计算机专业毕业设计外文翻译
计算机毕业设计外文翻译
Hibernate. 其中，服务器端表示层由 Struts 框架来描
述 MVC 框架，业务逻辑层由 Spring 框架的 IoC 容器
来协助完成，持久层由 Hibernate 框架的对象关系映
射 (O/R Mapping) 来完成与数据库的交互，服务器端
表示层和业务逻辑层通过域模型层的 VO (Value
在多层结构设计中，提倡的是对接口进行编程的设计方式，在编程中只引用接口而不用具体的实现类，
在装载时才配置具体的实现类实例. 如接口类 TestDao(TestBean 是我们要处理的持久化类)定义如下:
public interface TestDao// 接口类 void createBean( TestBean Testbean) throws DataAccessException// 持久化 void updateBean(TestBean Testbean) throws DataAccessExcept void deleteBean(int Te stldω) throws DataAccessException; 臼 矿扩删 除垛 Bean l
采用新的高效的开发模式，并且随着 ]ava 组件的迅速开发，许多技术包括 AOP 和 IoC 为 JavaBeans 提供了
很多像 E]B 才拥有的强大功能，为 ]avaBeans 提供了类似 E]B 的声明式编程模型，但并没有带来任何像 E]B
那样的复杂问题 [I J • ]2EE 复杂的多层结构、庞大的体系决定了 ]2EE 项目需要运用框架和设计模式来控制
以定义所要配置的属性以及要注入的值.可以注入任何东西，从基本类型到集合类，甚至是应用系统中的其 他 Bean ，也可以通过 <ref> 标签注入.
软件工程毕业论文文献翻译中英文对照
软件工程毕业论文文献翻译中英文对照学生毕业设计(论文)外文译文学生姓名: 学号专业名称:软件工程译文标题(中英文):Qt Creator白皮书(Qt Creator Whitepaper)译文出处:Qt network 指导教师审阅签名: 外文译文正文:Qt Creator白皮书Qt Creator是一个完整的集成开发环境(IDE)，用于创建Qt应用程序框架的应用。
Qt是专为应用程序和用户界面，一次开发和部署跨多个桌面和移动操作系统。
本文提供了一个推出的Qt Creator和提供Qt开发人员在应用开发生命周期的特点。
Qt Creator的简介Qt Creator的主要优点之一是它允许一个开发团队共享一个项目不同的开发平台(微软Windows?的Mac OS X?和Linux?)共同为开发和调试工具。
Qt Creator的主要目标是满足Qt开发人员正在寻找简单，易用性，生产力，可扩展性和开放的发展需要，而旨在降低进入新来乍到Qt的屏障。
Qt Creator 的主要功能，让开发商完成以下任务: , 快速，轻松地开始使用Qt应用开发项目向导，快速访问最近的项目和会议。
, 设计Qt物件为基础的应用与集成的编辑器的用户界面，Qt Designer中。
, 开发与应用的先进的C + +代码编辑器，提供新的强大的功能完成的代码片段，重构代码，查看文件的轮廓(即，象征着一个文件层次)。
, 建立，运行和部署Qt项目，目标多个桌面和移动平台，如微软Windows，Mac OS X中，Linux的，诺基亚的MeeGo，和Maemo。
, GNU和CDB使用Qt类结构的认识，增加了图形用户界面的调试器的调试。
, 使用代码分析工具，以检查你的应用程序中的内存管理问题。
, 应用程序部署到移动设备的MeeGo，为Symbian和Maemo设备创建应用程序安装包，可以在Ovi商店和其他渠道发布的。
, 轻松地访问信息集成的上下文敏感的Qt帮助系统。
计算机专业毕业设计外文翻译
外文翻译Birth of the NetThe 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. 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 system still had to work. That network was ARPANET, which linked U.S. scientific and academic researchers. It was the forerunner of today's Internet.In 1985, the National Science Foundation (NSF) 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. At the same time, regional networks were created to link individual institutions with the national backbone 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 taken 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, 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 communication 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 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. Here's how it works:Let's say you want to pay a visit to the the Louvre museum website. First you 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 data over the Internet to your computer. Your web browser interprets the data, displaying it on your computer screen.The Louvre's 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 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 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 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 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 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 software 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 AddressesYou 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 thesefiles. The information contained in a URL gives you the ability 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 file.What does a typical URL look like? Here are some examples:/The home page for study english.ftp:///pub/A directory of files at MIT* available for downloading.news:rec.gardens.rosesA 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 directory•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 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 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, 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 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 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 browser's status ba r, usually located at the bottom of your screen.Domain NamesWhen 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?Every computer that hosts data on the Internet has a unique numerical address. For example, the numerical address for the White House is198.137.240.100. But since few people want to remember long strings of numbers, the Domain Name System (DNS)* was developed. 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. But most people prefer to use "." In this case, the domain name is . In general, the three-letter domain name suffix* is known as a generictop-level domai n and describes the type of organization. In the last few years, the lines have somewhat blurred* between these categories..com - business (commercial).edu - educational.org - non-profit.mil - military.net - network provider.gov - governmentA domain name always has two 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 ""; the United Nations is "."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 authorized 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 ifthe .com name you want is already taken, however. Of the over 8 million domain names, 85% are .com domains.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 .web and .store. When that will actually happen is anybody's guess.To check for, or register a domain name, type it into the search box.It should take this form: In addition to the generic top-level domains, 244 national top-level domains were established for countries and territories*, for example:.au - Australia.ca - Canada.fr - France.de - Germany.uk - United KingdomFor 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.If you plan to register your own domain name, whether it's a .com or not, keep these tips in mind:The shorter the name, the better. (But it should reflect your family name, interest 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.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 that allows them to travel over the phone lines. Those are the scratchy sounds you hear from a modem's speaker. A modem on theother end of the line can understand it and convert the sounds back into digital information that the computer can understand. By the way, the word modem stands for MOdulator/DEModulator.Buying and using a modem used to be relatively easy. Not too long ago, almost all modems transferred 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 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 of these features, modulation, error control, and data compression, requires a separate kind of protocol and that's what some of those terms you see like V.32, V.32bis, V.42bis and MNP5 refer to.If your computer 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 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.Here's a tip for you: 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 kicking you off the line.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 modem 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.Until nearly the end of 1995, the conventional wisdom was that 28.8 Kbps was about the fastest speed you could squeeze out of a regular copper telephoneline. Today, you can buy 33.6 Kbps modems, and modems that are capable of 56 Kbps. The key question for you, is knowing what speed 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 invest in a 33.6 Kbps or a 56 Kbps modem, make sure your ISP supports them.Speed It UpThere 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. 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 installed. For more about ISDN, visit Dan Kegel's ISDN Page.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 rate 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 permanently 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 possible to lease only a portion of a T-1 line using one of two systems: fractional T-1 or Frame Relay. You can lease them in blocks ranging from 128 Kbps to 1.5 Mbps. The differences are not worth going into in detail, but fractional T-1 will be more expensive at the slower available speeds and Frame Relay will be slightly more expensive as you approach the full T-1 speed of 1.5 Mbps. A T-3 line is significantly faster, at 45 million bits per second. The backbone of the Internet consists of T-3 lines. Leased lines are very expensive and are generally only used by companies whose business is built around the Internet or need to transfer massiveamounts of data. ISDN, on the other hand, is available in some cities for a very reasonable price. Not all phone companies offer residential ISDN service. Check with your local phone company for availability in your area.Cable ModemsA relatively new development is a device that provides high-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 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.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. 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 other people who are simultaneously trying to access the same file or other files in the same directory.DSLDSL (Digital Subscriber Line) is another high-speed technology that is becoming increasingly 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 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 DSLservice, provided service is available in your area and you are within the specified distance from the telephone company's central switching office.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 prices are coming down as competition heats up.Anatomy of a Web PageA web page is an electronic document written in a computer language 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.A website has 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 navigate through pages of information according to your interests.Home Sweet Home PageWhen you browse the World Wide Web you'll see the term home page often. Think of a home page as the starting point 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 on 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.Web pages vary wildly in design and content, 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 other 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 images that link to other content.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 yourcursor over a text link 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.When you return to a page with a link you've already visited, the hypertext 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 different 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 excitingA Home (Page) of Your OwnIn 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 address. 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 to spend a cent. The Web brims with all kinds of free services, from tools to help you build your site, to free graphics, animation and site hosting. All it takes is some time and creativity.Think of your home page as the starting point of your website. Like the table of contents 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 home page. But the site is sure to grow over time.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. Next comes a greeting and a short description of the site. Pictures, text, and links to other websites follow.If the site has more than one page, there's typically a list of items--similar to 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, a web page may have images that link to other content.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 material that you wantto put on the site: write the copy, scan the photos, design or find the graphics. Draw a rough layout on a sheet of paper.While there are no rules you have to follow, there are a few things to keep in mind:•Start simply. If you are too ambitious at the beginning, you may never get the site off the ground. You can always add to your site.•Less is better. Most people don't like to read a lot of text online. Break it into small chunks.•Use restraint. Although you can use wild colors and images for the background of your pages, make sure your visitors will be able to readthe text easily.•Smaller is better. Most people connect to the Internet with a modem.Since it can take a long time to download large image files, keep the file sizes small.•Have the rights. Don't put any material on your site unless you are sure you can do it legally. Read Learn the Net's copyright article for moreabout this.Stake Your ClaimNow it's time to roll up your sleeves and start building. Learn the Net Communities provides tools to help you build your site, free web hosting, and a community of other homesteaders.Your Internet service provider may include free web hosting services with an account, one alternative to consider.Decoding Error MessagesAs you surf the Net, you will undoubtedly find that at times you can't access certain websites. Why, you make wonder? Error messages attempt to explain the reason. Unfortunately, these cryptic* messages baffle* most people.We've deciphered* the most common ones you may encounter.400 - Bad RequestProblem: There's something wrong with the address you entered. You may not be authorized* to access the web page, or maybe it no longer exists.Solution: Check the address carefully, especially if the address is long. Make sure that the slashes are correct (they should be forward slashes) and that all the names are properly spelled. Web addresses are case sensitive, socheck that the names are capitalized in your entry as they are in the original reference to the website.401 - UnauthorizedProblem: You can't access a website, because you're not on the guest list, your password is invalid or you have entered your password incorrectly.Solution: If you think you have authorization, try typing your password again. Remember that passwords are case sensitive.403 - ForbiddenProblem: Essentially the same as a 401.Solution: Try entering your password again or move on to another site.404 - Not FoundProblem: Either the web page no longer exists on the server or it is nowhere to be found.Solution: Check the address carefully and try entering it again. You might also see if the site has a search engine and if so, use it to hunt for the document. (It's not uncommon for pages to change their addresses when a website is redesigned.) To get to the home page of the site, delete everything after the domain name and hit the Enter or Return key.503 - Service unavailableProblem: Your Internet service provider (ISP) or your company's Internet connection may be down.Solution: Take a stretch, wait a few minutes and try again. If you still have no luck, phone your ISP or system administrator.Bad file requestProblem: Your web browser may not be able to decipher the online form you want to access. There may also be a technical error in the form.Solution: Consider sending a message to the site's webmaster, providing any technical information you can, such as the browser and version you use.Connection refused by hostProblem: You don't have permission to access the page or your password is incorrect.Solution: Try typing your password again if you think you should have access.Failed DNS lookupProblem: DNS stands for the Domain Name System, which is the system that looks up the name of a website, finds a corresponding number (similar to a phone number), then directs your request to the appropriate web server on theInternet. When the lookup fails, the host server can't be located.Solution: Try clicking on the Reload or Refresh button on your browser toolbar. If this doesn't work, check the address and enter it again. If all else fails, try again later.File contains no dataProblem: The site has no web pages on it.Solution: Check the address and enter it again. If you get the same error message, try again later.Host unavailableProblem: The web server is down.Solution: Try clicking on the Reload or Refresh button. If this doesn't work, try again later.Host unknownProblem: The web server is down, the site may have moved, or you've been disconnected from the Net.Solution: Try clicking on the Reload or Refresh button and check to see that you are still online. If this fails, try using a search engine to find the site. It may have a new address.Network connection refused by the serverProblem: The web server is busy.Solution: Try again in a while.Unable to locate hostProblem: The web server is down or you've been disconnected from the Net.Solution: Try clicking on the Reload or Refresh button and check to see that you are still online.Unable to locate serverProblem: The web server is out-of-business or you may have entered the address incorrectly.Solution: Check the address and try typing it again.Web BrowsersA web browser is the software program you use to access the World Wide Web, the graphical portion of the Internet. The first browser, called NCSA Mosaic, was developed at the National Center for Supercomputing Applications in the early '90s. The easy-to-use point-and-click interface*helped popularize the Web, although few then could imagine the explosive growth that would soon occur.Although many different browsers are available, Microsoft Internet Explorer* and Netscape Navigator* are the two most popular ones. Netscape and Microsoft have put so much money into their browsers that the competition can't keep up. The pitched battle* between the two companies to dominate* the market has lead to continual improvements to the software. Version 4.0 and later releases of either browser are excellent choices. (By the way, both are based on NCSA Mosaic.) You can download Explorer and Navigator for free from each company's website. If you have one browser already, you can test out the other. Also note that there are slight differences between the Windows and MacIntosh* versions.You can surf to your heart's content, but it's easy to get lost in this electronic web. That's where your browser can really help. Browsers come loaded with all sorts of handy features. Fortunately, you can learn the basics in just a few minutes, then take the time to explore the advanced functions.Both Explorer and Navigator have more similarities than differences, so we'll primarily cover those. For the most up-to-date information about the browsers, and a complete tutorial, check the online handbook under the Help menu or go to the websites of the respective* software companies.Browser AnatomyWhen you first launch your web browser, usually by double-clicking on the icon on your desktop, a predefined web page, your home page, will appear. With Netscape Navigator for instance, you will be taken to Netscape's NetCenter.•The Toolbar （工具栏）The row of buttons at the top of your web browser, known as the toolbar, helps you travel through the web of possibilities, even keeping track ofwhere you've been. Since the toolbars for Navigator and Explorer differ slightly, we'll first describe what the buttons in common do:o The Back button returns you the previous page you've visited.o Use the Forward button to return to the page you just came from.o Home takes you to whichever home page you've chosen. (If you haven't selected one, it will return you to the default home page,usually the Microsoft or Netscape website.)。
