Mac OS X, Apple's Unix-based operating system for Macintosh computers, later renamed macOS.
Acronym standing for Operating System X, where X represents the Roman numeral ten. Released in 2001 as Apple's successor to Mac OS 9, built on the NeXT operating system foundation.
OS X marked Apple's radical departure from their previous operating system by adopting Unix foundations, which meant incorporating decades of stability and security from academic and server environments into a consumer-friendly interface. The 'X' wasn't just version ten - it symbolized a complete reinvention.
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