Apple Launches OS X v10.0, Codenamed "Cheetah"
Mac OS X version 10.0, code named “Cheetah”, is the first major release of Mac OS X, Apple’s desktop and server operating system.
Mac OS X v10.0 was released on March 24, 2001 for a price of US$129. It superseded the Mac OS X Public Beta and preceded Mac OS X v10.1.
Mac OS X v10.0 was a radical departure from the previous “classic” Macintosh operating system and was Apple’s long awaited answer to the call for a next generation Macintosh operating system. It introduced a brand new code base completely separate from Mac OS 9's, as well as all previous Apple operating systems. Mac OS X introduced the new Darwin Unix-like core and a totally new system of memory management. It proved to be a rocky start to the Mac OS X line, plagued with missing features and performance issues, although it was praised for being a good start to an operating system still in its infancy, in terms of completeness and overall operating system stability.
OS 10.0 "Cheetah" Released March 24, 2001, the first consumer version of OS X left the Classic Mac OS in the dust—though much like Rosetta eased the transition to Intel processors, the Classic environment allowed you to still run older Mac apps. Cheetah introduced the Aqua interface, the Dock, and Mail. But it was also unstable, sluggish (blasphemy in the current Apple canon), and hardware didn't "just work." Put another way: It was bad enough 10.1 was released as a free upgrade less than 8 months later.