Consider the IBVP
If N interior grid points are used, then and , . If we select the explicit method Eq. 21, a complete set of FDEs for the example IBVP is
Note how the boundary conditions are incorporated into the n = 0 and n = N+1 difference equations. In a computer program the difference equations can be dealt with in a single loop if arrays holding U are dimensioned large enough to admit a 0-index and an -index with zero boundary conditions stored in these positions.