Given the following State graphs for two sequential machines

Given the following State graphs for two sequential machines. The first graph represents a correctly functioning machine, and the second represents the same machine with a malfunction. Assuming that the two machines can be reset to their starting states (S0 and T0), determine the shortest input sequence that will distinguish the two machines.

Solution

     The machines are exactly the same in the first three states (S0 and T0, S1 and T1, S2 and T2) but in the fourth state there is a difference.

     In the first machine: State \'S3\' goes to state \'S2\' with input/output = 1/0 (one input and one output).

     In the second machine: State \'T3\' remains stable in state \'T3\' with input/output = 1/0 (one input and one output).

     Shortest input sequence that will distinguish the two machines: Input = 0 0 0 1