A computer is a machine that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming.
Modern computers have the ability to follow generalized sets of operations, called programs. These programs enable computers to perform an extremely wide range of tasks. (Source: Wikipedia)
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:
- Central processing unit (CPU): The heart of the computer, this is the component that actually executes instructions organized in programs (“software”) which tell the computer what to do.
- Memory (fast, expensive, short-term memory): Enables a computer to store, at least temporarily, data, programs, and intermediate results.
- Mass storage device (slower, cheaper, long-term memory): Allows a computer to permanently retain large amounts of data and programs between jobs. Common mass storage devices include disk drives and tape drives.
- Input device: Usually a keyboard and mouse, the input device is the conduit through which data and instructions enter a computer.
- Output device: A display screen, printer, or other device that lets you see what the computer has accomplished.