According to the SearchWin 2000 database, an operating system (sometimes abbreviated as "OS") is the program that, after being initially loaded into the computer by a boot program, manages all the other programs in a computer.

The other programs are called applications or application programs. The application programs make use of the operating system by making requests for services. In addition, users can interact directly with the operating system through a user interface such as a command language like DOS.

They can also interact with the operating system via a graphical user interface (GUI, pronounced 'gooey'). Think of the GUI as the graphical representation of the Operating System. It's all the buttons and pictures and icons and menus that you see on your screen.

So for instance, when you move your cursor around the desktop on a Mac or PC you are interacting with the GUI and thus, the operating system.

Both the hardware and the software on a computer require the operating system to make them perform together and provide you with a satisfying computing experience (at least most of the time). Windows, Mac OS, Unix and Linux are all examples of operating systems.

In today's world, the most common home and office operating systems are the Mac OS and Windows. Now there are several versions of the Windows Operating System including Windows 2000, NT, 98, ME, and now XP. The Mac OS has progressed linearly and their newest OS at this point is OS 10.