Discrete dynamical systems, the main topic of this book, have had a fast development due to the development of computer science. Programming an iteration with the form xn+1 = f(xn), where f is a real function is made easy with modern computers. So, with the modern computer, it is relatively easy and fast to obtain simulations related with the dynamics of their models. Finding analytical proofs for computer simulations of models are natural and exciting problems for mathematicians and, like in a feedback process, new powerful analytical results motivate the use of discrete models. This new book examines the theory of dynamical systems.