The term computer refers to an electronic device that can be programmed to perform calculations. Calculators, alarm watches, and CD players all have them. But when we hear "computer" we tend to think of a desktop computer.
 
A computer has 3 primary functions. The first function is to receive input from the user. This can be done in many formats, from typing a command on the keyboard, to clicking the mouse. After the computer has handled the user's input, it performs the second function, called processing. In this step, the computer interprets the user's input and decides what to do with it. After processing the input, the computer must display its work, called output. This can be done through a monitor, a printer, speakers, etc. A secondary function of a computer is storage. Storage involves retaining data for later use. This stored data can then be exchanged by the processing function. The flow chart below explains this process:

As you can see, the flow chart demonstrates that the input from the user is directed to the processing function. The processing function interprets the input and turns it into output. A secondary storage function also exchanges data with the processing function. Every component of a computer pertains to one of these functions.