A difference-routing digital filter (d.r.d.f.) consists of a transversal filter cascaded with an undamped digital resonator. Complicated multiplication operations are avoided by restricting all coefficients to small integers. A new set of resonator structures, which in many cases offers substantial improvements over existing designs, is first described. The real-time implementation of the resulting filters on standard 16-bit mini-and microcomputers is then considered. A wide range of filter characteristics may be programmed at sampling rates up to a few kilohertz.