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PLCs for Beginners

You're reading from   PLCs for Beginners An introductory guide to building robust PLC programs with structured text

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Product type Paperback
Published in May 2024
Publisher Packt
ISBN-13 9781803230931
Length 380 pages
Edition 1st Edition
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Author (1):
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M. T. White M. T. White
Author Profile Icon M. T. White
M. T. White
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Toc

Table of Contents (25) Chapters Close

Preface 1. Part 1: Basics of Computer Science for PLC Programmers FREE CHAPTER
2. Chapter 1: Computer Science Versus Automation Programming 3. Chapter 2: PLC Components – Integrating PLCs with Other Modules 4. Chapter 3: The Basics of Programming 5. Chapter 4: Unleashing Computer Memory 6. Chapter 5: Designing Programs – Unleashing Pseudocode and Flowcharts 7. Chapter 6: Boolean Algebra 8. Part 2: Introduction to Structured Text Programming
9. Chapter 7: Unlocking the Power of ST 10. Chapter 8: Exploring Variables and Tags 11. Chapter 9: Performing Calculations in Structured Text 12. Chapter 10: Unleashing Built-In Function Blocks 13. Chapter 11: Unlocking the Power of Flow Control 14. Chapter 12: Unlocking Advanced Control Statements 15. Chapter 13: Implementing Tight Loops 16. Part 3: Algorithms, AI, Security, and More
17. Chapter 14: Sorting with Loops 18. Chapter 15: Secure PLC Programming – Stopping Cyberthreats 19. Chapter 16: Troubleshooting PLCs – Fixing Issues 20. Chapter 17: Leveraging Artificial Intelligence (AI) 21. Chapter 18: The Final Project – Programming a Simulated Robot 22. Assessments 23. Index 24. Other Books You May Enjoy

Nested control statements

In the last chapter, we briefly looked at nested control statements. We had a CASE conditional with an IF statement inside it. When one control statement is nested inside another, they are typically referred to as either nested or embedded IF or CASE statements. A simple example of a nested IF statement is the beer and money analogy from before. Consider the following pseudocode:

Input age
Input money
If age >= 21 then
     If money >= 45 then
          Let them drink

For this example, two conditions must be true. First, the age of the person must be at least 21 years old. If so, they can move to the next conditional, which checks the amount of money they have. If they have at least $45, they can drink the beer. If any one of these conditionals is false, nothing will happen. In other words, they will not be able to drink! An easy way to think of these conditionals is as gatekeepers...

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