Mac OS X 10.0 was a radical departure from the classic Mac OS and was Apple's long-awaited answer 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, and had a new Unix-like core, Darwin, which features a new memory management system. Unlike releases of Mac OS X 10.2 to 10.8, the operating system was not externally marketed with the name of a big cat.