Mac OS X 10.5, which was part of the Intel transition, dropped support for classic applications entirely.
Mac OS X 10.4.11 was the last version to support the Classic environment, which was an optional installation item with Mac OS 9.2.2. When the first retail version of Mac OS X 10.0 was released in March 2001, the minimum version of classic Mac OS to be supported was 9.1, which was included as part of the installation. Another transition technology called Carbon was also introduced, which allowed applications which took advantage of the API to run on both Mac OS 9 and PowerPC versions of Mac OS X. Stability was inconsistent and improved with successive public beta releases. Any problematic legacy program that would normally cause Mac OS 9 to crash could be contained and only require relaunching of the Classic environment without bringing down the main system.ĭuring beta testing of Mac OS X, the minimum version of classic Mac OS to be supported was 9.0.4, which needed to be installed separately. During its early development under the code name Rhapsody, a proof-of-concept called ' Blue box' demonstrated that backwards compatibility could be provided through a native application that would run the older software in a sandbox environment. Mac OS X is based on NeXTSTEP, which uses a Unix-based kernel that is inherently incompatible with classic Mac applications.
