A Core az a CPU (Core Duo), a Carbon meg a GUI. Nem vagyok OSX expert, de legjobb tudomásom szerint a Carbont használta az első N db OSX és a Cocoa az csak később lett bevezetve. Idézet a wikiből:
Carbon was one of two primary C-based application programming interfaces (APIs) developed by Apple for the macOS (formerly Mac OS X and OS X) operating system. Carbon provided a good degree of backward compatibility for programs that ran on Mac OS 8 and 9. Developers could use the Carbon APIs to port (“carbonize”) their “classic” Mac applications and software to the Mac OS X platform with little effort, compared to porting the app to the entirely different Cocoa system, which originated in OPENSTEP.
In order to offer a real and well supported upgrade path for existing Mac OS code bases, Apple introduced the Carbon system. Carbon consists of many libraries and functions that offer a Mac-like API, but running on top of the underlying Unix-like OS, rather than a copy of the Mac OS running in emulation. The Carbon libraries are extensively cleaned up, modernized and better "protected". While the Mac OS was filled with APIs that shared memory to pass data, under Carbon all such access was re-implemented using accessor subroutines on opaque data types. This allowed Carbon to support true multitasking and memory protection, features Mac developers had been requesting for a decade. Other changes from the pre-existing API removed features which were conceptually incompatible with Mac OS X, or simply obsolete. For example, applications could no longer install interrupt handlers or device drivers.A tévedés jogát fenntartom, nem vagyok OSX expert.