In this paper, the application of the explicit M.R.A.C. algorithms to the D.C. motor speed control using the microprocessor is studied. The adaptation algorithms are derived from the gradient method and the exponentially weighted least square [E.W.L.S.] method. In order to minimize the computational instability of the E.W.L.S. method, the adaptation algorithm of UDUt factorization method is developed, and because of the characteristics of the D.C. motor (dead-aone phenomenon) , the SM. gra-dient type algorithm is also improved from the gradient type algorithm. Computer simulations and experiments show that these algorithms adapt well to the rapid change of the reference input and the load.