What is a 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).
Modern Computers Defined :-
Modern computers are electronic and digital. The actual machinery wires, transistors, and circuits is called hardware; the instructions and data are called software.
All general-purpose computers require the following hardware components:
Memory enables a computer to store, at least temporarily, data and programs.
Mass storage device :-
Mass storage device allows a computer to permanently retain large amounts of data. Common mass storage devices include disk drives and tape drives.
Input device :-
Input device usually a keyboard and mouse, the input device is the conduit through which data and instructions enter a computer.
Output device :-
Output device a display screen, printer, or other device that lets you see what the computer has accomplished.
Central processing unit (CPU) :-
CPU is the heart of the computer, this is the component that actually executes instructions.
In addition to these components, many others make it possible for the basic components to work together efficiently. For example, every computer requires a bus that transmits data from one part of the computer to another.
Computer Classification, By Size and Power :-
Computers can be generally classified by size and power as follows, though there is considerable overlap:
Personal computer :-
Personal computer is a small, single-user computer based on a microprocessor. In addition to the microprocessor, a personal computer has a keyboard for entering data, a monitor for displaying information, and a storage device for saving data.
Workstation is a powerful, single-user computer. A workstation is like a personal computer, but it has a more powerful microprocessor and a higher-quality monitor.
Minicomputer is a multi-user computer capable of supporting from 10 to hundreds of users simultaneously.
Mainframe is a powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously.
Supercomputer is an extremely fast computer that can perform hundreds of millions of instructions per second.