This book is based on the lectures given at a Vacation School for postgraduate students in the areas of Control and Instrumentation held at the University of Sheffield in March 1990. The course had four major themes, design and tuning of controllers, the hardware technology, software design and examples of applications. The first of the themes, design and tuning of controllers, is covered in chapters 1-4. In chapter 1, Leigh covers discrete controller design for single-loop systems and in chapter 2 Virk deals with the design of controllers for multivariable systems. Methods of automatic tuning for commercial PID controllers are surveyed by Gawthrop in chapter 3 and in chapter 4 practical aspects of implementing and tuning PID controllers are discussed by Smith.