Numerical Analysis is an interdisciplinary topic which develops its strength only when viewed in close connection with applications. Nowadays, mechanical engineers having computer simulation as a daily engineering tool have to learn more and more techniques from that field. Mathematicians, on the other hand, are increasingly confronted with the need for developing special purpose methods and codes. This requires a broad interdisciplinary understanding and a sense for model-method interactions. With this monograph we give an introduction to selected topics of Numerical Anal­ ysis based on these facts. We dedicate our presentations to an interesting discipline in computational engineering: multibody dynamics. Though the basic ideas and methods apply to other engineering fields too, we emphasize on having one homo­ geneous class of applications. Both authors worked through many years in teams developing multibody codes. Interdisciplinary work also includes transferring ideas from one field to the other and a big amount of teaching -and that was the idea of this book. This book is intended for students of mathematics, engineering and computer sci­ ence, as well as for people already concerned with the solution of related topics in university and industry. After a short introduction to multibody systems and the mathematical formulation of the equations of motion, different numerical methods used to solve simulation tasks are presented. The presentation is supported by a simple model of a truck. This truck model will follow the reader from the title page to the appendix in various versions, specially adapted to the topics.