An operating system is the essential software that's needed to run your computer's suite of software. Everything from video games to web browsing, basic word processing, and more is down thanks to ...

The computer's master control program. When a computer is turned on, a small "boot program" loads the operating system. Although additional system modules may be loaded as needed, the main part ...

A well thought out GUI is crucial for modern operating systems, as that interface will govern the vast majority of tasks performed on that computer. Common examples include Windows and Mac OS X.

What does operating system software actually mean? Find out inside PCMag's comprehensive tech and computer-related encyclopedia.