technoguy

Mainframes (often colloquially referred to as big iron) are computers used mainly by government institutions and large companies for mission critical applications, typically bulk data processing such as census, industry/consumer statistics, ERP, and financial transaction processing.

vipl

Mainframe computers are large, expensive, ultra-fast computers. Used generally of number-crunching supercomputers, but can include more conventional big commercial IBMish mainframes. Modern mainframe computers have abilities not so much defined by their performance capabilities as by their high-quality internal engineering. The growth of e-business has also dramatically increased the number of backend transactions processed by tried-and-true mainframe software as well as the size and throughput of databases. Mainframe acquisition prices vary is somewhat misleading, however, because IBM mainframe processors are "owned forever" — customers only pay a frame charge for a model upgrade and do not have to repurchase processor capacity. Prices also generally include generous maintenance and service terms that are quite unlike other computers.