A black-box solver for the solution of general nonlinear functional equations by mixed FEM The authors present a strategy to compute the approximation of the exact solution of steady functional equations by the mixed finite element method (FEM) with low computational amount. The discretized functional equation is solved by the Newton-Raphson method. The problem for getting statements on the discretization error by involving an error indicator based on an inspection of the functional on a space different from the FEM space is discussed.par The idea has been realized in the FORTRAN 77 program package VECFEM for vector computers. An example for the computation of the velocity distribution and the pressure of a viscous incompressible flow (two-dimensional problem) through a channel with a barrier using an SNI/Fujitsu S600/20 computer is presented.