Android uses the Linux kernel, which began development in 1991. Mac OS X, iOS, and other Apple platforms are based on Unix, which originated at AT&T’s Bell Labs in 1969. Windows computers are based on the Windows NT kernel, which dates back to 1993.
http://www.fastcompany.com/3063006/why-on-earth-is-google-building-a-new-operating-system-from-scratch
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