【導(dǎo)讀】本文介紹了賓館客房管理信息系統(tǒng)的開(kāi)發(fā)過(guò)程。論文詳盡論述了從需求分析、系統(tǒng)分。本系統(tǒng)今后的改進(jìn)方向。遵循軟件工程的方法。追加押金、調(diào)房登記、退房結(jié)賬、客房設(shè)置、客房客房設(shè)置、客房查詢、開(kāi)發(fā)工具，采用成熟的軟件研制技術(shù)，后臺(tái)數(shù)據(jù)庫(kù)采用SQL2020。-------使用面向?qū)ο蟮脑O(shè)計(jì)實(shí)現(xiàn)的原因。所以，實(shí)現(xiàn)本系統(tǒng)VC是一個(gè)相對(duì)較好的選擇。．幫助文件的制作。

　　

【正文】 aving 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(jié)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(jié)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(jié)論 38 munication, or travel in both directions at once, call fullduplex municative? Error control is an important issue when the physical munication circuits are not perfect. Many errordetecting and errorcorrecting codes are known, but both ends of the connection must agree on what kind of code is being used. In addition, the receiver must have some way of telling the sender which messages have been correctly received and which has not. When there are multiple paths between source and destination, at some points in the hierarchy, a routing decision must be made. The ISO Reference Model The Reference Model of Open System Interconnection (OSI), as ISO calls it, has seven layers. The major ones of the principles, from which ISO applied to get the seven layers, are as follows: (1) A layer should be created where a different level of abstractions is needed. (2) Each layer should perform a well defined function. (3) The function of each layer should be chosen with an eye toward defining internationally standardized protocols. (4) The layer boundaries should be chosen to minimize the information flow across the interfaces. (5) The number of layers should be large enough so that distinct functions need not be put together in the same layer without necessity, and small enough so that the architecture will not bee out of control. The Physical Layer The physical layer is concerned with transmitting raw bits over a munication channel. Typical questions here are