With the presentation at an introductory level, this book contains a comprehensive treatment of continuous-time and discrete-time signals and systems using demos on the Web, data downloaded from the Web, and illustrations of numerous MATLAB commands for solving a wide range of problems arising in engineering and in other fields such as financial data analysis. The third edition is a major revision of the previous edition in that the extent of the use of mathematics has been greatly reduced, practical applications involving downloaded data and other illustrations have been added, and the material has been reorganized in a significant way so that the flexibility in using the book in a one-quarter or one-semester course should be greatly enhanced.