IEC 1131-3 is the international standard for the design of software for industrial control systems. It defines a set of related graphical and textual languages that bring significant benefits throughout the control system life-cycle - benefits for system integrators, control system engineers and end-users alike. The standard marks the beginning for wellstructured, re-usable and maintainable software for industrial control systems. This new edition has been revised and updated to include all IEC proposed amendments and corrections for the planned 1999 edition of IEC 1131-3, agreed by the IEC working group in spring 1998. The book now includes IEC 1131-3 'frequently asked questions' and a summary of future developments influencing the next generation of PLC languages, plus an overview of IEC 1499 standard on function blocks. Although primarily for programmable logic controllers (PLCs), IEC 1131-3 concepts will also influence the design of software for fieldbus devices. This book introduces all the concepts of the IEC 1131-3 standard and provides examples of the languages related typical industrial control problems. It will be of interest to everyone involved in specifying or developing software for industrial or manufacturing applications. The text will also be of value to students and engineers with a general interest in new techniques for industrial or manufacturing applications. The text will also be of value to students and engineers with a general interest in new techniques for industrial control systems.