The state diagram shown up corresponds to a circuit implemen

The state diagram shown up corresponds to a circuit implementation that has two inputs: clock and F and uses four flip-flops with outputs D, C, B, A. The circuit implemented may well corresponds to a: Four bits right/left shift register

Solution

Answer is Modulo 16 UP/DOWN Counter

It counts from 0 to 15 in both UP and DOWN.

if F=0 , It counts from 0 to 15

if F=1 , It counts from 15 to 0