The book contains an introductory, yet comprehensive, treatment of continuous time and discrete-time signal and systems with demos on the Web and MATLAB examples integrated throughout the text. The second edition contains modifications of the material in the first edition to improve the presentation, additional illustrative examples and homework problems, a new chapter on communication systems, and the use of numerous on-line demos that illustrate the concepts and techniques presented in the book. The chapter on communications covers both analog and digital modulation with an emphasis on the digital case, including phase-shift keying, frequency-shift keying, quadrature amplitude modulation, and on-off keying.