This book presents a comprehensive treatment of signals and linear systems at an introductory level. The text emphasizes the physical appreciation of concepts rather than mere mathematical manipulation of symbols. Mathematics is used to enhance physical and intuitive understanding rather than to prove axiomatic theory. Theoretical results are frequently supported by carefully chosen examples and analogies. The organization of the book permits a great deal of flexibility in teaching the continuous-time and discrete-time concepts. The natural sequence of chapters is meant to integrate continuous-time and discrete-time analysis. It is also possible to use a sequential approach in which all the continuous-time analysis is covered first, followed by discrete-time analysis. Therefore, the book can adapt either of the most common approaches to teach signals and systems course.