In digital circuits the output of any circuit should not only depends on inputs of the circuit, in-addition to the inputs some sort of triggering mechanism should be provided for synchronized operation digital circuit which enables to provide a real time data at the output of the circuit.
Take a positive level triggered clock
If the clock is +ve level triggered then in other then +ve level output is not depend on input.
If the clock is +ve level triggered then only in this level output will be depend on input.
Based on the Triggred we can classified flip flop into four catogries.
For example if clock is +ve level Triggered then