The product is a revised edition of the textbook “Signals and Systems” by Alan Willsky, S. Nawab, and Alan Oppenheim. This comprehensive exploration of signals and systems covers both continuous-time and discrete-time concepts/methods in parallel, focusing on the similarities and differences between the two. It includes introductory treatments of applications in filtering, communication, sampling, and feedback. With a college audience in mind, this authoritative book provides a solid foundation and lifetime reference for anyone studying the most important methods of modern signal and system analysis. The major changes of the revision include reorganization of chapter material and the addition of a wider range of difficulties.