Mac OS X "Cheetah" (10.0)
Reign: March 2001-September 2001
Key new capabilities: First Mac OS to be based on Next's NextStep rather than the original "classic" Mac OS
Notes: Cheetah was considered a slow, incomplete product and gained little adoption, but it was Apple's first realized attempt to reinvent Mac OS after five years of failed attempts. It was based on Mac OS X Server, released in late 1999, as a version of Unix with a modest graphics front end and heavy reliance on Web-based access to server tools.