This book reflects the current industrial interest and investment in process control systems. The use of computer systems in process control can provide great benefits, and it is estimated that efficiency can be increased by up to 30%. It is not surprising, therefore, that there have been considerable efforts by system designers and users to introduce and use such systems. Process hardware is integrated into a complete production system through data processing. It is for this purpose that technical specialists (eg electrical, mechanical, electronics, communication and process engineers and programmers) are involved in data processing. The scope of this book is therefore to assist in the selction of computer hardware and software that match the functional specification of the data processing component of a particular system.