This book contains a comprehensive introductory treatment of continuous-time and discrete-time signals and systems with numerous illustrations using MATLAB, data downloaded from the Web, and online demos on the textbook website. The book is intended for use in a one-semester or one-quarter course at the sophomore or junior level. Highlights of the revised content of the third edition include the following. The presentation has been simplified by deleting or rewriting various mathematical parts of the previous edition and by providing new illustrations that give additional insight into the meaning and significance of the mathematical formulations covered in the text. Summaries have been added at the end of the chapters to highlight the material covered. The core of the new edition consists of Chapters 1-7, most of which an instructor should be able to cover in a one-quarter course. For a one-semester course, an instructor should be able to cover most of the material in Chapters 1-7 and then select material on filtering, controls, and/or the state representation, which can be found in Chapters 8-11. The new edition contains practical applications that use actual data that is downloaded from the Web. It is shown how the data can be downloaded and then imported into MATLAB for analysis using techniques covered in the text. The focus is on the problem of data analysis in the presence of noise, which often arises in engineering, business and finance, and other fields. The new edition contains a major enhancement of the MATLAB component. In particular, the MATLAB Symbolic Math Toolbox that is available in the Student Version (7.0.1) of MATLAB is used throughout the text to complement and simplify various computational aspects of the theory and examples given in the book. Simulink is also used for building system models and simulating system behavior. The textbook website (http://users.ece.gatech.edu/[tilde]bonnie/book3) has been updated with the inclusion of additional worked problems and the addition of all the data files and M-files for the third edition. Book jacket.