计算机专业毕业设计外文翻译--JSP内置对象
附录1 外文参考文献（译文）JSP内置对象有些对象不用声明就可以在JSP页面的Java程序片和表达式部分使用，这就是JSP 的内置对象。
JSP的内置对象有：request、response、session、application、out.response和request对象是JSP内置对象中较重要的两个，这两个对象提供了对服务器和浏览器通信方法的控制。
直接讨论这两个对象前，要先对HTTP协议—Word Wide Wed底层协议做简单介绍。
Word Wide Wed是怎样运行的呢？在浏览器上键入一个正确的网址后，若一切顺利，网页就出现了。
使用浏览器从网站获取HTML页面时，实际在使用超文本传输协议。
HTTP规定了信息在Internet上的传输方法，特别是规定吧浏览器与服务器的交互方法。
从网站获取页面时，浏览器在网站上打开了一个对网络服务器的连接，并发出请求。
服务器收到请求后回应，所以HTTP协议的核心就是“请求和响应”。
一个典型的请求通常包含许多头，称作请求的HTTP头。
头提供了关于信息体的附加信息及请求的来源。
其中有些头是标准的，有些和特定的浏览器有关。
一个请求还可能包含信息体，例如，信息体可包含HTML表单的内容。
在HTML表单上单击Submit 键时，该表单使用ACTION=”POST”或ACTION=”GET”方法，输入表单的内容都被发送到服务器上。
该表单内容就由POST方法或GET方法在请求的信息体中发送。
服务器发送请求时，返回HTTP响应。
响应也有某种结构，每个响应都由状态行开始，可以包含几个头及可能的信息体，称为响应的HTTP头和响应信息体，这些头和信息体由服务器发送给客户的浏览器，信息体就是客户请求的网页的运行结果，对于JSP 页面，就是网页的静态信息。
用户可能已经熟悉状态行，状态行说明了正在使用的协议、状态代码及文本信息。
例如，若服务器请求出错，则状态行返回错误及对错误描述，比如HTTP/1.1 404 Object Not Found。
毕业设计(论文)外文资料翻译(学生用)
毕业设计外文资料翻译学院：信息科学与工程学院专业：软件工程姓名： XXXXX学号： XXXXXXXXX外文出处： Think In Java (用外文写)附件： 1.外文资料翻译译文；2.外文原文。
附件1：外文资料翻译译文网络编程历史上的网络编程都倾向于困难、复杂，而且极易出错。
程序员必须掌握与网络有关的大量细节，有时甚至要对硬件有深刻的认识。
一般地，我们需要理解连网协议中不同的“层”（Layer）。
而且对于每个连网库，一般都包含了数量众多的函数，分别涉及信息块的连接、打包和拆包；这些块的来回运输；以及握手等等。
这是一项令人痛苦的工作。
但是，连网本身的概念并不是很难。
我们想获得位于其他地方某台机器上的信息，并把它们移到这儿；或者相反。
这与读写文件非常相似，只是文件存在于远程机器上，而且远程机器有权决定如何处理我们请求或者发送的数据。
Java最出色的一个地方就是它的“无痛苦连网”概念。
有关连网的基层细节已被尽可能地提取出去，并隐藏在JVM以及Java的本机安装系统里进行控制。
我们使用的编程模型是一个文件的模型；事实上，网络连接（一个“套接字”）已被封装到系统对象里，所以可象对其他数据流那样采用同样的方法调用。
除此以外，在我们处理另一个连网问题——同时控制多个网络连接——的时候，Java内建的多线程机制也是十分方便的。
本章将用一系列易懂的例子解释Java的连网支持。
15.1 机器的标识当然，为了分辨来自别处的一台机器，以及为了保证自己连接的是希望的那台机器，必须有一种机制能独一无二地标识出网络内的每台机器。
早期网络只解决了如何在本地网络环境中为机器提供唯一的名字。
但Java面向的是整个因特网，这要求用一种机制对来自世界各地的机器进行标识。
为达到这个目的，我们采用了IP（互联网地址）的概念。
IP以两种形式存在着：(1) 大家最熟悉的DNS（域名服务）形式。
我自己的域名是。
所以假定我在自己的域内有一台名为Opus的计算机，它的域名就可以是。
毕业设计 计算机专业外文翻译--基于Socket的网络编程
题目Programming Overlay Networkswith Overlay SocketsProgramming Overlay Networks with Overlay Sockets The emergence of application-layer overlay networks has inspired the development of new network services and applications. Research on overlay net-workshas focused on the design of protocols to maintain and forward data in an overlay network, however, less attention has been given to the software development process of building application programs in such an environment. Clearly,the complexity of overlay network protocols calls for suitable application programming interfaces (APIs) and abstractions that do not require detailed knowledge of the overlay protocol, and, thereby, simplify the task of the application programmer. In this paper, we present the concept of an overlay socket as a new programming abstraction that serves as the end point of communication in an overlay network. The overlay socket provides a socket-based API that is independent of the chosen overlay topology, and can be configured to work for different overlay topologies. The overlay socket can support application data transfer over TCP, UDP, or other transport protocols. This paper describes the design of the overlay socket and discusses API and configuration options.1 IntroductionApplication-layer overlay networks [5, 9, 13, 17] provide flexible platforms for develop-ing new network services [1, 10, 11, 14, 18–20] without requiring changes to the network-layer infrastructure. Members of an overlay network, which can be hosts, routers, servers, or applications, organize themselves to form a logical network topology, and commu-nicate only with their respective neighbors in the overlay topology. A member of an overlay network sends and receives application data, and also forwards data intended for other members. This paper addresses application development in overlay networks. We use the term overlay network programming to refer to the software development process of building application programs that communicate with one another in anapplication-layer overlay_This work is supported in part by the National Science Foundation through grant work. The diversity and complexity of building and maintaining overlay networks make it impractical to assume that application developers can be concerned with the complexity of managing the participation of an application in a specific overlay networktopology.We present a software module, called overlay socket, that intends to simplify the task of overlay network programming. The design of the overlay socket pursues the following set of objectives: First, the application programming interface (API) of the overlay socket does not require that an application programmer has knowledge of the overlay network topology. Second, the overlay socket is designed to accommodate dif-ferent overlay network topologies. Switching to different overlay network topologies is done by modifying parameters in a configuration file. Third, the overlay socket, which operates at the applicationlayer,can accommodate different types of transport layer protocols. This is accomplished by using network adapters that interface to the un-derlying transport layer network and perform encapsulation and de-encapsulation of messages exchanged by the overlay socket. Currently available network adapters are TCP, UDP, and UDP multicast. Fourth, the overlay socket provides mechanisms for bootstrapping new overlay networks. In this paper, we provide an overview of the overlay socket design and discuss over-lay network programming with the overlay socket. The overlay socket has been imple-mented in Java as part of the HyperCast 2.0 software distribution [12]. The software has been used for various overlay applications, and has been tested in both local-area as well as wide-area settings. The HyperCast 2.0 software implements the overlay topolo-gies described in [15] and [16]. This paper highlights important issues of the overlay socket, additional information can be found in the design documentation available from[12]. Several studies before us have addressed overlay network programming issues. Even early overlay network proposals, such as Yoid [9], Scribe [4], and Scattercast [6], have presented APIs that aspire to achieve independence of the API from the overlay network topology used. Particularly, Yoid and Scattercast use a socket-like API, how-ever, these APIs do not address issues that arise when the same API is used by different overlaynetwork topologies. Several works on application-layer multicast overlays inte-grate the application program with the software responsible for maintaining the overlay network, without explicitly providing general-purpose APIs.These include Narada [5], Overcast [13], ALMI [17], and NICE [2]. A recent study [8] has proposed a common API for the class of so-called structured overlays, which includes Chord [19], CAN [18], and Bayeux [20], and other overlays that were originally motivated by distributed hash tables. Our work has a different emphasis than [8], since we assume a scenario where an application programmer must work with several, possibly fundamentally dif-ferent, overlay network topologies and different transmission modes (UDP, TCP), and, therefore, needs mechanisms that make it easy to change the configuration of the un-derlying overlay network..Internet Overlay socket Application Overlay socket Application Application Overlay socket Application Application Overlay socket Application Overlay Network.Fig. 1. The overlay network is a collection of overlay sockets. Root (sender) Root (receiver) (a) Multicast (b) Unicast.Fig. 2. Data forwarding in overlay networks.The rest of the paper is organized as following. In Section 2 we introduce con-cepts, abstractions, and terminology needed for the discussion of the overlay socket. In Section 3 we present the design of the overlay socket, and discuss its components. In Section 4 we show how to write programs using the overlay socket. We present brief conclusions in Section 5.2 Basic ConceptsAn overlay socket is an endpoint for communication in an overlay network, and an overlay network is seen as a collection of overlay sockets that self-organize using an overlay protocol (see Figure 1). An overlay socket offers to an application programmer a Berkeley socket-style API [3] for sending and receiving data over an overlay network. Each overlay socket executes an overlay protocol that is responsible for maintaining the membership of the socket in the overlay network topology. Each overlay socket has a logical address and a physical address in the overlay network. The logical address is dependent on the type of overlay protocol used. In the overlay protocols currentlyimplemented in HyperCast 2.0, the logical addresses are 32- bit integers or _x_y_coordinates, where x and y are positive 32-bit positive integers. The physical address is a transport layer address where overlay sockets receive messages from the overlay network. On the Internet, the physical address is an IP address and a TCP or UDP port number. Application programs that use overlay sockets only work with logical addresses, and do not see physical addresses of overlay nodes. When an overlay socket is created, the socket is configured with a set of configu-ration parameters, called attributes. The application program can obtain the attributes from a configuration file or it downloads the attributes from a server. The configuration file specifies the type of overlay protocol and the type of transport protocol to be used,.but also more detailed information such as the size of internal buffers, and the value of protocol-specific timers. The most important attribute is the overlay identifier (overlay ID) which is used as a global identifier for an overlay network and which can be used as a key to access the other attributes of the overlay network. Each new overlay ID corresponds to the creation of a new overlay network. Overlay sockets exchange two types of messages, protocol messages and application messages. Protocol messages are the messages of the overlay protocol that main-tain the overlay topology. Application messages contain applicationdata that is encap-sulatedn an overlay message header. An application message uses logical addresses in the header to identify source and, for unicast, the destination of the message. If an overlay socket receives an application message from one of its neighbors in the over-lay network, it determines if the message must be forwarded to other overlay sockets, and if the message needs to be passed to the local application. The transmission modes currently supported by the overlay sockets are unicast, and multicast. In multicast, all members in the overlay network are receivers.In both unicast and multicast,the com-mon abstractionfor data forwarding is that of passing data in spanning trees that are embedded in the overlay topology. For example, a multicast message is transmitted downstream a spanning tree that has the sender of the multicast message as the root (see Figure 2(a)). When an overlay socket receives a multicast message, it forwards the message to all of its downstream neighbors (children) in the tree, and passes the mes-sage to the local application program. A unicast message is transmitted upstream a tree with the receiver of the message as the root (see Figure 2(b)). An overlay socket that receives a unicast message forwards the message to the upstream neighbor (parent) in the tree that has the destination as the root. An overlay socket makes forwarding decisions locally using only the logical ad-dresses of its neighbors and the logical address of the root of the tree. Hence, there is a requirement that each overlay socket can locally compute its parent and its children in a tree with respect to a root node. This requirement is satisfied by many overlay network topologies, including [15, 16, 18–20].3 The Components of an Overlay SocketAn overlay socket consists of a collection of components that are configured when the overlay socketis created, using the supplied set of attributes. These components include the overlay protocol, which helps to build and maintain the overlay network topology, a component that processes application data, and interfaces to a transport-layer network. The main components of an overlay socket, as illustrated in Figure 3, are as follows:The overlay node implements an overlay protocol that establishes and maintains the overlay network topology. The overlay node sends and receives overlay protocol messages, and maintains a set of timers. The overlay node is the only component of an overlay socket that is aware of the overlay topology. In the HyperCast 2.0. Overlay socket Forwarding EngineApplication Programming InterfaceStatistics InterfaceProtocol MessagesApplicationReceiveBufferApplicationTransmitBuffer Overlay NodeO verlay NodeInterfac eNode AdapterAdapter InterfaceSocket AdapterA dapter InterfaceApplication MessagesApplication ProgramTransport-layer NetworkApplication MessagesFig. 3. Components of an overlay socket.software, there are overlay nodes that build a logical hypercube [15] and a logical Delaunay triangu-lartion [16].The forwarding engine performs the functions of an application-layer router, that sends, receives, and forwards formatted application-layer messages in the overlay network. The forwarding engine communicates with the overlay node to query next hop routing information for application messages. The forwarding decision is made using logical addresses of the overlay nodes. Each overlay socket has two network adapters that each provides an interface to transport-layer protocols, such as TCP or UDP. The node adapter serves as the in-terface for sending and receiving overlay protocol messages, and the socket adapter serves as the interface for application messages. Each adapter has a transport level address, which, in the case of the Internet, consists of an IP address and a UDP or TCP port number. Currently, there are three different types of adapters, for TCP,UDP, and UDP multicast. Using two adapters completely separates the handling of messages for maintaining the overlay protocol and the messages that transport application data.The application receive buffer and application transmit buffer can temporarily store messages that, respectively, have been received by the socket but not been deliv-ered to theapplication, or that have been released by the application program, but not been transmitted by the socket. The application transmit buffer can play a role when messages cannot be transmitted due to rate control or congestion control con-straints. The application transmit buffer is not implemented in the HyperCast 2.0 software.Each overlay socket has two external interfaces. The application programming in-terface (API) of the socket offers application programs the ability to join and leave existing overlays, to send data to other members of the overlay network, and receive data from the overlay network. The statistics interface of the overlay socket provides access to status information of components of the overlay socket, and is used for monitoring and management of an overlay socket. Note in Figure 3 that some components of the overlay socket also have interfaces, which are accessed by other components of the overlay socket. The overlay manager is a component external to the overlay socket (and not shown in Figure 3). It is responsible for configuring an overlay socket when the socket is created. The overlay manager reads a configuration file that stores the attributes of an overlay socket, and, if it is specified in the configuration file, may access attributes from a server, and then initiates the instantiation of a new overlay socket.4 Overlay Network ProgrammingAn application developer does not need to be familiar with the details of the components of an overlay socket as described in the previous section. The developer is exposed only to the API of the overlay socket and to a file with configuration parameters. The configuration file is a text file which stores all attributes needed to configure an overlay socket. The configuration file is modified whenever a change is needed to the transport protocol, the overlay protocol, or some other parameters of the overlay socket. In the following, we summarize only the main features of the API, and we refer to [12] fordetailed information on the overlay socket API.4.1 Overlay Socket APISince the overlay topology and the forwarding of application-layer data is transparent to the application program, the API for overlay network programming can be made simple. Applications need to be able to create a new overlay network, join and leave an existing overlay network, send data to and receive data from other members in the overlay.The API of the overlay socket is message-based, and intentionally stays close to the familiar Berkeley socket API [3]. Since space considerations do not permit a description of the full API, we sketch the API with the help of a simplified example. Figure 4 shows the fragment of a Java program that uses an overlay socket. An application program configures and creates an overlay socket with the help of an overlay manager (o m). The overlay manager reads configuration parameters for the overlay socket from a configu-ration file (hypercast.pro p), which can look similarly as shown in Figure 5. The applica-tion program reads the overlay ID with command om.getDefaultProperty(“OverlayID”) from the file, and creates an configuration object (confi g) for an overlay socket with the.