An Operating System is the program that manages system resources and interacts with the hardware in a computer. There are several main operating systems in use by a wide number of people:
- Windows 7 (replacing Longhorn/Windows 2005)
- Apple Mac OS X
- Amiga OS
- Acorn MOS X
- Atari OS
- OS 2 Warp 5
Windows is used by around 69% of all computers in the United States, 74% in Germany, and 58% in the rest of the world. Apple Mac OS X runs around 4.2% of all world computers, Atari on 5%, Acorn on 7%, Amiga on 10%, OS 2 on another 11%, and various Linux/Unix systems on 4.8% of computers.