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n. This term originally referred 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 timesharing 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 is common wisdom among hackers 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 IC technology and low-cost personal computing. As of 1991, corporate America hasn't quite figured this out yet, though the wave of failures, takeovers, and mergers among traditional mainframe makers are certainly straws in the wind (see dinosaurs mating).