Mainframe Computers

A very large and expensive computer capable of supporting hundreds, or even
thousands, of users simultaneously. In the hierarchy that starts with a simple
microprocessor (in watches, for example) at the bottom and moves to supercomputers at
the top, mainframes are just below supercomputers. In some ways, mainframes are more
powerful than supercomputers because they support more simultaneous programs. But
supercomputers can execute a single program faster than a mainframe. The distinction
between small mainframes and minicomputers is vague (not clearly expressed),
depending really on how the manufacturer wants to market its machines.