XNU
XNU (X is Not Unix) is the computer operating system (OS) kernel developed at Apple Inc. since December 1996 for use in the Mac OS X (now macOS) operating system and released as free and open-source software as part of the Darwin OS, which in addition to macOS is also the basis for the Apple TV Software, iOS, iPadOS, watchOS, visionOS, and tvOS OSes.
The XNU kernel | |
| Developer | Apple Inc. |
|---|---|
| Written in | C, C++ |
| OS family | Unix-like, Unix |
| Working state | Current |
| Source model | Open-source |
| Initial release | December 1996 |
| Repository | |
| Platforms | Current: x86-64, 64-bit ARM, 32-bit ARM (32-bit ARM support is closed-source) Historical: PowerPC (32-bit and 64-bit), IA-32 |
| Kernel type | Hybrid |
| License | Apple Public Source License 2.0 |
| Preceded by | Mach, Nukernel |
| Official website | github |
XNU was originally developed by NeXT for the NeXTSTEP operating system. It was a hybrid kernel derived from version 2.5 of the Mach kernel developed at Carnegie Mellon University, which incorporated the bulk of the 4.3BSD kernel modified to run atop Mach primitives, along with an application programming interface (API) in Objective-C for writing drivers named Driver Kit.
After Apple acquired NeXT, the kernel was updated with code derived from OSFMK 7.3 from OSF, and the FreeBSD project, and the Driver Kit was replaced with new API on a restricted subset of C++ (based on Embedded C++) named I/O Kit.