The Mainframe Computer

The mainframe is the largest general-purpose computer. It was also the first computer to be used in business, dating back to the early 1950s. It is designed to be used by hundreds — even thousands — of people. Mainframes generally cost at least $700,000 and must be housed in special rooms where temperature and humidity are carefully maintained within certain limits. Most mainframes are employed in situations with continual, heavy processing and many users.

Mainframes consist of the basic building blocks of a computer system: the CPU, various I/O devices, and external memory. The main difference is that these building blocks are considerably larger than, say, a personal computer's. In some cases, mainframes are so large that there is more than one CPU. There might be a cluster of CPU cabinets forming a very powerful mainframe that requires so much main memory that it, too, takes several cabinets to house. In almost all mainframe systems, the controller is in a separate cabinet as well.

An extensive array of peripheral equipment is connected to the mainframe: terminals, a variety of printers, many different kinds of storage devices, and communications equipment. A mainframe uses the same peripherals you will find with a minicomputer or a personal computer. What sets the mainframe apart from other types of computers is its powerful CPU, its vast memory and storage capabilities, and the number of terminals that can be connected. For example, Pillsbury, the food products company with headquarters in Minneapolis, has built an entire underground building the size of a football field to house its mainframe computer equipment.