On Apple ][ (/e, /c, etc.) there was some non-standard DOS version (I don't think it was ProDOS, but something else) that was first geared towards using the 80

On Apple ][ (/e, /c, etc.) there was some non-standard DOS version (I don't think it was ProDOS, but something else) that was first geared towards using the 80 column mode (PR#3), but then it had the notion of directories.... but it was still storing everything in one big "flat" list, though each "file/dir" would have a parent index, so "cd someDir" and then "dir" would (I guess) just allow files that have in their parent_id as that dir. But after all, that's how you did any kind of "pointer" programming in language without pointers (like Apple Basic which was my first language) - you'll store things in array, and use indices (much like Databases)... Maybe it's somewhere in archive.org...