1. Chapter 5: The Selection Structure
Introduction to Programming with C++
Fourth Edition

2. Objectives Use the selection structure in a program
Write pseudocode for the selection structure
Create a flowchart for the selection structure
Code the if and if/else forms of the selection structure
Introduction to Programming with C++, Fourth Edition

3. Objectives (continued)
Write code that uses comparison operators and logical operators
Convert the contents of a char variable to uppercase or lowercase
Convert the contents of a string variable to uppercase or lowercase
Introduction to Programming with C++, Fourth Edition

4. Using the Selection Structure
Selection structure/decision structure – allows the program to make a decision or comparison and then select one of two paths, depending on the result of the comparison
Condition
Specifies the decision you are making
Must result in either a true or false answer
Introduction to Programming with C++, Fourth Edition

5. Selection Structures You Might Use Today
Introduction to Programming with C++, Fourth Edition

6. Including the Selection Structure in Pseudocode
True path - instructions following the condition
False path
When using else, false path includes instructions between else and end if
When else is not used, processing continues after the end if
Introduction to Programming with C++, Fourth Edition

7. Including the Selection Structure in Pseudocode (continued)
Introduction to Programming with C++, Fourth Edition

8. Drawing a Flowchart of a Selection Structure
Flowcharts - use standardized symbols to show steps the computer must take to accomplish the program’s goal
Diamond symbol (selection/repetition symbol) – used to represent both selection and repetition
Introduction to Programming with C++, Fourth Edition

9. Drawing a Flowchart of a Selection Structure (continued)
Introduction to Programming with C++, Fourth Edition

10. Coding the Selection Structure
Items in square brackets ([ ]) in the syntax are optional
You create a statement block by enclosing the statements in a set of braces ({ })
Although not required, it is a good programming practice to use a comment, such as //end if, to mark the end of each if statement
Introduction to Programming with C++, Fourth Edition

11. Syntax of the C++ if statement
Introduction to Programming with C++, Fourth Edition

12. Coding the Selection Structure
Introduction to Programming with C++, Fourth Edition

13. Comparison Operators
Comparison (relational) operators - to make comparisons in a C++ program
Precedence numbers - indicate the order in which the computer performs the comparisons in a C++ expression
Parentheses - override the order of precedence
Introduction to Programming with C++, Fourth Edition

14. Comparison Operators (continued)
Introduction to Programming with C++, Fourth Edition

15. Comparison Operators (continued)
Introduction to Programming with C++, Fourth Edition

16. Comparison Operators (continued)
Introduction to Programming with C++, Fourth Edition

17. Comparison Operators (continued)
Introduction to Programming with C++, Fourth Edition

18. Swapping Values Four instructions that swap the two values:
int temp = 0; creates and initializes a local variable named temp
temp = first; assigns the value contained in the first variable to the temp variable
first = second; assigns the value contained in the second variable to the first variable
second = temp; assigns the value contained in the temp variable to the second variable
Introduction to Programming with C++, Fourth Edition

19. Illustration of the Swapping Concept
Introduction to Programming with C++, Fourth Edition

20. Logical Operators Logical/Boolean operators - And and Or
Allow you to combine two or more conditions into one compound condition
And logical operator - all of the conditions must be true for the compound condition to be true
Or logical operator - only one of the conditions must be true for the compound condition to be true
Introduction to Programming with C++, Fourth Edition

21. Truth Tables for the And and Or Logical Operators
Introduction to Programming with C++, Fourth Edition

22. Logical Operators
Introduction to Programming with C++, Fourth Edition

23. Logical Operators (continued)
Introduction to Programming with C++, Fourth Edition

24. Using Logical Operators in a Program
Data validation - the process of verifying that the input data is within the expected range
Introduction to Programming with C++, Fourth Edition

25. Comparing Characters Character comparisons are case-sensitive
‘Y’ is not the same as the character ‘y’
toupper(charVariable) function - converts a character to uppercase
tolower(charVariable) function - converts a character to lowercase
Introduction to Programming with C++, Fourth Edition

26. Comparing Strings String comparisons are case-sensitive
“YES” is not the same as the string “yes”
transform() - converts a string
Syntax
transform(str.begin(), str.end(), str2.begin, function);
For example, if name is a string, the following converts it to lowercase:
transform(name.begin(), name.end(), name.begin, tolower);
Introduction to Programming with C++, Fourth Edition

27. Summary
Selection structure allows the program to make a decision or comparison and then select one of two paths, depending on the result of the comparison
Use comparison and logical operators
Operations on chars include:
Changing case (toupper and tolower)
Operations on strings include:
transform function
Introduction to Programming with C++, Fourth Edition