Chapter 1: What is a Programmable Logic Controller (PLC)? Table of Contents Purpose and Perspective of the Chapter............................................................................... 1 Chapter Objectives............................................................................................................. 1 What’s New in This Chapter................................................................................................ 1 Review Questions............................................................................................................... 2 Answers to Review Questions.............................................................................................. 2 Purpose and Perspective of the Chapter The purpose of this chapter is to give students a general overview of what a programmable logic controller (PLC) is and how it differs from a computer. This chapter provides the student with an overview of the major hardware components that make up a PLC system. In addition, students will receive an introduction into the input and output (I/O) section of a PLC and the common terms used to describe the various types of inputs and outputs. Chapter Objectives The following objectives are addressed in this chapter: 1. Describe several advantages of a programmable logic controller (PLC) over hardwired relay systems. 2. Identify the four major components of a typical PLC. 3. Describe the function of the four major components of a typical PLC. 4. Define the acronyms PLC, CPU, PC, I/O, ADC, and DAC. 5. Define the term discrete. 6. Define the term analog. What’s New in This Chapter The following elements are improvements in this chapter from the previous edition:  Updated with all new color figures and images  Updated with latest PLC hardware