4.1, network structure mode

1. C/S structure

① Introduction to C/S structure

• server-client, Client - Server（C/S）the structure . C/SThe structure usually adopts a two-layer structure. The server is responsible for data management, and the client is responsible for completing the interactive tasks with users. A client computer is a machine on the Internet that accesses other people's information, and a server is a computer that provides information for human access.
• The client is connected to the server through the local area network , accepts the user's request, and makes a request to the server through the network to operate the database. The server accepts the client's request, submits the data to the client, and the client calculates the data and presents the result to the user. The server also needs to provide comprehensive security protection and data integrity processing, and allows multiple clients to access the server at the same time, which puts forward high requirements on the server's hardware processing data capabilities.
• In C/Sthe structure, the application is divided into two parts: the server part and the client part. The server part is the information and functions shared by multiple users, and performs background services, such as controlling the operation of the shared database ; function, and can freely switch between subroutines.

② Advantages of C/S structure

1. It can give full play to the processing ability PCof , and many tasks can be submitted to the server after the client processes, so C/Sthe response speed of the structural client is fast;
2. The operation interface is beautiful and diverse, which can fully meet the individual requirements of customers;
3. C/SThe structured management information system has strong transaction processing capabilities and can realize complex business processes;
4. High security, C/Sgenerally oriented to a relatively fixed user group, the program pays more attention to the process, it can perform multi-level verification of permissions, provides a more secure access mode, and has a strong ability to control information security, generally highly confidential It is appropriate for the information system to adopt the C/S structure.

③ Disadvantages of C/S structure

1. The client needs to install special client software. First of all, it involves the workload of installation, and secondly, any problem with a computer, such as virus or hardware damage, needs to be installed or maintained. When the system software is upgraded, each client needs to be reinstalled, and the maintenance and upgrade costs are very high;
2. There are generally restrictions on the operating system of the client, and it cannot be cross-platform.

2. B/S structure

① Introduction to B/S structure

• The B/S structure (Browser/Server, browser/server mode) is a network structure mode after the rise of the WEB, and the WEB browser is the most important application software for the client. This mode unifies the client, concentrates the core part of system function realization on the server, and simplifies the development, maintenance and use of the system. As long as a browser is installed on the client computer, such as Firefoxor Internet Explorer, the server installs SQL Server, Oracle, MySQLand other databases. The browser interacts with the Web Serverdatabase data.

② Advantages of B/S structure

• B/SThe biggest advantages of the architecture are low overall cost of ownership, convenient maintenance, strong distribution, and simple development. It can be operated anywhere without installing any special software. The client has zero maintenance and the system is very easy to expand. As long as there is one Computers with Internet access can be used.

③ Disadvantages of B/S structure

1. The communication overhead is large, and the security of the system and data is difficult to guarantee;
2. The individual characteristics are obviously reduced, and the functional requirements with individuality cannot be realized;
3. The protocol is generally fixed:http/https
4. The interaction between the client and the server is a request-response mode . Usually, the page is dynamically refreshed, and the response speed is significantly reduced.