This book is devoted to the influence of parametric perturbations and uncertainties on the Lyapunov exponents of discrete linear systems with timevarying coefficients. Different types of perturbations are considered, limited in terms of certain norms, tending to zero with a specified rate. For each of them, we describe their impact on the values of Lyapunov exponents. Results of such considerations, as presented in this book, while being widely known for stationary systems, are new and original when referred to the systems with variable coefficients. The book is addressed primarily to persons interested in the theory of Lyapunov exponents, which well characterize the behavior of the trajectory of time-varying systems. It is also important that the results of this work can be used by graduate students and researchers in new areas of research in dynamics of discrete systems. Analysis of discrete-time systems is also important from cognitive point of view and well established part of control theory and applied computer science.