As I understand, after Prof. Dippet retired it was the transfiguaration teacher Prof. Dumbledore who became Headmaster of Hogwarts. During the course of the Harry Potter books we see that Prof. McGonagall is the deputy headmistress and the transfiguration teacher. This would mean that Prof. Dumbledore now doesn't hold that teaching position anymore.
So what exactly does a Hogwarts Headmaster/Headmistress do?
Naturally they would appoint teachers and have some amount of administration work including the sending out of letters of acceptance to Hogwarts but what (if anything) else? Don't they have to teach?
EDIT : I get that Dumbledore had many duties being chief Warlock of the Wizemgamot etc., but is there any evidence that all previous Heads had similar duties? I was asking about a Head of Hogwarts in general, not just Dumbledore.