// Generate the configuration objectOverlayManager om = newOverlayManager("hypercast.prop");String MyOverlay = om.getDefaultProperty("OverlayID");OverlaySocketConfig config = new om.getOverlaySocketConfig(MyOverlay);// create an overlay socketOL Socket socket = config.createOverlaySocket(callback);// Join an overlaysocket.joinGroup();// Create a messageOL Message msg = socket.createMessage(byte[] data, int length);// Send the message to all members in overlay networksocket.sendToAll(msg);// Receive a message from the socketOL Message msg = socket.receive();Fig. 4. Program with overlay sockets.# OVERLAY Server:OverlayServer =# OVERLAY ID:OverlayID = 1234KeyAttributes= Socket,Node,SocketAdapter# SOCKET:Socket = HCast2-0HCAST2-0.TTL = 255HCAST2-0.ReceiveBufferSize = 200# SOCKET ADAPTER:SocketAdapter = TCPSocketAdapter.TCP.MaximumPacketLength = 16384# NODE:Node = DT2-0DT2-0.SleepTime = 400# NODE ADAPTER:NodeAdapter = NodeAdptUDPServerNodeAdapter.UDP.MaximumPacketLength = 8192NodeAdapter.UDPServer.UdpServer0 =128.143.71.50:8081Fig. 5. Configuration file (simplified) given overlay ID. The configuration object also loads all configuration information from the configuration file, and then creates the overlay socket(config.createOverlaySocke t).Once the overlay socket is created, the socket joins the overlay network(socket.join-Grou p). When a socket wants to multicast a message, it instantiates a new message (socket.createMessage) and trans-mits the message using the sendToAll method. Other transmission options are send-To-Parent, send-To-Children, sendToNeighbors, and sendToNode, which, respectively, send a message to the upstream neighbor with respect to a given root (see Figure 2), to the downstream neighbors, to all neighbors, or to a particular node with a given logical address.4.2 Overlay Network Properties ManagementAs seen, the properties of an overlay socket are configured by setting attributes in a configuration file. The overlay manager in an application process uses the attributes to create a new overlay socket. By modifying the attributes in the configuration file, an application programmer can configure the overlay protocol or transport protocol that is used by the overlay socket. Changes to the file must be done before the socket is created. Figure 5 shows a (simplified) example of a configuration file. Each line of the configuration file assigns a value to an attribute. The complete list of attributes and the range of values is documented in [12]. Without explaining all entries in Figure 5, the file sets, among others, the overlay ID to …1234 ‟, selects version 2.0 of the DT protocol as overlay protocol (…Node=DT2-0 ‟), and it sets the transport protocol of the socket adaptor to TCP(…SocketAdapter=TCP ‟).Each overlay network is associated with a set of attributes that characterize the properties of the over-lay sockets that participate in the overlay network. As mentioned earlier, the most important attribute is the overlay ID, which is used to identify an y network, and which can be used as a key toaccess all other attributes of an overlay network. The overlay ID should be a globally unique identifier.A new overlay network is created by generating a new overlay ID and associating aset of attributes that specify the properties of the overlay sockets in the overlay network. To join an overlay network, an overlay socket must know the overlay ID and the set of attributes for this overlay ID. This information can be obtained from a configuration file, as shown in Figure 5.All attributes have a name and a value, both of which are strings. For example, the overlay protocol of an overlay socket can be determined by an attribute with name NODE. If the attribute is set to NOD-E=DT2- 0, then the overlay node in the overlay socket runs the DT (version 2) overlay protocol. The overlay socket distinguishes between two types of attributes: key attributes and configurable attributes. Key attributes are specific to an overlay network with a given overlay ID. Key attributes are selectedwhen the overlay ID is created for an overlay network, and cannot be modified after-wards.Overlay sockets that participate in an overlay network must have identical key attributes, but can have different configurable attributes. The attributes OverlayID and KeyAttributes are key attributes by default in all overlay networks. Configurable at-tributes specify parameters of an overlay socket, which are not considered essential for establishing communication between overlay sockets in the same overlay network, and which are considered …tunable‟.5 ConclusionsWe discussed the design of an overlay socket which attempts to simplify the task of overlay network programming. The overlay socket serves as an end point of commu-nication in the overlay network. The overlay socket can be used for various overlay topologies and support different transport protoc-ols. The overlay socket supports a simple API for joining and leaving an overlay network, and for sending and receiving data to and from other sockets in the overlay network. The main advantage of the overlay socket is that it is relatively easy to change the configuration of the overlay network. An implementation of the overlay socket is distributed with the HyperCast2.0 soft-ware. The software has been extensively tested. Avariety of different applications, such as distributed whiteboard and a video streaming application, have been developed with the overlay sockets.Acknowledgement. In addition to the authors of this article the contributors include Bhupinder Sethi, Tyler Beam, Burton Filstrup, Mike Nahas, Dongwen Wang, Konrad Lorincz, Jean Ablutz, Haiyong Wang, Weisheng Si, Huafeng Lu, and Guangyu Dong.基于Socket的网络编程应用层覆盖网络的出现促进了新网络服务和应用的发展。
计算机专业毕业设计论文外文文献中英文翻译——java对象
1 . Introduction To Objects1.1The progress of abstractionAll programming languages provide abstractions. It can be argued that the complexity of the problems you’re able to solve is directly related to the kind and quality of abstraction。
By “kind” I mean，“What is it that you are abstracting?” Assembly language is a small abstraction of the underlying machine. Many so—called “imperative” languages that followed （such as FORTRAN，BASIC, and C) were abstractions of assembly language。
These languages are big improvements over assembly language，but their primary abstraction still requires you to think in terms of the structure of the computer rather than the structure of the problem you are trying to solve。
The programmer must establish the association between the machine model (in the “solution space，” which is the place where you’re modeling that problem, such as a computer) and the model of the problem that is actually being solved (in the “problem space,” which is the place where the problem exists). The effort required to perform this mapping, and the fact that it is extrinsic to the programming language，produces programs that are difficult to write and expensive to maintain，and as a side effect created the entire “programming methods” industry.The alter native to modeling the machine is to model the problem you’re trying to solve。
计算机科学与技术外文翻译
Working with Strings
Strings are characters or words. String values must always be enclosed in either single quotesor double quotes. Here are a few examples of strings:
In ActionScript, you’ll work with many different datatypes. However, for the sake of understandinghow these datatypes work, you can consider them in two basic categories: primitivetypes and reference types. The primitive types are called primitive because they are the basicfoundational datatypes, not because they lack importance. The reference datatypes are calledreference types because they reference the primitive types.
计算机外文翻译（完整）
计算机外⽂翻译（完整）毕业设计(论⽂)外⽂资料翻译专业：计算机科学与技术姓名：王成明学号：06120186外⽂出处：The History of the Internet附件： 1.外⽂原⽂ 2.外⽂资料翻译译⽂；附件1：外⽂原⽂The History of the InternetThe Beginning - ARPAnetThe Internet started as a project by the US government. The object of the project was to create a means of communications between long distance points, in the event of a nation wide emergency or, more specifically, nuclear war. The project was called ARPAnet, and it is what the Internet started as. Funded specifically for military communication, the engineers responsible for ARPANet had no idea of the possibilities of an "Internet."By definition, an 'Internet' is four or more computers connected by a network.ARPAnet achieved its network by using a protocol called TCP/IP. The basics around this protocol was that if information sent over a network failed to get through on one route, it would find another route to work with, as well as establishing a means for one computer to "talk" to another computer, regardless of whether it was a PC or a Macintosh.By the 80's ARPAnet, just years away from becoming the more well known Internet, had 200 computers. The Defense Department, satisfied with ARPAnets results, decided to fully adopt it into service, and connected many military computers and resources into the network. ARPAnet then had 562 computers on its network. By the year 1984, it had over 1000 computers on its network.In 1986 ARPAnet (supposedly) shut down, but only the organization shut down, and the existing networks still existed between the more than 1000 computers. It shut down due to a failied link up with NSF, who wanted to connect its 5 countywide super computers into ARPAnet.With the funding of NSF, new high speed lines were successfully installed at line speeds of 56k (a normal modem nowadays) through telephone lines in 1988. By that time, there were 28,174 computers on the (by then decided) Internet. In 1989 there were 80,000 computers on it. By 1989, there were290,000.Another network was built to support the incredible number of people joining. It was constructed in 1992.Today - The InternetToday, the Internet has become one of the most important technological advancements in the history of humanity. Everyone wants to get 'on line' to experience the wealth of information of the Internet. Millions of people now use the Internet, and it's predicted that by the year 2003 every single person on the planet will have Internet access. The Internet has truly become a way of life in our time and era, and is evolving so quickly its hard to determine where it will go next, as computer and network technology improve every day.HOW IT WORKS:It's a standard thing. People using the Internet. Shopping, playing games,conversing in virtual Internet environments.The Internet is not a 'thing' itself. The Internet cannot just "crash." It functions the same way as the telephone system, only there is no Internet company that runs the Internet.The Internet is a collection of millioins of computers that are all connected to each other, or have the means to connect to each other. The Internet is just like an office network, only it has millions of computers connected to it.The main thing about how the Internet works is communication. How does a computer in Houston know how to access data on a computer in Tokyo to view a webpage?Internet communication, communication among computers connected to the Internet, is based on a language. This language is called TCP/IP. TCP/IP establishes a language for a computer to access and transmit data over the Internet system.But TCP/IP assumes that there is a physical connecetion between onecomputer and another. This is not usually the case. There would have to be a network wire that went to every computer connected to the Internet, but that would make the Internet impossible to access.The physical connection that is requireed is established by way of modems,phonelines, and other modem cable connections (like cable modems or DSL). Modems on computers read and transmit data over established lines,which could be phonelines or data lines. The actual hard core connections are established among computers called routers.A router is a computer that serves as a traffic controller for information.To explain this better, let's look at how a standard computer might viewa webpage.1. The user's computer dials into an Internet Service Provider (ISP). The ISP might in turn be connected to another ISP, or a straight connection into the Internet backbone.2. The user launches a web browser like Netscape or Internet Explorer and types in an internet location to go to.3. Here's where the tricky part comes in. First, the computer sends data about it's data request to a router. A router is a very high speed powerful computer running special software. The collection of routers in the world make what is called a "backbone," on which all the data on the Internet is transferred. The backbone presently operates at a speed of several gigabytes per-second. Such a speed compared to a normal modem is like comparing the heat of the sun to the heat of an ice-cube.Routers handle data that is going back and forth. A router puts small chunks of data into packages called packets, which function similarly to envelopes. So, when the request for the webpage goes through, it uses TCP/IP protocols to tell the router what to do with the data, where it's going, and overall where the user wants to go.4. The router sends these packets to other routers, eventually leadingto the target computer. It's like whisper down the lane (only the information remains intact).5. When the information reaches the target web server, the webserver then begins to send the web page back. A webserver is the computer where the webpage is stored that is running a program that handles requests for the webpage and sends the webpage to whoever wants to see it.6. The webpage is put in packets, sent through routers, and arrive at the users computer where the user can view the webpage once it is assembled.The packets which contain the data also contain special information that lets routers and other computers know how to reassemble the data in the right order.With millions of web pages, and millions of users, using the Internet is not always easy for a beginning user, especially for someone who is not entirely comfortale with using computers. Below you can find tips tricks and help on how to use main services of the Internet.Before you access webpages, you must have a web browser to actually be able to view the webpages. Most Internet Access Providers provide you with a web browser in the software they usually give to customers; you. The fact that you are viewing this page means that you have a web browser. The top two use browsers are Netscape Communicator and Microsoft Internet Explorer. Netscape can be found at /doc/bedc387343323968011c9268.html and MSIE can be found at /doc/bedc387343323968011c9268.html /ie.The fact that you're reading this right now means that you have a web browser.Next you must be familiar with actually using webpages. A webpage is a collection of hyperlinks, images, text, forms, menus, and multimedia. To "navigate" a webpage, simply click the links it provides or follow it's own instructions (like if it has a form you need to use, it will probably instruct you how to use it). Basically, everything about a webpage is made to be self-explanetory. That is the nature of a webpage, to be easily navigatable."Oh no! a 404 error! 