Computer   A computer is a programmable machine. The two principal characteristics of a computer are: It responds to a specific set of instructions   in a well-defined manner and it can   execute   a prerecorded list of instructions (a   program ).

Super computer
Mainframe
Computer
Micro
Computer
T he fastest type of   computer . Supercomputers are very expensive and are employed for specialized   applications   that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated   graphics , fluid dynamic calculations, nuclear energy research, and petroleum exploratio n.
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 .
The term microcomputer   is generally synonymous with  personal computer , or a computer that depends on a   Microcomputers are designed to be used by individuals, whether in the form of PCs,  work station   or  note books.