This chapter constitutes an introduction to linear multi step methods, Runge Kutta
methods, and finite difference methods which are presented in the chapters that follow. The homo-
geneous and non-homogeneous linear difference equations are solved by the following Mathematica
modulae: The module differenceEqn finds the general solution of a linear difference equation, the
module baseSolution finds the fundamental set of solutions of a homogeneous linear difference equa-
tion, the module particularSolution finds a particular solution of a non-homogeneous linear difference
equation by the method of variation of coefficients. The chapter ends with a set of questions.