This text introduces computational and mathematical techniques for modeling, simulating, and analyzing the performance of various systems. Its goal is to help students gain a better understanding of how systems operate and respond to change by: 1) helping them begin to model, simulate, and analyze simple-but- representative systems as soon as possible; and 2) whenever possible, encourage the experimental exploration and self-discovery of theoretical results before their formal presentation. The authors' approachable writing style emphasizes concepts and insight without sacrificing rigor.