Build list legend
|Version of Mac OS|
Mac OS 9 is the final incarnation of the classic "Mac OS". Codenamed Sonata for its initial revision, it boasted many new Internet-based features. OS 9, like its predecessors, lacked protected memory and full pre-emptive multitasking. Development of Mac OS 9 ceased during 2001. The final updates are fixes for compatibility issues with the "Classic" environment.