I am sure everyone here knows that Mac OS made the transition to its own, native filesystem, dubbed "APFS", around the release of iOS 10.
However, it is also commonly known that behind the scenes Darwin (UNIX) is employed for standard libraries, filesystems, and other low-level system services that I have not looked into.
My question is how Apple managed to create seemingly fluid interactions between the longstanding UNIX filesystem and the newer APFS (which, not to mention, has 64-bit inode numbers). Thank you.
Are you talking about storing resource forks? There is a section in the wikipedia entry for resource forks on this:
https://en.wikipedia.org/wiki/Resource_fork#Compatibility_problems