Memory less system
A system is memoryless if for any $ t\in \mathbb{R} $ only on the input at $ t_0, $
Eg:
Y(t) = X(t) + X(t-1){ memoryless}
Y(t) = X(t)+X(t-1) { with memory}.
Invertible systems
A system is invertible if distinct inputs yield distinct outputs.
Eg:
Y(t) = 2x(t) + 3.
Causalty
A system is called causal if output at any given time only depends on input in present and past(not future)ie; for any time $ t_0, $
Y($ t_0, $) only depends on X(t) with t<$ t_0, $
Y(t) = X(t+1) {non causal}
Y(t) = X(t-1){causal}
