What happen to a dff(flip flop) without input?
After the asynchronous reset is deasserted and the first rising clock edge occurs, the flip-flop's state will generally be indeterminate. The only way the state could have a known value is if the flip-flop's inputs have a known value when they are unconnected, due to the specific circuitry involved. For example, true TTL logic inputs would default to a high logic level if left unconnected.