XNU is the computer
operating system An operating system (OS) is system software System software is software designed to provide a platform for other software. Examples of system software include operating systems like macOS macOS (; previously Mac OS X and later ...

operating system
kernel Kernel may refer to: Computing * Kernel (operating system) In an operating system with a Abstraction layer, layered architecture, the kernel is the lowest level, has complete control of the hardware and is always in memory. In some systems it ...
developed at
Apple Inc. Apple Inc. is an American multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational force, a military body from multiple countries * Multinational state, a ...
since December 1996 for use in the Mac OS X (now
macOS macOS (; previously Mac OS X and later OS X) is a proprietary {{Short pages monitor