38、ng your mouse cursor over the link. The pointer will turn into a hand and the URL will appear in the browser's status bar, usually located at the bottom of your screen.</p><p>　　Domain Names</p>&

39、lt;p>　　When you think of the Internet, you probably think of ".com." Just what do those three letters at the end of a World Wide Web address mean? </p><p>　　Every computer that hosts data on the

40、 Internet has a unique numerical address. For example, the numerical address for the White House is 198.137.240.100. But since few people want to remember long strings of numbers, the Domain Name System (DNS)* was develo

41、ped. DNS, a critical part of the Internet's technical infrastructure*, correlates* a numerical address to a word. To access the White House website, you could type its number into the address box of your web browser.

42、 But most people prefer to </p><p>　　In general, the three-letter domain name suffix* is known as a generic top-level domain and describes the type of organization. In the last few years, the lines have some

43、what blurred* between these categories. .com - business (commercial) .edu - educational .org - non-profit .mil - military .net - network provider .gov - government </p><p>　　A domain name always has tw

44、o or more parts separated by dots and typically consists of some form of an organization's name and the three-letter suffix. For example, the domain name for IBM is "ibm.com"; the United Nations is "un

45、.org." </p><p>　　If a domain name is available, and provided it does not infringe* on an existing trademark, anyone can register the name for $35 a year through Network Solutions, Inc., which is authori

46、zed to register .com, .net and .org domains. You can use the box below to see if a name is a available. Don't be surprised if the .com name you want is already taken, however. Of the over 8 million domain names, 85%

47、are .com domains. </p><p>　　ICANN, the Internet Corporation for Assigned Names and Numbers, manages the Domain Name System. As of this writing, there are plans to add additional top-level domains, such as .w

48、eb and .store. When that will actually happen is anybody's guess. </p><p>　　To check for, or register a domain name, type it into the search box.It should take this form: myname.com </p><p>

49、;　　In addition to the generic top-level domains, 244 national top-level domains were established for countries and territories*, for example: </p><p>　　.au - Australia .ca - Canada .fr - France .de - Germ

50、any .uk - United Kingdom </p><p>　　For US $275 per name, you can also register an international domain name with Net Names. Be aware that some countries have restrictions for registering names. </p>

51、<p>　　If you plan to register your own domain name, whether it's a .com or not, keep these tips in mind: </p><p>　　The shorter the name, the better. (But it should reflect your family name, interest

52、 or business.) The name should be easy to remember. It should be easy to type without making mistakes. Remember, the Internet is global. Ideally, a domain name will "read" in a language other than English. &

53、lt;/p><p>　　About Modem</p><p>　　Telephone lines were designed to carry the human voice, not electronic data from a computer. Modems were invented to convert digital computer signals into a form th

54、at allows them to travel over the phone lines. Those are the scratchy sounds you hear from a modem's speaker. A modem on the other end of the line can understand it and convert the sounds back into digital informatio

55、n that the computer can understand. By the way, the word modem stands for MOdulator/DEModulator. </p><p>　　Buying and using a modem used to be relatively easy. Not too long ago, almost all modems transferred

56、 data at a rate of 2400 Bps (bits per second). Today, modems not only run faster, they are also loaded with features like error control and data compression. So, in addition to converting and interpreting signals, modems

57、 also act like traffic cops, monitoring and regulating the flow of information. That way, one computer doesn't send information until the receiving computer is ready for it. Each o</p><p>　　If your compu

58、ter didn't come with an internal modem, consider buying an external one, because it is much easier to install and operate. For example, when your modem gets stuck (not an unusual occurrence), you need to turn it off

59、and on to get it working properly. With an internal modem, that means restarting your computer--a waste of time. With an external modem it's as easy as flipping a switch. </p><p>　　Here's a tip for y

60、ou: in most areas, if you have Call Waiting, you can disable it by inserting *70 in front of the number you dial to connect to the Internet (or any online service). This will prevent an incoming call from accidentally ki

61、cking you off the line. </p><p>　　This table illustrates the relative difference in data transmission speeds for different types of files. A modem's speed is measured in bits per second (bps). A 14.4 mod

62、em sends data at 14,400 bits per second. A 28.8 modem is twice as fast, sending and receiving data at a rate of 28,800 bits per second. </p><p>　　Until nearly the end of 1995, the conventional wisdom was tha

63、t 28.8 Kbps was about the fastest speed you could squeeze out of a regular copper telephone line. Today, you can buy 33.6 Kbps modems, and modems that are capable of 56 Kbps. The key question for you, is knowing what spe

64、ed modems your Internet service provider (ISP) has. If your ISP has only 28.8 Kbps modems on its end of the line, you could have the fastest modem in the world, and only be able to connect at 28.8 Kbps. Before you inves&

65、lt;/p><p>　　Speed It Up</p><p>　　There are faster ways to transmit data by using an ISDN or leased line. In many parts of the U.S., phone companies are offering home ISDN at less than $30 a month.

