Computer Simulations belong to the most important methods for the theoretical investigation of granular materials. The present book is intended to serve as an introduction to the field. Accordingly emphasis is on a general understanding of the subject rather than on the presentation of latest advances in numerical algorithms. For the understanding of the numerical methods and algorithms basic knowledge of C++ is needed, however the text has been kept accessible also for readers who, eventually, prefer a different programming language. While the book is more on models than on the physics of granular material, many aplications to real systems are presented.