This paper proposes an analysis of the convergence of discrete differential equations obtained by Euler approximation methods. Backward and Feed-forward Euler approximations are considered. These kinds of methods are very often used in discretisation of continuous models because of their straightforward structure which allows an easy implementation in microprocessor applications. These two kinds of discretisations are very important in the representation of controllers in which the use of a fast algorithm of its discrete representation is a basic condition for the whole stability of the closed loop control structure.