The module uses concepts of application design to structure the presentation of C++ and numerical material. As new ideas are introduced their realisations in C++ are presented in the context of applications of numerical methods to models of asset pricing. The chief example is a simulation method. This is developed from a naive monolithic single procedure main to a powerful fully polymorphic application. The final application, employing a variety of important design patterns including a polymorphic factory, uses most of the syntactical elements of C++ in standard design paradigms. Other examples include evolution of Arrow-Debreu prices in a lattice.