Synthetic aperture radar (SAR) and inverse synthetic aperture radar (ISAR) are enhanced resolution imaging radar systems. These systems receive coherent radar signal returns from an illuminated scene and use the signal modulation related to terrain reflectivity and relative motion between the scene and the observation platform to form an image of the scene. The extraction, storage, and coherent processing of these modulation terms represent an enormous signal processing task which classically has been performed by optical techniques. The flexibility and reduced cost of modern high performance, high bandwidth digital signal processing systems is the motivation for full DSP based imaging radar systems. In this paper we review the common DSP tasks performed by basic SAR and ISAR imaging radars.