The third edition os a major revision which includes three new chapters on network models, Markovian decision process, and queuing theory in practice. The exercises and problems have been enlarged, with the new problems adding new ideas and testing different aspects of the covered topics. The prime goal is to make the book more readable for the student. Without good understanding of linear programming theory, one can only acquire a superficial knowledge of such techniques as networks, integer programming, and nonlinear programming.