2. Purpose of a file

In order for a computer to do any work, it has to have data flowing through the CPU (central processing unit) under the control of a program.

That data has to come from somewhere, and much of the time it comes from a stored file.

A program loads the file from storage into main memory and then feeds it through the CPU to produce an output.

That output could be a number of things :

• Another data file
• Screen images (graphs, text and so on)
• Moving images (video, animation)
• Sound (music, voice or other sounds)

Of course the output is often a combination of these types. For example, playing back a movie file will have video and sound being produced at the same time.

A word processor will have text and images being produced on the screen and usually a saved file every few minutes.