System that operate under real-time conditions need to be causal hat is they can only process present an past inputs. When no real time processing is needed the system can be noncausal. Consider the case of averaging an input signal x(n) uner real time conditions. suppose you are given two different filters
y{n}= 1/n *(symbol of Sum) x(n-k) on top N-1 at bottom k=0
y{n}= 1/n* (symbol of Sum) x(n-k) on top N-1 at bottom k=-N+1
which one of this will be use and why?