Definition of mainframe in The Network Encyclopedia.

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What is Mainframe?

A general term for a high-level, typically large computer that is capable of performing demanding computational tasks. Vendors of mainframes include IBM, Unisys, and Hitachi Data Systems.

Mainframe computers were historically operated as centralized computing systems to which dumb terminals were attached through local network connections and remote dial-up connections. Users entered text-based commands into these terminals, and the terminal forwarded the commands to the mainframe, where all the processing was performed.

The results of the processing were returned to the terminal and displayed. Modern mainframes offer terminal communication but also support connections to “smart terminals” - desktop computers that are connected to the mainframe but also have their own computing power.

Much of the computing performed in the government, financial, and industrial sectors still uses mainframes for such functions as database processing, transactions, accounting, and payroll. To access data stored on a mainframe, distributed-computing systems such as Microsoft Windows 2000 can use a Microsoft BackOffice product called Microsoft SNA Server. Internet Information Services (IIS) can also use components of SNA Server and Active Server Pages (ASP) technology to build distributed Web-based applications that provide browser-based access to mainframe data.

IBM’s line of mainframes has evolved to the point that its System/390 mainframe platform can be used for distributed client/server computing and Web-based computing. A modern mainframe can thus be considered a very big server that can easily be integrated with Windows 2000 or other servers into local area networks (LANs) or wide area networks (WANs).

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