This third edition of Discrete-Time Signal Processing is a descendent of our original textbook Digital Signal Processing published in 1975. That very successful text appeared at a time when the field was young and just beginning to develop rapidly. At that time the topic was taught only at the graduate level and at only a very few schools. Our 1975 text was designed for such courses. It is still in print and is still used successfully at a number of schools in the United States and internationally. By the 1980´s, the pace of signal processing research, applications and implementation technology made it clear that digital signal processing (DSP) would realize and exceed the potential that had been evident in the 1970´s. The burgeoning importance of DSP clearly justified a revision and updating of the original text. In organizing that revision, it was clear that so many changes had occurred both in the field and in the level and style with which the topic was taught, that it was most appropriate to develop a new textbook, strongly based on our original text, while keeping the original text in print. Whe titled the new book, published in 1989, discrete-Time Signal Processing to emphasize that most of the DSP theory and design techniques discussed in the text apply to descrete-time systems in general, whether analog or digital.