2015-09-06
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Associated with increased decentralization environment was developed architecture "client-server". By using this architecture as centralized information processing also requires a central computer - the server. But its functions other than the mainframe. Client computers query the server for the required data, processes it, and send back. Applications written for the architecture "client -server", usually consist of a separate server and client components. Server (server) called a computer that provides access to its resources to other computers called clients. Client can be one of two types: a thick client or thin client.
In general, the client and server can reside on the same computer. Using a database management system, built on the architecture of the "client - server" provides the following benefits:
1. Centralized data storage; 2. Reduction of network traffic;
3. Better administrative databases.
Three-tier architecture "client / server" has many advantages over the one-and two-level models, some of them: - For the "thin" client requires less expensive hardware. - Centralize business logic for many end-users on a single server application and, as a consequence, the centralization of support applications. This eliminates the need to deploy the software on multiple computers, which is one of the most difficult tasks in the two-level model "client / server ". - More modularity simplifies the modification or replacement of software each level without affecting other layers. - Branch of the main business logic from database functions simplifies the task of load balancing.
An additional advantage is that the three-tier architecture is quite natural environment displayed on WWW, where the browser plays the role of "thin" client and the web server - application server. Three-tier architecture can be extended to N- tier architecture with additional levels that will improve the flexibility and scalability to create applications. For example, an intermediate level in the three-tier architecture can be split into two levels, one of which can perform tasks a normal web server, and the other - a typical application server.
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56.Browsers and servers.
Most of us surf the Internet several times a week, if not several times a day. We visit website after website, viewing information, playing games, and occasionally downloading software. The World Wide Web is an incredible spectacle, but none of it would exist without web servers. Web servers are the backbone of the web, since they are responsible for serving up every web page you see. Most people take the Internet for granted. It takes a lot of work to do something as simple as display a web page. When you clicked on the link to view this article, a series of smaller operations commenced which, while each is small on their own, all fit together to bring you this brilliantly written composition. A webbrowser (commonly referred to as a browser) is a software application for retrieving, presenting and traversing information resources on theWorld Wide Web. An information resource is identified by a Uniform Resource Identifier (URI/URL) and may be a web page, image, video or other piece of content. Hyperlinks present in resources enable users easily to navigate their browsers to related resources.
Although browsers are primarily intended to use the World Wide Web, they can also be used to access information provided by web servers in private networks or files in file systems.
The major web browsers are Google Chrome, Mozilla Firefox, Internet Explorer, Opera, and Safari.
