An equalizer that mitigates both linear and nonlinear distortions for amplitude phase keyed signals that are processed thereby. Algorithms employed in the equalizer are based on correcting received signals based on symbol transitions between successive symbols. The linear portion of the equalizer is programmable and can use any available algorithm. Programmable linear taps of the equalizer may be programmed in a nonlinear manner by using the lookup tables as amplitude dependent equalizers that are used to process one symbol at a time. In the equalizer, each amplitude level has it's own correction factor by using amplitude dependent coefficients. The equalizer can implement both linear and nonlinear equalization. Equalizer corrections are implemented using predetermined values stored in lookup tables. The equalization corrections are determined in an external computer and are loaded into the lookup tables for each amplitude level of the received signals. The equalizer is programmable and may be used with any amplitude phase keyed signal by reprogramming the lookup tables from the external computer for the desired modulation.