'Cannot find web page?'" is a common remark made by new web-users.Sometimes websites have errors. But an error on a website is not the user's fault, of course.A 404 error means that the page you tried to go to does not exist. This could be because the site is still being constructed and the page hasn't been created yet, or because the site author made a typo in the page. There's nothing much to do about a 404 error except for e-mailing the site administrator (of the page you wanted to go to) an telling him/her about the error.A Javascript error is the result of a programming error in the Javascript code of a website. Not all websites utilize Javascript, but many do. Javascript is different from Java, and most browsers now support Javascript. If you are using an old version of a web browser (Netscape 3.0 for example), you might get Javascript errors because sites utilize Javascript versions that your browser does not support. So, you can try getting a newer version of your web browser.E-mail stands for Electronic Mail, and that's what it is. E-mail enables people to send letters, and even files and pictures to each other.To use e-mail, you must have an e-mail client, which is just like a personal post office, since it retrieves and stores e-mail. Secondly, you must have an e-mail account. Most Internet Service Providers provide free e-mail account(s) for free. Some services offer free e-mail, like Hotmail, and Geocities.After configuring your e-mail client with your POP3 and SMTP server address (your e-mail provider will give you that information), you are ready to receive mail.An attachment is a file sent in a letter. If someone sends you an attachment and you don't know who it is, don't run the file, ever. It could be a virus or some other kind of nasty programs. You can't get a virus justby reading e-mail, you'll have to physically execute some form of program for a virus to strike.A signature is a feature of many e-mail programs. A signature is added to the end of every e-mail you send out. You can put a text graphic, your business information, anything you want.Imagine that a computer on the Internet is an island in the sea. The sea is filled with millions of islands. This is the Internet. Imagine an island communicates with other island by sending ships to other islands and receiving ships. The island has ports to accept and send out ships.A computer on the Internet has access nodes called ports. A port is just a symbolic object that allows the computer to operate on a network (or the Internet). This method is similar to the island/ocean symbolism above.Telnet refers to accessing ports on a server directly with a text connection. Almost every kind of Internet function, like accessing web pages,"chatting," and e-mailing is done over a Telnet connection.Telnetting requires a Telnet client. A telnet program comes with the Windows system, so Windows users can access telnet by typing in "telnet" (without the "'s) in the run dialog. Linux has it built into the command line; telnet. A popular telnet program for Macintosh is NCSA telnet.Any server software (web page daemon, chat daemon) can be accessed via telnet, although they are not usually meant to be accessed in such a manner. For instance, it is possible to connect directly to a mail server and check your mail by interfacing with the e-mail server software, but it's easier to use an e-mail client (of course).There are millions of WebPages that come from all over the world, yet how will you know what the address of a page you want is?Search engines save the day. A search engine is a very large website that allows you to search it's own database of websites. For instance, if you wanted to find a website on dogs, you'd search for "dog" or "dogs" or "dog information." Here are a few search-engines.1. Altavista (/doc/bedc387343323968011c9268.html ) - Web spider & Indexed2. Yahoo (/doc/bedc387343323968011c9268.html ) - Web spider & Indexed Collection3. Excite (/doc/bedc387343323968011c9268.html ) - Web spider & Indexed4. Lycos (/doc/bedc387343323968011c9268.html ) - Web spider & Indexed5. Metasearch (/doc/bedc387343323968011c9268.html ) - Multiple searchA web spider is a program used by search engines that goes from page to page, following any link it can possibly find. This means that a search engine can literally map out as much of the Internet as it's own time and speed allows for.An indexed collection uses hand-added links. For instance, on Yahoo's site. You can click on Computers & the Internet. Then you can click on Hardware. Then you can click on Modems, etc., and along the way through sections, there are sites available which relate to what section you're in.Metasearch searches many search engines at the same time, finding the top choices from about 10 search engines, making searching a lot more effective.Once you are able to use search engines, you can effectively find the pages you want.With the arrival of networking and multi user systems, security has always been on the mind of system developers and system operators. Since the dawn of AT&T and its phone network, hackers have been known by many, hackers who find ways all the time of breaking into systems. It used to not be that big of a problem, since networking was limited to big corporate companies or government computers who could afford the necessary computer security.The biggest problem now-a-days is personal information. Why should you be careful while making purchases via a website? Let's look at how the internet works, quickly.The user is transferring credit card information to a webpage. Looks safe, right? Not necessarily. As the user submits the information, it is being streamed through a series of computers that make up the Internet backbone.The information is in little chunks, in packages called packets. Here's the problem: While the information is being transferred through this big backbone, what is preventing a "hacker" from intercepting this data stream at one of the backbone points?Big-brother is not watching you if you access a web site, but users should be aware of potential threats while transmitting private information. There are methods of enforcing security, like password protection, an most importantly, encryption.Encryption means scrambling data into a code that can only be unscrambled on the "other end." Browser's like Netscape Communicator and Internet Explorer feature encryption support for making on-line transfers. Some encryptions work better than others. The most advanced encryption system is called DES (Data Encryption Standard), and it was adopted by the US Defense Department because it was deemed so difficult to 'crack' that they considered it a security risk if it would fall into another countries hands.A DES uses a single key of information to unlock an entire document. The problem is, there are 75 trillion possible keys to use, so it is a highly difficult system to break. One document was cracked and decoded, but it was a combined effort of14,000 computers networked over the Internet that took a while to do it, so most hackers don't have that many resources available.附件2：外⽂资料翻译译⽂Internet的历史起源——ARPAnetInternet是被美国政府作为⼀项⼯程进⾏开发的。
【计算机专业文献翻译】信息系统的管理
传播媒体必须经过仔细选择，平衡每个媒体的优点和缺点，这个选择决定网络的速度。改变一个已经安装好的网络媒体通常非常昂贵。最实用的传播媒体是电缆，光纤，广播，光，红外线。
本科生毕业设计（论文）外文资料译文
（2009届）
论文题目
基于Javamail的邮件收发系统
学生姓名
学号
专业
计算机科学与技术
班级
指导教师
职称
讲师、副教授
填表日期
2008年 12月 10 日
信息科学与工程学院教务科制
外文资料翻译（译文不少于2000汉字）
1．所译外文资料：信息系统的管理Managing Information Systems
数据共享是网络的重要应用之一。网络可以共享交易数据，搜索和查询数据，信息，公告板，日历，团队和个人信息数据，备份等。在交易的时候，连接一个公司的电脑的中央数据库包括现有库存信息和出售的数据信息。如果数据被储存在一个中央数据库中，搜查结果便可从中获取。电子邮件的发送已经成为同事之间最常用的信息共享的方式之一。
自从信号在空中传输后，广播，光以及红外线作为传播媒体已经不需要电缆。
传输能力，即一个传播媒体一次性传输的数据量，在不同的媒体中，材料不同，安装时付出的劳动不同，传输的能力有很大的区别。传播媒体有时候被合并，代替远地域之间的高速传播媒体，速度虽慢，但是成本低，在一幢大楼中进行信息传播。
连接设备包括网络连接卡NICS，或者在计算机和网络间进行传输和信号传递的局域网LAN卡。其他常用的设备连接不同的网络，特别是当一个网络使用不用的传输媒体的时候。使用一个对很多用户都开放的系统很重要，比如windows/NT,Office2000，Novell，UNIX.
计算机类毕业外文翻译---系统开发阶段
计算机类毕业外文翻译The Phase to Develop the systemWith the society's development, the personal relationship is day by day intense. How enhances the personal relationship, reduces the management cost, the enhancement service level and pensonal competitive ability, is every one superintendent most matter of concern. More and more superintendents thought the implementation computer scientific style management solves this question.Management information systems (MIS), are information systems, typically computer based, that are used within an organization. World net described an information system as‖ a system consisting of the network of all communication channels used with an organization‖.Generally speaking, MIS involved the following parts:1 Conduct a Preliminary Investigation（1）What is the objective of the first phase of the SDLC?Attention: SDLC means Systems Development Life Cycle.The objectives of phase 1, preliminary investigation, are to conduct a preliminary analysis, propose alternative solutions, describe the costs and benefits of each solution, and submit a preliminary plan with recommendations. The problems are briefly identified and a few solutions are suggested. This phase is often called a feasibility study.（2）Conduct the preliminary analysisIn this step, you need to find out what the organization’s objectives are and to explore the nature and scope of the problems under study.Determine the organization’s objectives: Even if a problem pertains to only a small segment of the organization, you cannot study it in isolation. You need to find out what the overall objectives of the organization are and how groups and departments with in the organization interact. Then you need to examine the problem in that context.Determine the nature and scope of the problems: you may already have a sense of the nature and scope of a problem. However, with a fuller understanding of the goals of the organization, you can now take a closer look at the specifics. Is too much time being wasted on paperwork? On waiting for materials? On nonessential tasks? How pervasive is the problem within the organization? Outside of it? What people are most affected? And so on. Your reading and your interviews should give you a sense of the character of the problem.（3）Propose alternative solutionsIn delving into the organization’s objectives and the specific problems, you may have already discovered some solutions. Other possible solutions may be generated by interviewing people inside the organization, clients or customers, suppliers, and consultants and by studying what competitors are doing. With this data, you then have three choices. You can leave the system as is, improve it, or develop a new system.Leave the system as is: often, especially with paper-based or no technological systems, the problem really isn’t bad enough to justify the measures and expenditures required to get rid of it.Improve the system: sometimes changing a few key elements in the system upgrading to a new computer or new software, or doing a bit of employee retraining, for example will do the trick. Modifications might be introduced over several months, if the problem is no serious.Develop a new system: if the existing system is truly harmful to the organization, radical changes may be warranted. A new system would not mean just tinkering around the edges or introducing some new piece of hardware or software. It could mean changes in every part and at every level.（4）Describe costs and benefitsWhichever of the three alternatives is chose, it will have costs and benefits. In this step, you need to indicate what these are.The changes or absence of changes will have a price tag, of course, and you need to indicate what it is. Greater costs may result in greater benefits, which, in turn, may offer savings. The benefits may be both tangible—such as costly savings –and intangible—such as worker satisfaction. A process may be speeded up, streamlined through the elimination of unnecessary steps, or combined with other processes. Input errors or redundant output may be reduced. Systems and subsystems may be better integrated. Users may be happier with the system. Customers or suppliers may interact more efficiently with the system. Security may be improved. Costs may be cut.（5）Submit a preliminary planNow you need to wrap up all your findings in a written report, submitted to the executives(probably top managers) who are in a position to decide in which direction to proceed—make no changes, change a little, or change a lot—and how much money to allow the project. You should describe the potential solutions, costs, and benefits and indicate your recommendations. If management approves the feasibility study, then the systems analysis phase can begin.2 Do a Detailed Analysis of the System（1）What tools are used in the second phase of the SDLC to analyze data?The objectives of phase 2, systems analysis, are to gather data, analyze the data, and write a report. The present system is studied in depth, and new requirements are specified. Systems analysis describes what a system is already doing and what it should do to meet the needs of users. Systems design—the next phase—specifies how the system will accommodate the objective.In this second phase of the SDLC, you will follow the course prescribed by management on the basis of your phase/feasibility report. We are assuming what you have been directed to perform phase 2—to do a careful analysis of the existing system, in order to understand how the new system you propose would differ. This analysis will also consider how people’s positions and tasks will have to change if the new system is put into effect. In general, it involves a detailed study of: The information needs of the organization and all users;The actives, resources, and products or any present information systems;The information systems capabilities required to need the established information needs and user needs.（2）Gather dataIn gathering data, systems analysts use a handful of tools. Most of them not tem ply technical. They include written documents, interviews, questionnaires, observation, and sampling.Written documents: a great deal of what you need is probably available in the form of written documents, and so on. Documents are a good place to start because they tell you how things are or are supposed to be. These tools will also provide leads on people and areas to pursuer further.Interviews: interviews with managers, workers, clients, suppliers, and competitors will also give you insights. Interviews may be structured or unstructured.Questionnaires: questionnaires are useful for getting information for large groups of people when you can’t get around to interviewing everyone. Questionnaires may also yield more information if respondents can be anonymous. In addition, this tool is convenient, is inexpensive, and yields a lot of data. However, people may not return their forms, results can be ambiguous, and with anonymous questionnaires you’ll have no opportunity to follow up.Observation: no doubt you’ve sat in a coffee shop or on a park bench and just alone ―a person is watching‖. This can be a tool for analysis, too. Through observation you can see how people interact with one another and how paper moves through an organization. Observation can be non-participant or participant. If you are a non-participant observer, and people knew they are a participant observer, you may gain more insights by experiencing the conflicts and responsibilities of the people you are working with.（3）Analyze the dataOnce the data is gathered, you need to come to grips with it and analyze it. Many analytical tools, or modeling tools, are available. Modeling tools enables a systems analyst to present graphic representations of a system. Examples are CASE tools,data flow diagrams, systems flow charts, connectivity diagrams, grid charts, decision tables, and object-oriented analysis.For example, in analyzing the current system and preparing data flow diagrams, the systems analyst must also prepare a data dictionary, which is then used and expanded during all remaining phases of the SDLC. A data dictionary defines all the elements that make up the data flow. Among other things, it records what each data element is by name, how long it is, are where it is used, as well as any numerical values assigned to it. This information is usually entered into a data dictionary software program.The Phase: Design the System（4）At the conclusions of the third phase of the SDLC, what should have been created?The objectives of phase 3, systems design, are to do a preliminary design and then a detail and to write a report. In this third phase of the SDLC, you will essentially create a rough draft and then a detail draft of the proposed information system.