Programmable Controllers: An Engineer's Guide by E. A. Parr, third edition, is a thorough practical book on PLCs for control engineers and technicians. It explains the background of computers and logic in industrial control, PLC hardware, inputs and outputs, and the main programming methods: ladder logic, instruction lists, function blocks, sequential function charts and structured text according to IEC 61131. Further chapters cover analog signals and closed loop control, communications and industrial networks, SCADA and operator interfaces, program design, documentation, safety, commissioning and fault finding. Written by an experienced engineer with many real examples from different PLC manufacturers, it bridges theory and plant practice.