1. Three Special Structures – Case, Do While, and Do Until
Many languages allow three additional structures:
case structure
do-while structure
do-until structure
Case Structure:
Decisions with more than two alternatives
Tests a variable against a series of values and takes action based on a match
Nested if-then-else statements will do what a case structure does
Programming Logic and Design, Introductory, Fourth Edition

2. Three Special Structures – Case, Do While, and Do Until (continued)
Using nested if-then-else for multiple alternatives
Programming Logic and Design, Introductory, Fourth Edition

3. Three Special Structures – Case, Do While, and Do Until (continued)
Using a case structure for multiple alternatives
Programming Logic and Design, Introductory, Fourth Edition

4. Three Special Structures – Case, Do While, and Do Until (continued)
do-while and do-until loops
Question is asked at the end of the loop structure
Ensures that the loop statements are always used at least once
Programming Logic and Design, Introductory, Fourth Edition

5. Three Special Structures – Case, Do While, and Do Until (continued)
do-while loop executes as long as the question’s answer is Yes or True Test checked at beginning May not be executed
do-until loop executes as long as the question’s answer is No or False (until it becomes Yes or True) Test checked at end of loop Will always execute loop at least once
Programming Logic and Design, Introductory, Fourth Edition

6. Three Special Structures – Case, Do While, and Do Until (continued)
while loop with question at beginning is called a pretest loop
do-until with question at end are called posttest loops
Programming Logic and Design, Introductory, Fourth Edition

7. Three Special Structures – Case, Do While, and Do Until (continued)
Programming Logic and Design, Introductory, Fourth Edition

8. Three Special Structures – Case, Do While, and Do Until (continued)
Programming Logic and Design, Introductory, Fourth Edition