（5）Do a preliminary designA preliminary design describes the general foundational capabilities of proposed information system. It reviews the system requirements and then considers major components of the system. Usually several alternative systems are considered, and the costs and the benefits of each are evaluated.Some tools that may be used in the preliminary design an the detail design are following:CASE tools: they are software programs that automate various activities of the SDLC in several phases. This screen is from one of their banking system tools. It shows a model for an A TM transaction. The purchaser of the CASE tool would enter details relative to the particular situation. This technology is intended to speed up to the process of developing systems and to improve the quality of the resulting systems.Project management software: it consists of programs used to plan, schedule, a control the people, costs, and resources required to complete a project on time.3 A detail designA detail design describes how a proposed information system will deliver the general capabilities in the preliminary design. The detail design usually considers the following parts of the system, in this order: output requirements, and system controls and backup.(1) Output requirements: the first thing to determine is what you want the system to produce. In this first step, the systems analyst determines what media the appearance or format of the output, such as headings, columns, and menus.(2) Input requirements: once you know the output, you can determine the inputs, here, too, you must define the type of input, such as keyboard or source data entry. You must determine in what form data will be input and how it will be checked for accuracy. You also need to figure out what volume of data the system can be allowed to take in.(3) Storage requirements: using the data dictionary as a quite, you need to define the files and databases in the information system. How will the files be organized? What kind of storage devices will be used? How will they interface with other storage devices inside and outside of the organization? What will be the volume of database activity?(4) Processing and networking requirements, what kind of computer or computers will be used to handle the processing? What kind of operating system and applications software will be used? Will the computer or computers be tied to others in a network? Exactly what operations will be performed on the input data to achieve the desired output information? What kinds of user interface are desired?(5) System controls backup: finally, you need to think about matters of security, privacy, and data accuracy. You need to prevent unauthorized users from breaking into the system, for example, and snooping in private files. You need to devise auditing procedures and to set up specifications for testing the new system. Finally, you need to institute automatic ways of backing up information and storing it else where in case the system fails or is destroyed.4 Develop/Acquire the System（1）What general tasks do systems analysts perform in the fourth phase of the SDLC?Systems development/acquisition, the systems analysts or others in the organization acquire the software, acquire thehardware, and then test the system. This phase begins once management has accepted the report containing the design and has‖green lighted‖the way to development. Depending on the size of the project, this phase will probably involve substantial expenditures of money and time. However, at the end you should have a workable system.（2）Acquire softwareDuring the design stage, the systems analyst may have had to address what is called the ―make-or-buy‖ decision; if not, that decision certainly cannot be avoided now. In the make-or-buy decision, you decide whether you have to create a program –have it custom-written—or buy it. Sometimes programmers decide they can buy an existing software package and modify it rather than write it from scratch.If you decide to create a new program, then the question is whether to use the organization’s own staff programmers or to hair outside contract programmers. Whichever way you go, the task could take months.（3）Acquire hardwareOnce the software has been chosen, the hardware to run it must be acquired or upgraded. It’s possible you will not need to obtain any new hardware. It’s also possible that the new hardware will cost millions of dollars and involve many items: models, and many other devices. The organization may prefer to lease rather than buy some equipment, especially since chip capability was traditionally doubled about every 18 months.（4）Test the systemWith the software and hardware acquired, you can now start testing the system in two stages: first unit testing and then system testing. If CASE tools have been used throughout the SDLC, testing is minimized because any automatically generated program code is more likely to be error free.5 Implement the System（1）What tasks are typically performed in the fifth phase of the SDLC?Whether the new information system involves a few handheld computers, and elaborate telecommunications network, or expensive mainframes, phase 5,systems implementation, with involve some close coordination to make the system not just workable but successful, and people are tainted to use it.6 Maintain the System（1）What two tools are often used in the maintenance phase of the SDLC?Phase 6, systems maintain, adjusts and improves the system by having system audits and periodic evaluations and by making changes based on new conditions.Even with the conversion accomplished and the users trained, the system won’t just run itself. There is a sixth-and never-ending –phase in which the information system must—monitored to ensure that it is effective. Maintenance includes not only keeping the machinery running but also updating and upgrading the system to keep pace with new products, services, customers, government regulations, and other requirements.附件二英汉翻译系统开发阶段随着社会的发展，个人关系管理在日常生活中起的左右显而易见，怎样增强个人管理管理能力，减少管理成本，加强服务水平和个人的竞争力是困扰每一个主管的重要问题之一。
VisualC++ MFC简要介绍毕业设计外文翻译
计算机专业毕业设计外文翻译Visual C++ MFC 简要介绍工学部工学一部专业计算机科学与技术班级学号姓名指导教师负责教师2008年7月Introduction to MFC Programming with Visual C++ Version 6.xby Marshall BrainVisual C++ is much more than a compiler. It is a complete application development environment that, when used as intended, lets you fully exploit the object oriented nature of C++ to create professional Windows applications. In order to take advantage of these features, you need to understand the C++ programming language. If you have never used C++, please turn to the C++ tutorials in the C/C++ Tutorials page for an introduction. You must then understand the Microsoft Foundation Class (MFC) hierarchy. This class hierarchy encapsulates the user interface portion of the Windows API, and makes it significantly easier to create Windows applications in an object oriented way. This hierarchy is available for and compatible with all versions of Windows. The code you create in MFC is extremely portable.These tutorials introduce the fundamental concepts and vocabulary behind MFC and event driven programming. In this tutorial you will enter, compile, and run a simple MFC program using Visual C++. Tutotial 2 provides a detailed explanation of the code used in Tutorial 1. Tutorial 3 discusses MFC controls and their customization. Tutorial 4 covers message maps, which let you handle events in MFC.What is the Microsoft Foundations Class Library?Let's say you want to create a Windows application. You might, for example, need to create a specialized text or drawing editor, or a program that finds files on a large hard disk, or an application that lets a user visualize the interrelationships in a big data set. Where do you begin?A good starting place is the design of the user interface. First, decide what the user should be able to do with the program and then pick a set of user interface objects accordingly. The Windows user interface has a number of standard controls, such as buttons, menus, scroll bars, and lists, that are already familiar to Windows users. With this in mind, the programmer must choose a set of controls and decide how they should be arranged on screen. A time-honored procedure is to make a rough sketch of the proposed user interface (by tradition on a napkin or the back of an envelope) and play with the elements until they feel right. For small projects, or for the early prototyping phase of a larger project, this is sufficient.The next step is to implement the code. When creating a program for any Windowsplatform, the programmer has two choices: C or C++. With C, the programmer codes at the level of the Windows Application Program Interface (API). This interface consists of a collection of hundreds of C functions described in the Window's API Reference books. For Window's NT, the API is typically referred to as the "Win32 API," to distinguish it from the original 16-bit API of lower-level Windows products like Windows 3.1.Microsoft also provides a C++ library that sits on top of any of the Windows APIs and makes the programmer's job easier. Called the Microsoft Foundation Class library (MFC), this library's primary advantage is efficiency. It greatly reduces the amount of code that must be written to create a Windows program. It also provides all the advantages normally found in C++ programming, such as inheritance and encapsulation. MFC is portable, so that, for example, code created under Windows 3.1 can move to Windows NT or Windows 95 very easily. MFC is therefore the preferred method for developing Windows applications and will be used throughout these tutorials.When you use MFC, you write code that creates the necessary user interface controls and customizes their appearance. You also write code that responds when the user manipulates these controls. For example, if the user clicks a button, you want to have code in place that responds appropriately. It is this sort of event-handling code that will form the bulk of any application. Once the application responds correctly to all of the available controls, it is finished.You can see from this discussion that the creation of a Windows program is a straightforward process when using MFC. The goal of these tutorials is to fill in the details and to show the techniques you can use to create professional applications as quickly as possible. The Visual C++ application development environment is specifically tuned to MFC, so by learning MFC and Visual C++ together you can significantly increase your power as an application developer.Windows V ocabularyThe vocabulary used to talk about user interface features and software development in Windows is basic but unique. Here we review a few definitions to make discussion easier for those who are new to the environment.Windows applications use several standard user controls:Static text labelsPush buttonsList boxesCombo boxes (a more advanced form of list)Radio boxesCheck boxesEditable text areas (single and multi-line)Scroll barsYou can create these controls either in code or through a "resource editor" that can create dialogs and the controls inside of them. In this set of tutorials we will examine how to create them in code. See the tutorials on the AppWizard and ClassWizard for an introduction to the resource editor for dialogs.Windows supports several types of application windows. A typical application will live inside a "frame window". A frame window is a fully featured main window that the user can re-size, minimize, maximize to fill the screen, and so on. Windows also supports two types of dialog boxes: modal and modeless. A modal dialog box, once on the screen, blocks input to the rest of the application until it is answered. A modeless dialog box can appear at the same time as the application and seems to "float above" it to keep from being overlaid.Most simple Windows applications use a Single Document Interface, or SDI, frame. The Clock, PIF editor, and Notepad are examples of SDI applications. Windows also provides an organizing scheme called the Multiple Document Interface, or MDI for more complicated applications. The MDI system allows the user to view multiple documents at the same time within a single instance of an application. For example, a text editor might allow the user to open multiple files simultaneously. When implemented with MDI, the application presents a large application window that can hold multiple sub-windows, each containing a document. The single main menu is held by the main application window and it applies to the top-most window held within the MDI frame. Individual windows can be iconified or expanded as desired within the MDI frame, or the entire MDI frame can be minimized into a single icon on the desktop. The MDI interface gives the impression of a second desktop out on the desktop, and it goes a long way towards organizing and removing window clutter.Each application that you create will use its own unique set of controls, its own menu structure, and its own dialog boxes. A great deal of the effort that goes into creating anygood application interface lies in the choice and organization of these interface objects. Visual C++, along with its resource editors, makes the creation and customization of these interface objects extremely easy.Event-driven Software and V ocabularyAll window-based GUIs contain the same basic elements and all operate in the same way. On screen the user sees a group of windows, each of which contains controls, icons, objects and such that are manipulated with the mouse or the keyboard. The interface objects seen by the user are the same from system to system: push buttons, scroll bars, icons, dialog boxes, pull down menus, etc. These interface objects all work the same way, although some have minor differences in their "look and feel." For example, scroll bars look slightly different as you move from Windows to the Mac to Motif, but they all do the same thing.From a programmer's standpoint, the systems are all similar in concept, although they differ radically in their specifics. To create a GUI program, the programmer first puts all of the needed user interface controls into a window. For example, if the programmer is trying to create a simple program such as a Fahrenheit to Celsius converter, then the programmer selects user interface objects appropriate to the task and displays them on screen. In this example, the programmer might let the user enter a temperature in an editable text area, display the converted temperature in another un-editable text area, and let the user exit the program by clicking on a push-button labeled "quit".As the user manipulates the application's controls, the program must respond appropriately. The responses are determined by the user's actions on the different controls using the mouse and the keyboard. Each user interface object on the screen will respond to events differently. For example, if the user clicks the Quit button, the button must update the screen appropriately, highlighting itself as necessary. Then the program must respond by quitting. Normally the button manages its appearance itself, and the program in some way receives a message from the button that says, "The quit button was pressed. Do something about it." The program responds by exiting.Windows follows this same general pattern. In a typical application you will create a main window and place inside it different user interface controls. These controls are often referred to as child windows-each control is like a smaller and more specialized sub-window inside the main application window. As the application programmer, youmanipulate the controls by sending messages via function calls, and they respond to user actions by sending messages back to your code.If you have never done any "event-driven" programming, then all of this may seem foreign to you. However, the event-driven style of programming is easy to understand. The exact details depend on the system and the level at which you are interfacing with it, but the basic concepts are similar. In an event-driven interface, the application paints several (or many) user interface objects such as buttons, text areas, and menus onto the screen. Now the application waits-typically in a piece of code called an event loop-for the user to do something. The user can do anything to any of the objects on screen using either the mouse or the keyboard. The user might click one of the buttons, for example. The mouse click is called an event. Event driven systems define events for user actions such as mouse clicks and keystrokes, as well as for system activities such as screen updating.At the lowest level of abstraction, you have to respond to each event in a fair amount of detail. This is the case when you are writing normal C code directly to the API. In such a scenario, you receive the mouse-click event in some sort of structure. Code in your event loop looks at different fields in the structure, determines which user interface object was affected, perhaps highlights the object in some way to give the user visual feedback, and then performs the appropriate action for that object and event. When there are many objects on the screen the application becomes very large. It can take quite a bit of code simply to figure out which object was clicked and what to do about it.Fortunately, you can work at a much higher level of abstraction. In MFC, almost all these low-level implementation details are handled for you. If you want to place a user interface object on the screen, you create it with two lines of code. If the user clicks on a button, the button does everything needed to update its appearance on the screen and then calls a pre-arranged function in your program. This function contains the code that implements the appropriate action for the button. MFC handles all the details for you: You create the button and tell it about a specific handler function, and it calls your function when the user presses it. Tutorial 4 shows you how to handle events using message maps An ExampleOne of the best ways to begin understanding the structure and style of a typical MFC program is to enter, compile, and run a small example. The listing below contains a simple "hello world" program. If this is the first time you've seen this sort of program, it probablywill not make a lot of sense initially. Don't worry about that. We will examine the code in detail in the next tutorial. For now, the goal is to use the Visual C++ environment to create, compile and execute this simple program.