Question: how to identify iir and fir filters?
Answer: The easiest way to determine whether a filter is IIR or FIR is to identify its pole locations. For FIR filters, there is a rule for this that is based on the structure of the impulse response: If the system is causal (i.e. it is zero for all n<0), then it is FIR if all of its poles are located at the origin (z=0).