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, depending really on how the manufacturer wants to market its machines.