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XNU is the computer operating system kernel developed at Apple Inc. since December 1996 for use in the OS X operating system and released as free and open source software as part of the Darwin operating system. ''XNU'' is an acronym for ''X is Not Unix''. Originally developed by NeXT for the NeXTSTEP operating system, XNU was a hybrid kernel combining version 2.5 of the Mach kernel developed at Carnegie Mellon University with components from 4.3BSD and an Objective-C API for writing drivers called Driver Kit. After Apple acquired NeXT, the Mach component was upgraded to 3.0, the BSD components were upgraded with code from the FreeBSD project and the Driver Kit was replaced with a C++ API for writing drivers called I/O Kit. ==Kernel design== XNU is a hybrid kernel, containing features of both monolithic kernels and microkernels, attempting to make the best use of both technologies, such as the message passing capability of microkernels enabling greater modularity and larger portions of the OS to benefit from protected memory, as well as retaining the speed of monolithic kernels for certain critical tasks. Currently, XNU runs on ARM,〔(iPhone processor found: 620MHz ARM CPU ) (July 1, 2007 Retrieved January 6, 2008〕 IA-32, and x86-64 processors, both single processor and SMP models. PowerPC support is removed as of version 10 (i.e. Mac OS X 10.6). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「XNU」の詳細全文を読む スポンサード リンク
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