The operating system defines our computing experience. It's the first software we see when we turn on the computer, and the last software we see when the computer is turned off. It's the software that enables all the programs we use. The operating system organizes and controls the hardware on our desks and in our hands, yet most users can't say with any certainty precisely what it is that the operating system does.

In this edition of HowStuffWorks, we'll tell you what a piece of software must do to be called an operating system, and show you how the operating system works to turn a collection of hardware into a powerful computing tool!