Partial differential equations are more difficult to solve than ordinary differential equations. By a solution of a partial differential equation, we mean a function that satisfies the differential equation. A basic fact is that in general it is not possible to find closed-form formulas for solutions of partial differential equations To uniquely determine a solution, we often need to specify some supplementary conditions, called boundary value conditions or initial value conditions. This forms a partial differential equation problem an initial value problem, boundary value problem, or initial boundary value problem. Partial differential equation problems arising in applications are usually solved by numerical methods. Among the various numerical methods, the finite differ ence method is a general one that is easy to derive and to implement. In this chapter, we will study the finite difference method to numerically solve the model PDEs (9.1-9.3)