Prior to the advent of the personal computer or PC, the minicomputer, and the microcomputer, the term "computer" simply referred to mainframes. What differentiates the modern mainframe from these other classes of computers is the scope of the processing taking place. The typical mainframe today serves tens of thousands of users processing thousands of transactions every second while maintaining centralized terabyte -size databases. Even the mighty supercomputer, although unquestionably faster doing one thing at a time, is not up to this task.

Surprisingly, the processors used in these machines are not much faster than those found in PCs. The architecture of the mainframe, however, provides that the processors can work together in parallel and focus primarily on the actual processing of data and instructions. They are relieved of the time-consuming duties of controlling input and output. Mundane tasks such as reading data from disk, handling transmissions to user...