Mac OS X 10.0

Mac OS X 10.0 (code named Cheetah) is the first major release and version of macOS, Apple's desktop and server operating system. Mac OS X 10.0 was released on March 24, 2001 for a price of US$129. It was the successor of the Mac OS X Public Beta and the predecessor of Mac OS X 10.1 (code named Puma).
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.
Multilingual snags.
Mac OS X 10.0 began a short era (that ended with Mac OS X 10.2 Jaguar's release) where Apple offered two types of installation CDs: 1Z and 2Z CDs. The difference in the two lay in the extent of multilingual support.
Input method editors of Simplified Chinese, Traditional Chinese, and Korean were only included with the 2Z CDs. They also came with more languages (the full set of 15 languages), whereas the 1Z CDs came only with about eight languages and could not actually display simplified Chinese, traditional Chinese and/or Korean (except for the Chinese characters present in Japanese Kanji). A variant of 2Z CDs were introduced when Mac OS X v10.0.3 was released to the Asian market (this variant could not be upgraded to version 10.0.4). The brief period of multilingual confusion ended with the release of v10.2. Currently, all Mac OS X installer CDs and preinstallations include the full set of 15 languages and full multilingual compatibility.