This text has been superseded by the FOURTH EDITION which includes a comprehensive discussion on window functions and examples using the fft and ifft MATLAB functions. As in previous editions, this text is an introduction to continuous and discrete-time signals and systems. It contains numerous examples that are solved analytically and verified with the latest Student Versions of MATLAB. It is intended for electrical engineering majors. It can also be used for self-study. Freshman-level calculus and some elementary knowledge of differential equations is assumed. An introduction to MATLAB, Simulink, review of complex algebra, and matrices and determinants, are discussed in Appendices A, B, and C, and D respectively.