This book introduces basic traditional semiotic concepts and adapts them so that they become useful for analyzing and designing computer systems in their symbolic context of work. It presents a novel approach to the subject, rich in examples, and is theoretically systematic but practical. The author refers to and reinterprets techniques already used, so that readers can deepen their understanding. In addition, it offers new techniques and a consistent perspective on computer systems that is particularly appropriate for new hardware and software whose main functions are presentation and communication. This book will benefit all involved in the development of systems in which meaning and interpretation are vital.