//hello.cpp#include <afxwin.h>// Declare the application classclass CHelloApp : public CWinApp{public:virtual BOOL InitInstance();};// Create an instance of the application classCHelloApp HelloApp;// Declare the main window classclass CHelloWindow : public CFrameWnd{CStatic* cs;public:CHelloWindow();};// The InitInstance function is called each// time the application first executes.BOOL CHelloApp::InitInstance(){m_pMainWnd = new CHelloWindow();m_pMainWnd->ShowWindow(m_nCmdShow);m_pMainWnd->UpdateWindow();return TRUE;}// The constructor for the window classCHelloWindow::CHelloWindow(){// Create the window itselfCreate(NULL,"Hello World!",WS_OVERLAPPEDWINDOW,CRect(0,0,200,200));// Create a static labelcs = new CStatic();cs->Create("hello world",WS_CHILD|WS_VISIBLE|SS_CENTER,CRect(50,80,150,150),this);}This small program does three things. First, it creates an "application object." Every MFC program you write will have a single application object that handles the initialization details of MFC and Windows. Next, the application creates a single window on the screen to act as the main application window. Finally, inside that window the application creates a single static text label containing the words "hello world". We will look at this program in detail in the next tutorial to gain a complete understanding of its structure.The steps necessary to enter and compile this program are straightforward. If you have not yet installed Visual C++ on your machine, do so now. You will have the option of creating standard and custom installations. For the purposes of these tutorials a standard installation is suitable and after answering two or three simple questions the rest of the installation is quick and painless.Start VC++ by double clicking on its icon in the Visual C++ group of the Program Manager. If you have just installed the product, you will see an empty window with a menu bar. If VC++ has been used before on this machine, it is possible for it to come up in several different states because VC++ remembers and automatically reopens the project and files in use the last time it exited. What we want right now is a state where it has no project or code loaded. If the program starts with a dialog that says it was unable to find a certain file, clear the dialog by clicking the "No" button. Go to the Window menu and select the Close All option if it is available. Go to the File menu and select the Close option if it is available to close any remaining windows. Now you are at the proper starting point.If you have just installed the package, you will see a window that looks something like this:This screen can be rather intimidating the first time you see it. To eliminate some ofthe intimidation, click on the lower of the two "x" buttons () that you see in the upper right hand corner of the screen if it is available. This action will let you close the "InfoViewer Topic" window. If you want to get rid of the InfoViewer toolbar as well, you can drag it so it docks somewhere along the side of the window, or close it and later get it back by choosing the Customize option in the Tools menu.What you see now is "normal". Along the top is the menu bar and several toolbars. Along the left side are all of the topics available from the on-line book collection (you might want to explore by double clicking on several of the items you see there - the collection of information found in the on-line books is gigantic). Along the bottom is a status window where various messages will be displayed.Now what? What you would like to do is type in the above program, compile it and run it. Before you start, switch to the File Manager (or the MS-DOS prompt) and make sure your drive has at least five megabytes of free space available. Then take the following steps.Creating a Project and Compiling the CodeIn order to compile any code in Visual C++, you have to create a project. With a very small program like this the project seems like overkill, but in any real program the projectconcept is quite useful. A project holds three different types of information: It remembers all of the source code files that combine together to create one executable. In this simple example, the file HELLO.CPP will be the only source file, but in larger applications you often break the code up into several different files to make it easier to understand (and also to make it possible for several people to work on it simultaneously). The project maintains a list of the different source files and compiles all of them as necessary each time you want to create a new executable.It remembers compiler and linker options particular to this specific application. For example, it remembers which libraries to link into the executable, whether or not you want to use pre-compiled headers, and so on.It remembers what type of project you wish to build: a console application, a windows application, etc.If you are familiar with makefiles, then it is easy to think of a project as a machine-generated makefile that has a very easy-to-understand user interface to manipulate it. For now we will create a very simple project file and use it to compile HELLO.CPP.To create a new project for HELLO.CPP, choose the New option in the File menu. Under the Projects tab, highlight Win32 Application. In the Location field type an appropriate path name or click the Browse button. Type the word "hello" in for the project name, and you will see that word echoed in the Location field as well. Click the OK button. In the next window, use the default selection "An empty project", click "Finish", then click "OK" once more in the next window. Notice there is an option for the typical "Hello World" application, however it skips a few important steps you are about to take. Visual C++ will create a new subdirectory named HELLO and place the project files named HELLO.OPT, HELLO.NCB, HELLO.DSP, and HELLO.DSW in that directory. If you quit and later want to reopen the project, double-click on HELLO.DSW.The area along the left side of the screen will now change so that three tabs are available. The InfoView tab is still there, but there is now also a ClassView and a FileView tab. The ClassView tab will show you a list of all of the classes in your application and the FileView tab gives you a list of all of the files in the project.Now it is time to type in the code for the program. In the File menu select the New option to create a new editor window. In the dialog that appears, make sure the Files tab isactive and request a "C++ Source File". Make sure the "Add to Project" option is checked for Project "hello", and enter "hello" for "File name". Visual C++ comes with its own intelligent C++ editor, and you will use it to enter the program shown above. Type (copy/paste) the code in the listing into the editor window. You will find that the editor automatically colors different pieces of text such as comments, key words, string literals, and so on. If you want to change the colors or turn the coloring off, go to the Options option in the Tools menu, choose the Format tab and select the Source Windows option from the left hand list. If there is some aspect of the editor that displeases you, you may be able to change it using the Editor tab of the Options dialog.After you have finished entering the code, save the file by selecting the Save option in the File menu. Save it to a file named HELLO.CPP in the new directory Visual C++ created.In the area on the left side of the screen, click the FileView tab and expand the tree on the icon labeled "hello files", then expand the tree on the folder icon labeled "Source Files". You will see the file named HELLO.CPP. Click on the ClassView tab and expand the "hello classes" tree and you will see the classes in the application. You can remove a file from a project at any time by going to the FileView, clicking the file, and pressing the delete button.Finally, you must now tell the project to use the MFC library. If you omit this step the project will not link properly, and the error messages that the linker produces will not help one bit. Choose the Settings option in the Project menu. Make sure that the General tab is selected in the tab at the top of the dialog that appears. In the Microsoft Foundation Classes combo box, choose the third option: "Use MFC in a Shared DLL." Then close the dialog.Having created the project file and adjusted the settings, you are ready to compile the HELLO.CPP program. In the Build menu you will find three different compile options: Compile HELLO.CPP (only available if the text window for HELLO.CPP has focus) Build HELLO.EXERebuild AllThe first option simply compiles the source file listed and forms the object file for it. This option does not perform a link, so it is useful only for quickly compiling a file to check for errors. The second option compiles all of the source files in the project that have been modified since the last build, and then links them to form an executable. The thirdoption recompiles all of the source files in the project and relinks them. It is a "compile and link from scratch" option that is useful after you change certain compiler options or move to a different platform.In this case, choose the Build HELLO.EXE option in the Build menu to compile and link the code. Visual C++ will create a new subdirectory named Debug and place the executable named HELLO.EXE in that new subdirectory. This subdirectory holds all disposable (easily recreated) files generated by the compiler, so you can delete this directory when you run short on disk space without fear of losing anything important.If you see compiler errors, simply double click on the error message in the output window. The editor will take you to that error. Compare your code against the code above and fix the problem. If you see a mass of linker errors, it probably means that you specified the project type incorrectly in the dialog used to create the project. You may want to simply delete your new directory and recreate it again following the instructions given above exactly.To execute the program, choose the Execute HELLO.EXE option in the Build menu.A window appears with the words "hello world". The window itself has the usual decorations: a title bar, re-size areas, minimize and maximize buttons, and so on. Inside the window is a static label displaying the words "hello world". Note that the program is complete. You can move the window, re-size it, minimize it, and cover and uncover it with other windows. With a very small amount of code you have created a complete Window application. This is one of the many advantages of using MFC. All the details are handled elsewhere.Visual C++ MFC 简要介绍原著：Marshall Brain Visual C++ 不仅仅是一个编译器。
毕业设计论文外文文献翻译计算机科学与技术微软VisualStudio中英文对照
外文文献翻译（2012届）学生姓名学号********专业班级计算机科学与技术08-5班指导教师微软Visual Studio1微软Visual StudioVisual Studio 是微软公司推出的开发环境，Visual Studio可以用来创建Windows平台下的Windows应用程序和网络应用程序，也可以用来创建网络服务、智能设备应用程序和Office 插件。
Visual Studio是一个来自微软的集成开发环境IDE（inteqrated development environment），它可以用来开发由微软视窗，视窗手机，Windows CE、.NET框架、.NET精简框架和微软的Silverlight支持的控制台和图形用户界面的应用程序以及Windows窗体应用程序，网站，Web应用程序和网络服务中的本地代码连同托管代码。
Visual Studio包含一个由智能感知和代码重构支持的代码编辑器。
集成的调试工作既作为一个源代码级调试器又可以作为一台机器级调试器。
其他内置工具包括一个窗体设计的GUI应用程序，网页设计师，类设计师，数据库架构设计师。
它有几乎各个层面的插件增强功能，包括增加对支持源代码控制系统（如Subversion和Visual SourceSafe）并添加新的工具集设计和可视化编辑器，如特定于域的语言或用于其他方面的软件开发生命周期的工具（例如Team Foundation Server的客户端：团队资源管理器）。
Visual Studio支持不同的编程语言的服务方式的语言，它允许代码编辑器和调试器（在不同程度上）支持几乎所有的编程语言，提供了一个语言特定服务的存在。
内置的语言中包括C/C + +中（通过Visual C++）,（通过Visual ），C＃中（通过Visual C＃）和F＃（作为Visual Studio 2010），为支持其他语言，如M,Python,和Ruby等，可通过安装单独的语言服务。
计算机相关专业毕业设计外文翻译--移动设备的应用平台—J2ME简介
附件1：外文资料翻译译文移动设备的应用平台—J2ME简介1.什么是J2ME:J2ME(Java 2 Micro Edition)是Java 2的一个组成部分，它与J2SE、J2EE并称。
根据Sun的定义：J2ME是一种高度优化的Java运行环境，主要针对消费类电子设备的，例如蜂窝电话和可视电话、数字机顶盒、汽车导航系统等等。
J2ME 技术在1999年的JavaOne Developer Conference大会上正式推出，它将Java语言的与平台无关的特性移植到小型电子设备上,允许移动无线设备之间共享应用程序。
J2ME在设计其规格的时候，遵循着对于各种不同的装置而造出一个单一的开发系统是没有意义的事」这个基本原则。
于是J2ME 先将所有的嵌入式装置大体上区分为两种:一种是运算功能有限、电力供应也有限的嵌入式装置(比方说PDA 、手机)；另外一种则是运算能力相对较佳、并请在电力供应上相对比较充足的嵌入式装置(比方说冷气机、电冰箱、电视机上盒(set-top box))。
因为这两种型态的嵌入式装置，所以Java 引入了一个叫做Configuration 的概念，然后把上述运算功能有限、电力有限的嵌入式装置定义Connected Limited Device Configuration(CLDC)规格之中；而另外一种装置则规范为Connected Device Configuration(CDC)规格。
也就是说,J2ME 先把所有的嵌入式装置利Configuration 的概念区隔成两种抽象的型态。
其实在这里大家可以把Configuration 当作是J2ME 对于两种类型嵌入式装置的规格，而这些规格之中定义了这些装置至少要符合的运算能力、供电能力、记忆体大小等规范，同时也定了一组在这些装置上执行的Java 程序所能使用的类别函式库、这些规范之中所定义的类别函式库为Java 标准核心类别函式库的子集合以及与该型态装置特性相符的扩充类别函式库。
计算机专业毕业设计外文翻译--网站建立的五要素
Five essential elements that the website set up Though the network is total to enter overcast appearance currently, but the power head of the business enterprise construction website back anti- increase. A lot of have farseeing of the business enterprise has already used from the network of the convenience is sexy to arrive construction one self’s website of inevitable. At present is the bran acre that burns money, the concept website drops into in succession of day is exactly also the entity business enterprise that has real strength to get involved a network of hour. But, when the business enterprise decision assurance want to do a website of time, but usually commence from nowhere, don't know need to be throw in how much , need to be usher in what talented person. Under the circumstance of this kind of innumerable in heart, general business enterprise usually according to the mode of the business enterprise publicity material, under the suggestion of the network company or IT technical personnel, the construction becomes the business enterprise website that goes through a format. This kind of business enterprise website that goes through a format, also have it five essential elements: The business enterprise introduction, the contact way, the product(service) introduction, message board, forum. The value of this kind of business enterprise website, the equal to per origin electronics version business enterprise publicity volume, turns over while being provided for interested in customer to need. Therefore, a lot of business enterprises think, throw in several 10000 dollars to do a didn't how much person visit of the website have unworthy. BE a network particularly currently at the time that heat fade away, the general business enterprise can't even consider to throw in several hundred top the ten million imitate the large website of the pure concept.So, how make sure the fixed position that the business enterprise constructs a website?The key figures make policy to the website a real realization from the business enterprise, what is the most decisive decision factor? Isn't the network company or the IT technical personnel's level, is not the funds devotion of the business enterprise either how much, is a website whole plan ability. A lot of business enterprise superstition IT techniques, think as long as invite a professional talented person of IT of arrive the high point, can set up a website. The technical personnel of the IT also is much conceited, the condition of the market also anticipates a rising continuously. Quite good, set up a website not difficult. As long as there is funds, time and condition, anyone’s all can be CEO, CFO, the COO etc. Had no more easy but cheap than network life and the business stage up to now from the thou. This also is why will appear so many websites of cause. But, regardless the technique level is much high, it is just means but isn't a purpose. Have no business enterprise need, technique useless.On the other hand, the business enterprise devotion funds also doesn't necessarily can attain result. There has been currently several 100 up under the circumstance of the website of the ten million, how much a new website really not easy cause people an attention. Regardless website the oneself thinks the meaning is how important, people have already no longer believed the tears and battle cry. People get to the Internet, end is for look for real to oneself useful resources. The resources just is a website to exist of unique have a foothold it originally. Resources of how much decision the size of thewebsite value, this is the truth that the network just knows