Although it is hardly possible to keep up with advances in technology, it is reassuring to know that in science
and engineering, development and innovation are possible through a solid understanding of basic principles.
The theory of signals and systems is one of those fundamentals, and it will be the foundation of much research
and development in engineering for years to come. Not only engineers will need to know about signals and
systems—to some degree everybody will. The pervasiveness of computers, cell phones, digital recording, and
digital communications will require it.
Learning as well as teaching signals and systems is complicated by the combination of mathematical abstraction
and concrete engineering applications. Mathematical sophistication and maturity in engineering are needed.
Thus, a course in signals and systems needs to be designed to nurture the students’ interest in applications,
but also to make them appreciate the significance of the mathematical tools. In writing this textbook, as in
teaching this material for many years, the author has found it practical to follow Einstein’s recommendation
that “Everything should be made as simple as possible, but not simpler,” and Melzak’s  dictum that “It is
downright sinful to teach the abstract before the concrete.” The aim of this textbook is to serve the students’
needs in learning signals and systems theory as well as to facilitate the teaching of the material for faculty by
proposing an approach that the author has found effective in his own teaching.
We consider the use of MATLAB, an essential tool in the practice of engineering, of great significance in the learning
process. It not only helps to illustrate the theoretical results but makes students aware of the computational
issues that engineers face in implementing them. Some familiarity with MATLAB is beneficial but not required.