One of the most fundamental courses for electrical engineering students, specially communication and control engineering majors, is of course signals and systems. This course is all about basics of what signals and systems are, and how they are characterized and how can one deal with them systematically.After the general introduction to basics and definitions of signals and systems in chapter 1 and 2, gradually starts to build up the powerful tools of manipulating signals mathematically, tools like Fourier series and transform, and Laplace and Z-transform. There is also a very interesting chapter about sampling and modulation, chapter 5, which talks about how can one basically take samples from a continuous signal and prepare it for transmission, via modulation.