through the rains and winds of this several years. Depended on an advertisement to try to gain an eyeball to own quantity before, click a rate, popularity etc. the concept has already fall into disfavor, take but the generation registered the customer number, visiting again a rate(turn head a rate), the source information quantity with can participate degree etc. standard. Not only is a risk only investment the house concern these, the website constructor and the plan also should even concern these.Five essential elements of the website construction : Purpose, resources, technique, object, result. The purpose is a need, is the initial problem that the website owns and lets design to understand. The purpose have at present of with long-term of, have public of with implicit of, have direct of with indirect of, have main of with from belong to of, is viable with not viable etc. The purpose relates to the aim or the creativity of the website directly. The creativity of the website is the soul place of the website. Have no creative website like have no the hull of soul. The concept of the resources is very extensive, not the simplicity point the amount of information that the oneself can provide. The funds is the most important composition in the resources. The common saying say: See the vegetables have a meal, measuring form dress. To website, this is the key particularly. The network is a pasta, want to crumple what kind be what kind; the network is a bottomless pit again, how much can burn down. Therefore, the network the earnings mode is the website constructor should be clear early of a debt. For the very first time preparation devotion how much, prepare to support a funds annually how much, provide how much human resource, short date profit and loss the balance point and the long-term earnings target etc. Contents-manpower-funds the threes are closely related. All want to weigh the manpower and the funds resources that can adjust a degree while designing each column eyes in the consideration website. Explicit the purpose and resources be a choice immediately after what technique level. BE the static state a page still a dynamic state page for example, whether the adoption database, the beautiful work result has high and low request, the renewal speed rate of speed and the maintenance way JIAN3 FAN2's etc. Will consider the website service object to participate degree in using convenience. Be also the most important finally, is hope the website attain what result, and how attain this result.The main page is the square one of the website design. Many persons also think the website design are a main page design, the main page level high and low representative website level is high and low. Really such to some extent, so the style, the color layout, the column eyes design, writing of the main page expresses the place that etc. becomes a website to produce a controversy most easily. The so-called sees, a wise man sees ,this top has no everyone forever consistently satisfied of opinion, more temperament styles that is a body to design directly now. Along with to website cognitive transformation, the style of the main page is also transformation usually. But, the main page should be understand to tell customer without any error its purpose, this is affirmative. Now a lot of websites is a particularly large website, all in succession outstanding it owns in the top of the main page of resources, browse with the automatic and more recent contents attraction customer. Therefore, these main pages all imply the dynamic state renewal contents of, then belong to a dynamic state web page technique. And, want generally in consideration of the tasteof the customer(object), arrange in the contents up set up with meticulous care, attain the best result by period. The main page design has two kinds of main trends: Pursue beautiful result(static state) of appearance with pursue a contents abundant result(dynamic state), the former in keeping with contents not much of business enterprise website, the latter suits the comprehensive website that the contents enrich. But some function websites, usually chase the most function outstanding in the main page center, if search the engine and large database.The column purpose the assurance is the website inner part structure of key. Usually forum, message board, the concerning us, website navigate, declare, register area etc. the basic column eyes all put in the next in importance position chain to connect into. The news, main function, main contents, the renewal contents hint etc. puts in the refreshing position. The news and renewal are a website to order, it make, is one of the main meanness that the attraction turns head a rate, is also an essential website necessary of. In browse the eyes, the vitality of the website now of body is here.The website contents cent the function and information two major type. Function have: search engine, the database index, stand to order to navigate, electronic commerce, community, submit manuscript, the self-help web page(free and main page), register, network office etc. The information containment all levels writing page, the data database, and the related chain connect etc. The basis website purpose make sure outstanding what contents, and enrichment and the renewal contents of the technique means and form.The customer(object) community also has important influence to the website design. Face an experienced professional of network for example with face general common customer, its technique carries out a way different, to "usage convenience" the comprehension of this phrase, two community is also different.What is the marking of[with] the website planning success? Be click a rate, popularity, register a number, turn head a rate and lead of consent, great ,contents of customer of abundant, use of convenience, operate of smooth, invest the favor of the house? Also being also incompletely. Successful website should be comprehend to set up the station purpose with accuracy, adjust a limited resources of one degree adequately, fittingly usage suitable technique, serve the usage object expediently, attain expectation result in time. Why want to say convenience with in time? Because network the biggest advantage be fast with the convenience, if the website compares other paths to have no forerunner, even can attain the expectation result a mill- also is nonsense.Construct a website not difficult, is the maintenance and the development that sets up the empress website seldom. Regardless how creativity is novel, the website continues to develop to return a root to still depend on a resources exactly, depending on forever an information total amount of lead the one step, otherwise will be very quickly replace by person. Website depended on a creativity to become famous with one action, its creativity drive after person's mimicry, very quickly the example replace by person is all like that.So, website at set up after, how support with the development?1. The persistence is own special features. The special features is the body of the purpose now, the persistence special features is the purpose that the persistence sets up a station. Usually the transformation special features is disaster to website, being equal tore- construct a new website continuously, how much efforts all would the form notbecome a backlog but throw to the winds. And the manpower funds waste very greatly.2. Concentration the most information’s. Must concentrate all related information’s with maximum limit in own realm. Website like gather city, always merchandise the most places can draw on the most persons. Adopt the whole way collections and display the contents that the website enrich under the possible condition, this principle can never be dated.3. Keep a technical forerunner. As long as the condition allow, must have the technique strength to carry on the technique reformation and exaltation to the website. The website beginning sets up a hair building just, need to be continuously perfect with the correction, reform with exaltation. If don't go together with other to keep to even surmount synchronously on the technique, the website is very quick and then will fade out history stage.4. Control the need of the customer. The customer need is the problem that puts in the first to consider. Among them participate is the most important need of customer. The customer can announce a speech, message, put forward animadversion and construct an opinion general to just participate. Whether website satisfies the need of the customer or not, its participating degree is a main marking.5. Consciousness tracked to run before. The magic power of the network is it continuously creative with surmount. The network constructor must track to flow out continuously to run before consciousness now, and reflect it to own website in time in. This will never be what pursue one astonishing, gain notoriety by shocking statement of result, but the inevitable request that maintenance leads a position.In fine, is the website beginning to set up regardless to still develop over a long period of time, five essential elements all from beginning to end carry through among them. Among them decisive be still a resources-funds, talented person, information, andall participants pay the effort and the strenuous effort of.网站建立的五要素尽管目前网络总体进入低迷状态，但企业建设网站的势头却不退反增。
计算机科学与技术Java垃圾收集器中英文对照外文翻译文献
中英文资料中英文资料外文翻译文献原文：How a garbage collector works of Java LanguageIf you come from a programming language where allocating objects on the heap is expensive, you may naturally assume that Java’s scheme of allocating everything (except primitives) on the heap is also expensive. However, it turns out that the garbage collector can have a significant impact on increasing the speed of object creation. This might sound a bit odd at first—that storage release affects storage allocation—but it’s the way some JVMs work, and it means that allocating storage for heap objects in Java can be nearly as fast as creating storage on the stack in other languages.For example, you can think of the C++ heap as a yard where each stakes out its own piece of turf object. This real estate can become abandoned sometime later and must be reused. In some JVMs, the Java heap is quite different; it’s more like a conveyor belt that moves forwardevery time you allocate a new object. This means that object storage allocation is remarkab ly rapid. The “heap pointer” is simply moved forward into virgin territory, so it’s effectively the same as C++’s stack allocation. (Of course, there’s a little extra overhead for bookkeeping, but it’s nothing like searching for storage.)You might observ e that the heap isn’t in fact a conveyor belt, and if you treat it that way, you’ll start paging memory—moving it on and off disk, so that you can appear to have more memory than you actually do. Paging significantly impacts performance. Eventually, after you create enough objects, you’ll run out of memory. The trick is that the garbage collector steps in, and while it collects the garbage it compacts all the objects in the heap so that you’ve effectively moved the “heap pointer” closer to the beginning of the conveyor belt and farther away from a page fault. The garbage collector rearranges things and makes it possible for the high-speed, infinite-free-heap model to be used while allocating storage.To understand garbage collection in Java, it’s helpful le arn how garbage-collection schemes work in other systems. A simple but slow garbage-collection technique is called reference counting. This means that each object contains a reference counter, and every time a reference is attached to that object, the reference count is increased. Every time a reference goes out of scope or is set to null, the reference count isdecreased. Thus, managing reference counts is a small but constant overhead that happens throughout the lifetime of your program. The garbage collector moves through the entire list of objects, and when it finds one with a reference count of zero it releases that storage (however, reference counting schemes often release an object as soon as the count goes to zero). The one drawback is that if objects circularly refer to each other they can have nonzero reference counts while still being garbage. Locating such self-referential groups requires significant extra work for the garbage collector. Reference counting is commonly used to explain one kind of g arbage collection, but it doesn’t seem to be used in any JVM implementations.In faster schemes, garbage collection is not based on reference counting. Instead, it is based on the idea that any non-dead object must ultimately be traceable back to a reference that lives either on the stack or in static storage. The chain might go through several layers of objects. Thus, if you start in the stack and in the static storage area and walk through all the references, you’ll find all the live objects. For each reference that you find, you must trace into the object that it points to and then follow all the references in that object, tracing into the objects they point to, etc., until you’ve moved through the entire Web that originated with the reference on the stack or in static storage. Each object that you move through must still be alive. Note that there is no problem withdetached self-referential groups—these are simply not found, and are therefore automatically garbage.In the approach described here, the JVM uses an adaptive garbage-collection scheme, and what it does with the live objects that it locates depends on the variant currently being used. One of these variants is stop-and-copy. This means that—for reasons that will become apparent—the program is first stopped (this is not a background collection scheme). Then, each live object is copied from one heap to another, leaving behind all the garbage. In addition, as the objects are copied into the new heap, they are packed end-to-end, thus compacting the new heap (and allowing new storage to simply be reeled off the end as previously described).Of course, when an object is moved from one place to another, all references that point at the object must be changed. The reference that goes from the heap or the static storage area to the object can be changed right away, but there can be other references pointing to this object Initialization & Cleanup that will be encountered later during the “walk.” These are fixed up as they are found (you could imagine a table that maps old addresses to new ones).There are two issues that make these so-called “copy collectors” inefficient. The first is the idea that you have two heaps and you slosh all the memory back and forth between these two separate heaps,maintaining twice as much memory as you actually need. Some JVMs deal with this by allocating the heap in chunks as needed and simply copying from one chunk to another.The second issue is the copying process itself. Once your program becomes stable, it might be generating little or no garbage. Despite that, a copy collector will still copy all the memory from one place to another, which is wasteful. To prevent this, some JVMs detect that no new garbage is being generated and switch to a different scheme (this is the “adaptive” part). This other scheme is called mark-and-sweep, and it’s what earlier versions of Sun’s JVM used all the time. For general use, mark-and-sweep is fairly slow, but when you know you’re generating little or no garbage, it’s fast. Mark-and-sweep follows the same logic of starting from the stack and static storage, and tracing through all the references to find live objects.However, each time it finds a live object, that object is marked by setting a flag in it, but the object isn’t collected yet.Only when the marking process is finished does the sweep occur. During the sweep, the dead objects are released. However, no copying happens, so if the collector chooses to compact a fragmented heap, it does so by shuffling objects around. “Stop-and-copy”refers to the idea that this type of garbage collection is not done in the background; Instead, the program is stopped while the garbage collection occurs. In the Sun literature you’llfind many references to garbage collection as a low-priority background process, but it turns out that the garbage collection was not implemented that way in earlier versions of the Sun JVM. Instead, the Sun garbage collector stopped the program when memory got low. Mark-and-sweep also requires that the program be stopped.As previously mentioned, in the JVM described here memory is allocated in big blocks. If you allocate a large object, it gets its own block. Strict stop-and-copy requires copying every live object from the source heap to a new heap before you can free the old one, which translates to lots of memory. With blocks, the garbage collection can typically copy objects to dead blocks as it collects. Each block has a generation count to keep track of whether it’s alive. In the normal case, only the blocks created since the last garbage collection are compacted; all other blocks get their generation count bumped if they have been referenced from somewhere. This handles the normal case of lots of short-lived temporary objects. Periodically, a full sweep is made—large objects are still not copied (they just get their generation count bumped), and blocks containing small objects are copied and compacted.The JVM monitors the efficiency of garbage collection and if it becomes a waste of time because all objects are long-lived, then it switches to mark-and sweep. Similarly, the JVM keeps track of how successful mark-and-sweep is, and if the heap starts to becomefragmented, it switches back to stop-and-copy. This is where the “adaptive” part comes in, so you end up with a mouthful: “Adaptive generational stop-and-copy mark-and sweep.”There are a number of additional speedups possible in a JVM. An especially important one involves the operation of the loader and what is called a just-in-time (JIT) compiler. A JIT compiler partially or fully converts a program into native machine code so that it doesn’t need to be interpreted by the JVM and thus runs much faster. When a class must be loaded (typically, the first time you want to create an object of that class), the .class file is located, and the byte codes for that class are brought into memory. At this point, one approach is to simply JIT compile all the code, but this has two drawbacks: It takes a little more time, which, compounded throughout the life of the program, can add up; and it increases the size of the executable (byte codes are significantly more compact than expanded JIT code), and this might cause paging, which definitely slows down a program. An alternative approach is lazy evaluation, which means that the code is not JIT compiled until necessary. Thus, code that never gets executed might never be JIT compiled. The Java Hotspot technologies in recent JDKs take a similar approach by increasingly optimizing a piece of code each time it is executed, so the more the code is executed, the faster it gets.译文：Java垃圾收集器的工作方式如果你学下过一种因为在堆里分配对象所以开销过大的编程语言，很自然你可能会假定Java 在堆里为每一样东西（除了primitives）分配内存资源的机制开销也会很大。