66、ISDN requires a so-called ISDN adapter instead of a modem, and a phone line with a special connection that allows it to send and receive digital signals. You have to arrange with your phone company to have this equipment

67、 installed. For more about ISDN, visit Dan Kegel's ISDN Page. </p><p>　　An ISDN line has a data transfer rate of between 57,600 bits per second and 128,000 bits per second, which is at least double the r

68、ate of a 28.8 Kbps modem. Leased lines come in two configurations: T1 and T3. A T1 line offers a data transfer rate of 1.54 million bits per second. Unlike ISDN, a T-1 line is a dedicated connection, meaning that it is p

69、ermanently connected to the Internet. This is useful for web servers or other computers that need to be connected to the Internet all the time. It is</p><p>　　Leased lines are very expensive and are generall

70、y only used by companies whose business is built around the Internet or need to transfer massive amounts of data. ISDN, on the other hand, is available in some cities for a very reasonable price. Not all phone companies

71、offer residential ISDN service. Check with your local phone company for availability in your area. </p><p>　　Cable Modems </p><p>　　A relatively new development is a device that provides high-

72、speed Internet access via a cable TV network. With speeds of up to 36 Mbps, cable modems can download data in seconds that might take fifty times longer with a dial-up connection. Because it works with your TV cable, it

73、doesn't tie up a telephone line. Best of all, it's always on, so there is no need to connect--no more busy signals! This service is now available in some cities in the United States and Europe. </p><p&

74、gt;　　The download times in the table above are relative and are meant to give you a general idea of how long it would take to download different sized files at different connection speeds, under the best of circumstances

75、. Many things can interfere with the speed of your file transfer. These can range from excessive line noise on your telephone line and the speed of the web server from which you are downloading files, to the number of ot

76、her people who are simultaneously trying to access the same file </p><p><b>　　DSL</b></p><p>　　DSL (Digital Subscriber Line) is another high-speed technology that is becoming increas

77、ingly popular. DSL lines are always connected to the Internet, so you don't need to dial-up. Typically, data can be transferred at rates up to 1.544 Mbps downstream and about 128 Kbps upstream over ordinary telephone

78、 lines. Since a DSL line carries both voice and data, you don't have to install another phone line. You can use your existing line to establish DSL service, provided service is available in your ar</p><p&g

79、t;　　DSL service requires a special modem. Prices for equipment, DSL installation and monthly service can vary considerably, so check with your local phone company and Internet service provider. The good news is that pric

80、es are coming down as competition heats up.</p><p><b>　　Websites</b></p><p>　　Anatomy of a Web Page</p><p>　　A web page is an electronic document written in a computer l

81、anguage called HTML, short for Hypertext Markup Language. Each web page has a unique address, called a URL* or Uniform Resource Locator, which identifies its location on the network. </p><p>　　A website has

82、one or more related web pages, depending on how it's designed. Web pages on a site are linked together through a system of hyperlinks* , enabling you to jump between them by clicking on a link. On the Web, you naviga

83、te through pages of information according to your interests. Home Sweet Home Page</p><p>　　When you browse the World Wide Web you'll see the term home page often. Think of a home page as the starting p

84、oint of a website. Like the table of contents of a book or magazine, the home page usually provides an overview of what you'll find at the website. A site can have one page, many pages or a few long ones, depending o

85、n how it's designed. If there isn't a lot of information, the home page may be the only page. But usually you will find at least a few other pages. </p><p>　　Web pages vary wildly in design and conte

86、nt, but most use a traditional magazine format. At the top of the page is a masthead* or banner graphic*, then a list of items, such as articles, often with a brief description. The items in the list usually link to othe

87、r pages on the website, or to other sites. Sometimes these links are highlighted* words in the body of the text, or are arranged in a list, like an index. They can also be a combination* of both. A web page can also have

88、 images that link t</p><p>　　How can you tell which text are links? Text links appear in a different color from the rest of the text--typically in blue and underlined. When you move your cursor over a text l

89、ink or over a graphic link, it will change from an arrow to a hand. The hypertext words often hint* at what you will link to. </p><p>　　When you return to a page with a link you've already visited, the h

90、ypertext words will often be in a different color, so you know you've already been there. But you can certainly go there again. Don't be surprised though, if the next time you visit a site, the page looks differe

91、nt and the information has changed. The Web is a dynamic* medium. To encourage visitors to return to a site, some web publishers change pages often. That's what makes browsing the Web so exciting</p><p>

92、　　A Home (Page) of Your Own</p><p>　　In the 60s, people asked about your astrological* sign. In the 90s, they want to know your URL. These days, having a web address is almost as important as a street addres

93、s. Your website is an electronic meeting place for your family, friends and potentially*, millions of people around the world. Building your digital domain can be easier than you may think. Best of all, you may not have

94、to spend a cent. The Web brims with all kinds of free services, from tools to help you build your site, to fre</p><p>　　Think of your home page as the starting point of your website. Like the table of conten

95、ts of a book or magazine, the home page is the front door. Your site can have one or more pages, depending on how you design it. If there isn't a lot of information just yet, your site will most likely have only a ho

96、me page. But the site is sure to grow over time. </p><p>　　While web pages vary dramatically* in their design and content, most use a traditional magazine layout. At the top of the page is a banner graphic.

97、Next comes a greeting and a short description of the site. Pictures, text, and links to other websites follow. </p><p>　　If the site has more than one page, there's typically a list of items--similar to

98、an index--often with a brief description. The items in the list link to other pages on the website. Sometimes these links are highlighted words in the body of the text. It can also be a combination of both. Additionally,

99、 a web page may have images that link to other content.  </p><p>　　Before you start building your site, do some planning. Think about whom the site is for and what you want to say. Next, gather up the m