This book gives an account of the work by the author for Philips Research Eindhoven during 24 years as scientific employee and, after his retirement,33 years as guest thereof.The first 12 years he developed basic software for three different computersof the computing center of the laboratory. The description is partly of a technical nature but also tries to describe the motivations for the work done.The years after his retirement were mainly used to documenting previous work, but also lead to several publications.