Numerical calculation of electrostatic fields with potentials given within the area of calculation

Contents The numerical calculation of two-dimensional fields with the finite-difference-method leads to a system of equations with a symmetrical matrix of coefficients. In case of given potentials within the area of calculation the matrix of coefficients is banded with five diagonals, but with changing bandwidth. Compared with common methods here another method is introduced that keeps the bandwidth constant and simplifies the programming. Some examples show that this method is also much faster than others.