Apple's OSX10 is a 13 year old
It's been 13 years since Apple first introduced it's new Unix based System 10, now a teenager but as mature as a middle aged stalwart dedicated to the Macintosh computer.
It's predecessor, System 9, was so heavily dependent on extensions, with users prodding around system files and Extension Manager to try and optimise the system for their programs. System 9 was also plagued with regular crashes. System 10 was an adjustment for users, either lapping up the simplicity or objecting to the lack of system control.
Sysyem 10, OSX, is the most successful operating system for Apple, and will be around for a while yet.