The BeOS is, quite simply, an operating system. An operating system provides programmers with a means of performing input and output to and from the hardware of a computer. For instance, an operating system helps applications display information on the screen, and tells applications where the user clicked the mouse. Computers can often run several different operating systems; Intel-based PCs can run Windows 3.1, Windows 95, or Windows NT, for instance, while Power Macintosh hardware could only run the Mac OS. Now users of either hardware platform have an additional choice: the BeOS.