# Translations:Appendix K: Exercises/62/en

60. Discuss FIR and IIR filters. [Answer: Filters categorized as FIR (finite-impulse-response) filters are absolutely stable but often require many points for accurate design. One disadvantage with them is the many multiplications and additions required in their application. Another disadvantage is that the filter can reach into areas far from its center and thus be more prone to noise and extraneous signals. The *Z*-transform of an IIR (infinite-impulse-response) filter is the quotient of two polynomials. Such filters are more flexible in design than FIR filters are, and in addition they require fewer multiplications and additions than do comparable FIR filters. However, an IIR filter is not as easy to design as a FIR filter is. Moreover, an IIR filter is susceptible to errors that can produce instability in that the output can oscillate or grow without limit.]