The mac started out without using extensions at all, the type was embedded in the metadata. That's still possible now, but it's largely derived from extensions first. I believe Finder shows all extensions by default. It certainly does in details mode.
replyMacs originally didn’t have filename extensions because the file type was stored as metadata in the file system
replyThat really is a superior way of doing things too. Or at least it would have been if that metadata were transferred with the file itself in all protocols.
reply