Mac OS/OS X

Mac OS X The Operating System created by combining Darwin?, an Open Source kernel based on the BSD source tree and the Mach microkernel, with a custom Apple GUI. The Darwin kernel provides an extremely stable and flexible operating system which rivals many Unix implementations. OS X's users consider its GUI to be the most beautiful and functional in existence. It is a powerful combination, but analysts are still waiting to see the long term effects on the computer industry.

OS X is compatible with the previous versions of the Mac OS by using the Classic application, which runs Mac OS 9.x under emulation (the application runs in the background; any applications appear to run like OS X applications.

OS X can run many BSD or Linux software packages, when they've been compiled for the platform. Compiled binaries are normally distributed as OS X Packages; but may still require command-line configuration or compilation. Companies such as Fink provide precompiled or preformatted packages for many standard packages.