This book has been carefully prepared to address the needs of controller selection for any application. Chapter 1 deals on the definition of Process Control Engineering and the classification of process control systems. In chapter 2, engineering models of analog controllers are presented. Chapter 3 deals on digital controllers, real ¿ time control systems and types of automatic control systems. Since there¿s a relationship between analog controllers and analog computers, chapter 4 of the book is devoted to analog and hybrid computers. In chapter 5 of the book, reliability, a very important factor in any component/equipment, is meticulously and extensively treated. Chapter 6 of the book deals on the conventional flow chart and the Algorithmic State Machine, which are both tools used in process control engineering as well as in other areas of human endeavours. In order to drive home the several concepts expressed in the book, several real ¿ life questions, (and their answers), are presented in chapter 7 of the book. It is hoped that students and practitioners of control engineering will find the book a valuable companion.