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). Or

A machine that stores programs and information in electronic form and can be used for a variety of processes, for example writing, calculating, and communicating on the Internet (www.macmillandictionary.com). Or

A computer is a device that accepts information (in the form of  Digitalized  data) and manipulates it for some result based on a program or sequence of instructions on how the data is to be processed. Complex computers also include the means for storing data (including the program, which is also a form of data) for some necessary duration.

A program may be invariable and built into the computer (and called logic circuitry as it is on microprocessors) or different programs may be provided to the computer (loaded into its storage and then started by an administrator or user). Today's computers have both kinds of programming.