A modern electronic computer is a machine that is meant for Input, storage,manipulation and outputting of data.
A computer is a machine that can be programmed to accept data (input), process it into useful information (output), and store it away (in a secondary storage device) for safekeeping or later reuse. The processing of input to output is directed by the software but performed by the hardware.
A computer is a device 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.
An input device is a piece of hardware that is used to enter data into a computer or a similar processing device such as a smart phone. Input devices are usually categoried as either manual or automatic. Examples of manual input devices are: Keyboard. Mouse.