Darwin is the basic "core" of OS X , the operating system for Apple's Macintosh , and combines two well-known programs, the Mach kernel and FreeBSD, in a strategic move by Apple to make its future operating systems based on and available to others as open source code. Traditionally, major computer makers have treated their operating systems (and most applications) as proprietary. Making the source code available freely to outside developers is designed to encourage any developer to create improvements or fix problems. In addition to Darwin, OS X includes its own proprietary user interfaces and other special features that are not offered as open source.
Historically, a Macintosh operating system has required a special investment in learning for application developers. For OS X, Apple chose to build a new operating system based on a variation of the open UNIX operating system, a system that is very stable and also familiar to a large body of developers. Apple chose the FreeBSD variation of BSD, itself a packaging of a UNIX system, for its OS X core, Darwin, and in turn made Darwin freely available for modification and reuse. Apple's own developers work with other developers to enhance and fix what is now essentially a public enterprise.
Unlike earlier Macintosh operating systems, the Darwin core of OS X, provides preemptive multitasking rather than the less flexible time-slicing approach to multitasking and protected memory, which ensures that any application running will not be able to overlay the memory assigned to another application. Darwin also incorporates the Apache Web server and support for both Macintosh and UNIX file systems.
Darwin runs on Intel processor -based computers as well as PowerPC -based Macintosh computers. Apple expects that Darwin will eventually become the core of a completely separate open source operating system, similar to Linux .