The OS created by Apple and originally used by Macs is frequently (albeit slightly incorrectly) referred to as Mac OS Classic (officially Mac OS Classic is this original OS running under the modern Mac OS X in emulation. Mac OS combines the functionality of both an OS and a window manager and is often considered to be the easiest OS to use. It is partially multitasking but will still sometimes crash when dealing with a buggy program. It is probably the second most popular OS, next only to Windows 'XP (although it is quickly losing ground to Mac OS X) and has excellent driver support and boasts a fair selection of games. Mac OS will run on PowerPC and 68xx based machines.