How to use the cd-index

A good way to study a polytope is through its cd-index. This invariant efficiently records the flag structure of a polytope, and can be defined for a broad class of posets. The Betti numbers and the Poincar\'e polynomial of such a poset can be readily extracted from the cd-index. We will show how to compute the cd-index by hand or with a computer and how to extract useful information from it.