The purpose of this paper is to establish a guide for the employment of a digital differential analyzer (DDA) as a control element. An analysis of the performance limitations imposed by a fixed point scaling procedure is presented in terms of bandwidth and a canonical realization for transfer functions. Roughly, the results are that for a DDA of

iterations/s and for a resolution of one part in q
-1: 1) the bandwidth is

rad/s 2) the poles of

must lie in a circle of radius

about

3) the significant poles of

must lie in a circle of radius

about

.