Editing XNU (section)

{{Short description|Computer operating system kernel}}
{{Use mdy dates|date=October 2013}}
{{Not to be confused with|GNU}}{{Infobox OS
| name = XNU
| logo = <!-- Filename only: no wikilink, no Image: or File: -->
| logo caption = 
| logo size = 
| logo alt = 
| screenshot = The XNU Kernel Graphic.svg
| caption = The XNU kernel
| screenshot_size = 
| screenshot_alt = 
| collapsible = 
| developer = [[Apple Inc.]]
| family = [[Unix-like]], [[Unix]]<ref>https://www.opengroup.org/openbrand/register/index2.html</ref>
| working state = Current
| source model = [[Open-source software|Open-source]]
| released = {{Start date and age|1996|12}}
| latest release version = 
| latest release date = <!-- {{Start date and age|202y|mm|dd}} -->
| latest preview version = 
| latest preview date = <!-- {{Start date and age|202y|mm|dd}} -->
| marketing target = 
| programmed in = [[C (programming language)|C]], [[C++]]
| update model = <!-- APT, etc. -->
| package manager = <!-- dpkg, rpm, etc. -->
| supported_platforms = Current: [[x86-64]], [[AArch64|64-bit ARM]], [[ARM architecture#32-bit architecture|32-bit ARM]] (32-bit ARM support is closed-source)<br />Historical: [[PowerPC]] (32-bit and 64-bit), [[IA-32]]
| kernel type = [[Hybrid kernel|Hybrid]]
| userland = 
| ui = 
| license = [[Apple Public Source License]] 2.0
| preceded by = [[Mach (kernel)|Mach]], [[Nukernel]]
| succeeded by = 
| website = {{URL|github.com/apple-oss-distributions/xnu}}
| other articles = 
}}

'''XNU''' ("X is Not Unix") is the computer [[operating system]] (OS) [[Kernel (operating system)|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 (operating system)|Darwin]] OS, which, in addition to being the basis for macOS, is also the basis for [[Apple TV Software]], [[iOS]], [[iPadOS]], [[watchOS]], [[visionOS]], and [[tvOS]].<ref>{{cite web |year=2005 |url=https://developer.apple.com/library/content/documentation/Porting/Conceptual/PortingUnix/glossary/glossary.html |title=Porting UNIX/Linux Applications to Mac OS X: Glossary |publisher=Apple Computer |access-date=June 7, 2017}}</ref>

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)|Mach kernel]] developed at [[Carnegie Mellon University]], which incorporated the bulk of the [[History of the Berkeley Software Distribution#4.3BSD|4.3BSD]] kernel modified to run atop Mach primitives, along with an [[application programming interface]] (API) in [[Objective-C]] for writing drivers named DriverKit.<ref>{{cite web |url=https://github.com/apple/darwin-xnu |title=XNU GitHub source code README|website=[[GitHub]]|date=December 16, 2021}}</ref>

After Apple acquired NeXT, the kernel was updated with code derived from [[OSFMK]] 7.3 from [[Open Software Foundation|OSF]],<ref name="wwdc-2000-session-106">{{cite AV media|url=https://www.youtube.com/watch?v=ggnFoDqzGMU |archive-url=https://ghostarchive.org/varchive/youtube/20211221/ggnFoDqzGMU |archive-date=2021-12-21 |url-status=live|last=Magee |first=Jim |title=WWDC 2000 Session 106 – Mac OS X: Kernel|minutes=14}}{{cbignore}}</ref> and the [[FreeBSD]] project, and the DriverKit was replaced with new API on a restricted subset of [[C++]]<ref>{{cite web|url=https://developer.apple.com/library/mac/documentation/DeviceDrivers/Conceptual/WritingDeviceDriver/CPluPlusRuntime/CPlusPlusRuntime.html#//apple_ref/doc/uid/TP30000695-BAJIBFDE|title=The libkern C++ Runtime|work=IOKit Device Driver Design Guidelines
}}</ref> (based on [[Embedded C++]])<ref>{{cite web|url=http://osxbook.com/book/bonus/ancient/whatismacosx/arch_xnu.html|title=What is Mac OS X?|author=Amit Singh|access-date=2015-03-04|archive-date=2019-04-19|archive-url=https://web.archive.org/web/20190419152142/http://osxbook.com/book/bonus/ancient/whatismacosx/arch_xnu.html|url-status=dead}}</ref> named IOKit.

By keeping the BSD kernel into the third part of XNU,<ref>{{Cite web |date=2011-08-08 |title=How Mac OS X Works |url=https://computer.howstuffworks.com/macs/mac-os-x2.htm |access-date=2025-03-12 |website=HowStuffWorks |language=en-us}}</ref> XNU became UNIX-based when macOS achieved UNIX certification under the Single UNIX Specification (SUS) by The Open Group.<ref>{{Cite web |last=McKay |first=Dave |date=2019-10-21 |title=Is macOS UNIX? (and What Does That Mean?) |url=https://www.howtogeek.com/441599/is-macos-unix-and-what-does-that-mean/ |access-date=2025-03-12 |website=How-To Geek |language=en}}</ref> Despite this, Apple retained the original 'XNU' name, which stands for 'X is Not Unix,' a relic from its NeXTSTEP origins before macOS was UNIX-certified. This has led to confusion, as the name suggests that XNU is separate from UNIX, even though macOS, as a whole, is officially recognized as a UNIX operating system.<ref>{{Cite news |title=Apple macOS 15 Sequoia is officially UNIX |url=https://www.theregister.com/2024/10/11/macos_15_is_unix/ |archive-url=http://web.archive.org/web/20250124104637/https://www.theregister.com/2024/10/11/macos_15_is_unix/ |archive-date=2025-01-24 |access-date=2025-03-12 |language=en}}</ref>