PS/2 connector (PS/2 keyboards):
These were introduced with IBM's PS/2 computers and therefore are known as PS/2 connectors. They have 6-pins but actually their wiring is just a rearrangement of 5-pin DIN connector. This connector is smaller in size and quite popular these days. Because of the similar wiring a 5-pin DIN can simply be attached to a PS/2 connector by a simple adapter.