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The era of instant access to information has arrived. In the past, it was difficult to retrieve and manipulate data because much corporate information was stored in files kept on mainframe computers that were accessible only to information systems (IS) professionals. The development of personal computers changed all that. Users expect to be able to get the information they want, in the form they want it, when they want it.
When information was costly to collect and manipulate, "the constraining variable was the availability of data, not the need for it."(1) When data were scarce, accountants agreed on fixed reporting formats. Now management wants accountants to manipulate data in ways that are appropriate for today's problems, without regard for familiar fixed formats.(2) Client/server, a cooperative form of computing, lets this happen from the user's desktop.
WHAT IS CLIENT/SERVER COMPUTING?
Client/server computing, as its name implies, processes information via two or more computers connected in such a way that users perceive the system as an integrated whole. The user's workstation or PC works with data maintained on another computer. The workstation is called the client, and the computer on which the data are maintained is called the server. The server may be another PC, a workstation, a minicomputer, a mainframe, or a combination of several computers, and it can provide data to many clients.
Before client/server computing, when application systems were kept only on centralized mainframe computers, terminals displayed data and reports in fixed formats. When medium-sized computers were used as the host processor, this configuration became known as host-based processing. (See Figure 1, leftmost part.) (Figure 1 omitted) The computer actually running the application is known as the host, and the only function for the user's terminal is to request and display predefined input and output screens.
By the mid-1980s, many terminals were replaced by PCs that could emulate terminals. Emulating a terminal means that the PC is running a program, such as ProComm or CrossTalk, that allows it to respond as if it were a terminal connected to the host computer. The advantage of terminal emulation is that users have a device that does more than just perform as a dedicated terminal.
Client/server applies when the user's PC -- the client -- participates in...