计算机毕业设计外文翻译-- 电路交换网与vb调用数据库
即使美国拥有移动电话的所有权，但是在应用上欧洲要远远超过美国的。原因之一就是整个欧洲拥有相同的简单系统。然而更多的是由于美国和欧洲的基本电话数量不同。在美国移动电话和固定电话是共用的，因此对于用户没有办法区分(212)234-5678到底是固定电话(拨打是便宜的或者是免费的)还是移动电话(拨打是昂贵的)。为了使人们从使用电话中获益，电话公司决定为引入呼叫而花自己的钱制造移动电话。结果导致，很多人怕由于呼叫而收到一大笔帐单而不愿意买移动电话。在欧洲移动电话有特殊的区号(如800,900之类的数字)，所以它很快就得到了认可。因而在一般的“叫方付费”的原则在欧洲也被应用于移动电话了(除国际电话分开收费外)。
毕业设计(论文)外文资料翻译
专业班级：计算机科学与技术
外文来源一：网络文摘<<源码天空>>
外文来源二：
指导教师评语：
签名：
切换电路的连接设置的结果是保留了从发送端到接收端的包所通过的线路带宽。其它的特性这一就是所有的包都沿同一个线路意味着如果包传输超过了时序那它将不能到达接收端.由于没有路径用来进行包交换，所以要想不同的包沿不同的路径传送就是能依靠网络的条件了。这样包即便是超过了时序它们也有可能到达的。
计算机毕业设计外文翻译---数据仓库
DATA WAREHOUSEData warehousing provides architectures and tools for business executives to systematically organize, understand, and use their data to make strategic decisions. A large number of organizations have found that data warehouse systems are valuable tools in today's competitive, fast evolving world. In the last several years, many firms have spent millions of dollars in building enterprise-wide data warehouses. Many people feel that with competition mounting in every industry, data warehousing is the latest must-have marketing weapon —— a way to keep customers by learning more about their needs.“So", you may ask, full of intrigue, “what exactly is a data warehouse?"Data warehouses have been defined in many ways, making it difficult to formulate a rigorous definition. Loosely speaking, a data warehouse refers to a database that is maintained separately from an organization's operational databases. Data warehouse systems allow for the integration of a variety of application systems. They support information processing by providing a solid platform of consolidated, historical data for analysis.According to W. H. Inmon, a leading architect in the construction of data warehouse systems, “a data warehouse is a subject-oriented, integrated, time-variant, and nonvolatile collection of data in support of management's decision making process." This short, but comprehensive definition presents the major features of a data warehouse. The four keywords, subject-oriented, integrated, time-variant, and nonvolatile, distinguish data warehouses from other data repository systems, such as relational database systems, transaction processing systems, and file systems. Let's take a closer look at each of these key features.(1)Subject-oriented: A data warehouse is organized around major subjects, such as customer, vendor, product, and sales. Rather than concentrating on the day-to-day operations and transaction processing of an organization, a data warehouse focuses on the modeling and analysis of data for decision makers. Hence, data warehouses typically provide a simple and concise view around particular subject issues by excluding data that are not useful in the decision support process.(2)Integrated: A data warehouse is usually constructed by integrating multiple heterogeneous sources, such as relational databases, flat files, and on-line transaction records. Data cleaning and data integration techniques are applied to ensure consistency in naming conventions, encoding structures, attribute measures, and so on..(3)Time-variant: Data are stored to provide information from a historical perspective (e.g., the past 5-10 years). Every key structure in the data warehouse contains, either implicitly or explicitly, an element of time.(4)Nonvolatile: A data warehouse is always a physically separate store of data transformed from the application data found in the operational environment. Due to this separation, a data warehouse does not require transaction processing, recovery, and concurrency control mechanisms. It usually requires only two operations in data accessing: initial loading of data and access of data..In sum, a data warehouse is a semantically consistent data store that serves as a physical implementation of a decision support data model and stores the information on which an enterprise needs to make strategic decisions. A data warehouse is also often viewed as an architecture, constructed by integrating data from multiple heterogeneous sources to support structured and/or ad hoc queries, analytical reporting, and decision making.“OK", you now ask, “what, then, is data warehousing?"Based on the above, we view data warehousing as the process of constructing and using data warehouses. The construction of a data warehouse requires data integration, data cleaning, and data consolidation. The utilization of a data warehouse often necessitates a collection of decision support technologies. This allows “knowledge workers" (e.g., managers, analysts, and executives) to use the warehouse to quickly and conveniently obtain an overview of the data, and to make sound decisionsbased on information in the warehouse. Some authors use the term “data warehousing" to refer only to the process of data warehouse construction, while the term warehouse DBMS is used to refer to the management and utilization of data warehouses. We will not make this distinction here.“How are organizations using the information from data warehouses?" Many organizations are using this information to support business decision making activities, including:(1) increasing customer focus, which includes the analysis of customer buying patterns (such as buying preference, buying time, budget cycles, and appetites for spending).(2) repositioning products and managing product portfolios by comparing the performance of sales by quarter, by year, and by geographic regions, in order to fine-tune production strategies.(3) analyzing operations and looking for sources of profit.(4) managing the customer relationships, making environmental corrections, and managing the cost of corporate assets.Data warehousing is also very useful from the point of view of heterogeneous database integration. Many organizations typically collect diverse kinds of data and maintain large databases from multiple, heterogeneous, autonomous, and distributed information sources. To integrate such data, and provide easy and efficient access to it is highly desirable, yet challenging. Much effort has been spent in the database industry and research community towards achieving this goal.The traditional database approach to heterogeneous database integration is to build wrappers and integrators (or mediators) on top of multiple, heterogeneous databases. A variety of data joiner and data blade products belong to this category. When a query is posed to a client site, a metadata dictionary is used to translate the query into queries appropriate for the individual heterogeneous sites involved. These queries are then mapped and sent to local query processors. The results returned from the different sites are integrated into a global answer set. This query-driven approach requires complex information filtering and integration processes, and competes for resources with processing at local sources. It is inefficient and potentially expensive for frequent queries, especially for queries requiring aggregations.Data warehousing provides an interesting alternative to the traditional approach of heterogeneous database integration described above. Rather than using a query-driven approach, data warehousing employs an update-driven approach in which information from multiple, heterogeneous sources is integrated in advance and stored in a warehouse for direct querying and analysis. Unlike on-line transaction processing databases, data warehouses do not contain the most current information. However, a data warehouse brings high performance to the integrated heterogeneous database system since data are copied, preprocessed, integrated, annotated, summarized, and restructured into one semantic data store. Furthermore, query processing in data warehouses does not interfere with the processing at local sources. Moreover, data warehouses can store and integrate historical information and support complex multidimensional queries. As a result, data warehousing has become very popular in industry.1.Differences between operational database systems and data warehousesSince most people are familiar with commercial relational database systems, it is easy to understand what a data warehouse is by comparing these two kinds of systems.The major task of on-line operational database systems is to perform on-line transaction and query processing. These systems are called on-line transaction processing (OLTP) systems. They cover most of the day-to-day operations of an organization, such as, purchasing, inventory, manufacturing, banking, payroll, registration, and accounting. Data warehouse systems, on the other hand, serve users or “knowledge workers" in the role of data analysis and decision making. Such systems can organize and present data in various formats in order to accommodate the diverse needs of the different users. These systems are known as on-line analytical processing (OLAP) systems.The major distinguishing features between OLTP and OLAP are summarized as follows.(1)Users and system orientation: An OLTP system is customer-oriented and is used for transaction and query processing by clerks, clients, and information technology professionals. An OLAP system is market-oriented and is used for data analysis by knowledge workers, including managers, executives, and analysts.(2)Data contents: An OLTP system manages current data that, typically, are too detailed to be easily used for decision making. An OLAP system manages large amounts of historical data, provides facilities for summarization and aggregation, and stores and manages information at different levels of granularity. These features make the data easier for use in informed decision making.(3)Database design: An OLTP system usually adopts an entity-relationship (ER) data model and an application -oriented database design. An OLAP system typically adopts either a star or snowflake model, and a subject-oriented database design.(4)View: An OLTP system focuses mainly on the current data within an enterprise or department, without referring to historical data or data in different organizations. In contrast, an OLAP system often spans multiple versions of a database schema, due to the evolutionary process of an organization. OLAP systems also deal with information that originates from different organizations, integrating information from many data stores. Because of their huge volume, OLAP data are stored on multiple storage media.(5). Access patterns: The access patterns of an OLTP system consist mainly of short, atomic transactions. Such a system requires concurrency control and recovery mechanisms. However, accesses to OLAP systems are mostly read-only operations (since most data warehouses store historical rather than up-to-date information), although many could be complex queries.Other features which distinguish between OLTP and OLAP systems include database size, frequency of operations, and performance metrics and so on.2.But, why have a separate data warehouse?“Since operational databases store huge amounts of data", you observe, “why not perform on-line analytical processing directly on such databases instead of spending additional time and resources to construct a separate data warehouse?"A major reason for such a separation is to help promote the high performance of both systems. An operational database is designed and tuned from known tasks and workloads, such as indexing and hashing using primary keys, searching for particular records, and optimizing “canned" queries. On the other hand, data warehouse queries are often complex. They involve the computation of large groups of data at summarized levels, and may require the use of special data organization, access, and implementation methods based on multidimensional views. Processing OLAP queries in operational databases would substantially degrade the performance of operational tasks.Moreover, an operational database supports the concurrent processing of several transactions. Concurrency control and recovery mechanisms, such as locking and logging, are required to ensure the consistency and robustness of transactions. An OLAP query often needs read-only access of data records for summarization and aggregation. Concurrency control and recovery mechanisms, if applied for such OLAP operations, may jeopardize the execution of concurrent transactions and thus substantially reduce the throughput of an OLTP system.Finally, the separation of operational databases from data warehouses is based on the different structures, contents, and uses of the data in these two systems. Decision support requires historical data, whereas operational databases do not typically maintain historical data. In this context, the data in operational databases, though abundant, is usually far from complete for decision making. Decision support requires consolidation (such as aggregation and summarization) of data from heterogeneous sources, resulting in high quality, cleansed and integrated data. In contrast, operational databases contain only detailed raw data, such as transactions, which need to be consolidated before analysis. Since the two systems provide quite different functionalities and require different kinds of data, it is necessary to maintain separate databases.数据仓库数据仓库为商务运作提供了组织结构和工具，以便系统地组织、理解和使用数据进行决策。
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
计算机专业毕业设计外文翻译
近几年来，随着计算机的普及和建筑电子产业的发展，人们对居住环境要求的不断提高，智能化的住宅不仅成为房地产开发商投资的重点，而且也是人们购房的新热点。
智能小区是指可以为社区居民提供计算机网络、智能家居、物业服务和管理、电子商务平台、社区服务信息网等全方位信息服务的多媒体综合信息系统。
通过这些服务，用户可以实现高速INTERNET接入、网上教育、网上游戏、家中视频点播等多种功能，还可实现办公家居自动化管理。
因此对于小区的中心机房，在考虑其中心机房的装修，配电系统，空调系统，防雷系统，消防安全系统等方面的同时，网络服务系统是中心机房的核心部分。
所以，在本论文中是围绕了小区网络中心机房的网络和设备设计与实现。
论文的重点是网络方案的选定，网络拓扑的设计及综合布线的设计和服务器。
并从其规划、设计、实施等方面介绍局域网、常见的接入网技术的比较、网络设备的选择和管理，以及对网络有直接影响的布线等方面做一个全面的分析和比较，从而确定论文所要解决的所有关的课题。
其次还有对机房部分的安全，消防等工作的确定。
关键词：智能小区；中心机房；网络拓扑；综合布线；网络设备
In recent years, with the popularization of computer, the development of the construction of electronic industry, and the continuous improvement of the requirements of the living environment ,intelligent residential become not only the focus of investment for real estate developers, but also new hot spot of pruchase. Intelligent community is that for community residents to provide computer network, intelligent home furnishing, property services and management, e-commerce platform, community service information network, a full range of information services of multimedia integrated information system. Through this service, users
The paper focuses on the selection of the network scheme, the design of network topology ,the design of integrated wiring and the server. And from the planning, design, implementation, the paper introduces the local area network, comparison of common access network technology, selection and management of network equipment, as well as a comprehensive analysis and comparison of the wiring and other aspects that have a direct effect on the network, thereby determining the thesis to solve all the problem. Secondly there is also determination of safety, fire protection and other work.
Keywords: intelligent community; central computer room; network topology; integrated wiring; network equipment。