Operating systems usually come preloaded on any computer that you buy. Most people use the operating system that comes with their computer, but it is possible to upgrade or even change operating systems.
The Windows, OS X, and Linux logosModern operating systems use a Graphical User Interface, or GUI (pronounced "gooey"). A GUI lets you use your mouse to click on icons, buttons, and menus, and everything is clearly displayed on the screen using a combination of graphics and text.
The three most common operating systems for personal computers are Microsoft Windows, Apple Mac OS X, and Linux.
The Windows, OS X, and Linux logos