Mac OS or Macintosh Operating System is not based on Linux. Rather it is based on Darwin which is an open-source OS based on UNIX. This Darwin OS contains the code from Apple, then some from NeXTSTEP (NeXT’s OS, discontinued), BSD, Mach, and some other free software projects. Mac OS along with iOS, tvOS, iPadOS, and watchOS are based on Darwin derived from UNIX.
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