The basic CLP model class hierarchy is simple. The top three levels of the hierarchy are depicted in the figure below. The first two levels (i.e. ClpModel, ClpSimplex, ClpInterior) contain all the problem data which define a model (that is, a problem instance). The third level contains most of the algorithmic aspects of CLP. There is a fourth level (for models with more general objectives than linear ones), but a description of it is beyond the current scope of this document.

Most Simplex users need only concern themselves with the classes ClpModel and ClpSimplex. There are algorithm-specific classes which inherit from ClpSimplex (e.g. ClpSimplexDual and ClpSimplexPrimal), but they have no member data and rarely need be visible to the user. These classes are cast at algorithm time. So, for example, after instantiating an object model of type ClpSimplex, a user only need call model.dual() to invoke the dual simplex method.