CLIENT-SERVER COMPUTING (STUDY OBJECTIVE 3)

Since the mid-to-late 1980s, the client–server model of networks has been commonly used. Client–server computing means that there are two types of computers networked together to accomplish the application processing. The server is usually a large computer that contains the database and many of the application programs. Client computers, usually PC-type computers, are networked to the server and work with the server in such a way that the network appears to be one integrated system for users. The advantage of client-server computing is that the PC clients perform as “smart” terminals that can accomplish some share of the processing tasks. In most client-server networks, the server manages and stores the large database, extracts data from the database, and runs the large, complex application programs. The client PC usually works with a subset of data that has been extracted from the server database to accomplish some local processing tasks.

For an example of client–server computing, let us assume that a large national corporation has several regional managers. Each regional manager oversees sales and collection of receivables for his or her area. A manager in Milwaukee, Wisconsin may have a feeling that there is an extremely high number of uncollectible accounts in certain parts of Milwaukee and would like to examine a report to confirm or allay this suspicion. The large database of customers and their receivables balances would reside on the server. The regional manager in Milwaukee would use her client PC to write a query to extract the overdue customer accounts in Milwaukee from the server. This query travels through the network to the main server, which extracts the customer records requested. This subset of customer records is sent to the client PC, where the regional manager can use software to map locations of overdue accounts. Such a map would help the manager review and manage the uncollectible accounts. This scenario is an example of client-server computing, and it exhibits the main characteristics of client server systems. Those characteristics are as follows:

1. Client and server computer are networked together.
2. The system appears to users to be one integrated whole.
3. Individual parts of processing are shared between the server and client.
4. The client computer participates in the processing or data manipulation in some meaningful way.

In client–server computing, the tasks are assigned to either the server or the client on the basis of which one can handle each task most efficiently. The server is more efficient in managing large databases, extracting data from databases, and running high-volume transaction processing software applications. The client is more efficient manipulating subsets of data and presenting data to users in a user-friendly, graphical-interface environment.

Client–server computing can be divided into two levels: distributed presentation and distributed applications.

A large number of client-server applications are now moving toward a Web-based model. This model of IT is described in the next section.