A system is said to possess memory if its output signal depends on past or future values of the input signal.A system is said to possess memoryless if its output signal depends only on the present values of the input signal.A system is said to be causal if its present value of the output signal depends only on the present or past values of the input signal.A system is said to be noncausal if its output signal depends on one or more future values of the input signal.