【正文】 另外，在系統(tǒng)開發(fā)過程中 ＊＊ 同學 也給于我很大的幫助，幫助解決了不少的難點，使得系統(tǒng)能及時開發(fā)完成，還有同 班 的同學同樣給與我不少幫助，這里表示感謝 ! 第十一部分：主要參考文獻 書名 作者 出版社 1. 《 Visual C ++ 實例教程》 門檻創(chuàng)作室 電子工業(yè)出版社 2. 《 Visual C ++ 自學捷徑》 韋源 北京大學出版社 3. 《 SQL Server 2020 入門與提高》周緒、管麗娜 清華大學出版社 第九部分結論 34 4. 《 Visual C ++ 學習教程》 凌賢伍、吳永禮 北京大學出版社 5. 《 C++ 語言程序設計》 鄭莉、董淵 清華大學出版社 6. 《 Visual C++ 實例導航》 李閩溟、吳繼剛 人民郵電出版社 7. 《 Visual C++ 24 學時學習教程》 Mickey Williams 機械工業(yè)出版社 8. 《軟件工程導論》 張海藩 清華大學出版社 9. 《 Visual C++ 入門與提高》徐曉剛、王秀娟 清華大學出版社 第九部分結論 35 附錄 1 英文及其譯文 Computer Networks Network Goals Some reasons are causing centralized puter systems to give way to works. The first one is that many anizations already have a substantial number of puters in operation, often located far apart .Initially, each of these puters may have worked in isolation from the other ones, but at a certain time, and management may have decided to connect them to be able to correlate information about the entire anization. Generally speaking, the goal is to make all programs, data, and other resources available to anyone on the work without regard to the physical location of the resource and the user. The second one is to provider high reliability by having alternative sources of supply. With a work, the temporary loss of a single puter is much less serious, because its users can often be acmodated elsewhere until the service is restored. Another important reason for distributing puting power has to do with the relative price of puting versus munication. Now the cost of a small puter is negligible, so it bees attractive to analyze the data at where it is captured, and only to send occasional summaries back to the puter center, to reduce the munication cost, which now represents a larger percentage of the total cost than it used to. Yet another reason of setting up a puter work is that a puter work can provider a powerful munication medium among widely separated people. Application of Networks One of the main areas of potential work use is access to remote 第九部分結論 36 data bases. It may someday be easy for people sitting at their terminals at home to make reservations for airplanes, trains, bused, boats, restaurants, theaters, hotels, and so on, at anywhere in the world with instant confirmation. Home banking, automated newspaper and fully automated library also fall in this category. Computer aided education is another possible field for using work, with many different coursed being offered. Teleconferencing is a whole new form of munication. With it, widely separated people can conduct a meeting by typing messages at their terminals. Attendees may leave at will, and find out what they missed when they e back. International contacts by human being may be greatly enhanced by work based munication facilities. Network Structure In any work exists a collection of machines intended to running user (., application) program. These machines are called hosts. The hosts are connected by the munication sub. The job of the sub is to carry messages from host to host. The sub consists of two basic ponents: nodes and channels. Nodes are specialized puters. All traffic to or from the host goes via its node. Channels are transmission lines. Broadly speaking, there are two general types of designs for the munication sub: (1)Pointtopoint channels (2Broadcast channels In the first one, the work contains numerous cables or leased telephone lines, each one connecting a pair of nodes. If two nodes that do not share a cable wish to municate, they must do this indirectly via other nodes. When a message is sent from one node to another via one or more inter mediate nodes, each intermediate node will receive the 第九部分結論 37 message and store it until the required output line is free so that it can transmit the message forward. The sub using this principle is called a pointtopoint or storeandforward sub. When a pointtopoint subset is used, the important problem is how to design the interconnected topology between the nodes. The second kind of munication architecture uses broadcasting. In this design there is a single munication channel shared by all nodes. The inherence in broadcast system is that messages sent by any node are received by all other nodes. Protocol Hierarchies To reduce their design plexity, most works are anized as a series of layers or levels, each one built upon its predecessor. Layer n on one machine carries on a conversation with layer n on another machine. The rules and conventions used in this conversation are collectively called the layer n protocol. In reality, no data are directly transferred from layer n on one machine to layer n on another machine (except in the lowest layer).Instead, each layer passes data and control information to the following layer immediately, until the lowest layer is reached. At the lowest layer there is one physical munication with the other machine, as opposed to the virtual munication used by the higher layers. Between each pair of adjacent layers there is an interface. The interface defines which primitive operations and services the lower offers to the upper one. The set of layers and protocols is called work architecture. Design Issues for the Layers One set of design decisions are the rules for data transfer. Do data only travel in one direction, called simplex munication, or travel in either direction, but not simultaneously, called halfduplex 第九部分結論 38 munication, or travel in both directions at once, call fullduplex municative? Error control is an impo