This fourth edition of Programmable Logic Controllers continues to provide an up-to-date introduction to all aspects of PLC programming, installation, and maintaining procedures. No previous knowledge of PLC systems or programming is assumed. As one reviewer of this edition put it "I honestly believe that someone with little or no background to PLC systems could take this book and teach themselves PLCs". Frank D. Petruzella has extensive practical experience in the electrical control field, as well as many years experience teaching and authoring textbooks. Before becoming a full time educator, he was employed as an apprentice and electrician in areas of electrical installation and maintenance. He holds a Master of Science degree from Niagara University, a Bachelor of Science degree from the State University of New York College - Buffalo, as well as diplomas in Electrical Power and Electronics from the Erie County Technical Institute.