A term originally referring to the cabinet containing the central processor unit or "main frame" of a room-filling stone age batch machine. After the emergence of smaller "minicomputer" designs in the early 1970s, the traditional big iron machines were described as "mainframe computers" and eventually just as mainframes. The term carries the connotation of a machine designed for batch rather than interactive use, though possibly with an interactive time-sharing operating system retrofitted onto it; it is especially used of machines built by ibm, unisys and the other great dinosaurs surviving from computing's stone age.

It has been common wisdom among hackers since the late 1980s that the mainframe architectural tradition is essentially dead (outside of the tiny market for number crunching supercomputers (see cray)), having been swamped by the recent huge advances in integrated circuit technology and low-cost personal computing. As of 1993, corporate America is just beginning to figure this out - the wave of failures, takeovers, and mergers among traditional mainframe makers have certainly provided sufficient omens (see dinosaurs mating).

Supporters claim that mainframes still house 90% of the data major businesses rely on for mission-critical applications, attributing this to their superior performance, reliability, scalability, and security compared to microprocessors.

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