(in lingua inglese)
In this paper an exponentially fitted tridiagonal finite difference method is presented for solving boundary value problems for singularly perturbed differential–difference equations containing a small negative shift. The method is developed for problems with shift parameter smaller than the perturbation parameter. The method is shown to have almost second order parameter uniform convergence. An extensive amount of computational work has been carried out to demonstrate the proposed method and to show the effect of shift parameter on the boundary layer behaviour of the solution.