An Introduction to Programming with C++ Fifth Edition Chapter 8 More on the Repetition Structure

An Introduction to Programming with C++

Fifth Edition

Chapter 8More on the Repetition Structure

An Introduction to Programming with C++, Fifth Edition 2

Objectives

• Include the posttest repetition structure in pseudocode

• Include the posttest repetition structure in a flowchart

• Code a posttest loop using the C++ do while statement

• Nest repetition structures

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Concept Lesson

• Posttest Loops

• Coding the Posttest Loop

• Nested Repetition Structures

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Posttest Loops

• Loops can be pretest or posttest

• Condition in a posttest loop is evaluated with each loop iteration– Evaluation occurs after instructions within loop are

processed• Also called bottom-driven loops

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Posttest Loops (continued)

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Flowcharting a Posttest Loop

• Flowcharts illustrate why loops are referred to as pretest and posttest loops– Repetition diamond appears at the top of a pretest

loop, but at the bottom of a posttest loop

Flowcharting a Posttest Loop (continued)

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An Introduction to Programming with C++, Fifth Edition 8

Flowcharting a Posttest Loop (continued)

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Flowcharting a Posttest Loop (continued)

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Coding the Posttest Loop

• Use the while statement or the for statement to code a pretest loop in C++

• Use the do while statement to code a posttest loop in C++– The loop condition must be a Boolean expression

• Can contain variables, constants, functions, and arithmetic/comparison/logical operators

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Coding the Posttest Loop (continued)

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Posttest Loop Example – O’Donnell Incorporated Program

• Problem description– In January of each year, O’Donnell Incorporated

pays a 10% bonus to each of its salespeople– Bonus based on amount of sales made by

salesperson during previous year– Payroll clerk wants a program that calculates and

displays each salesperson’s bonus amount

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Posttest Loop Example – O’Donnell Incorporated Program (continued)

An Introduction to Programming with C++, Fifth Edition 14

Posttest Loop Example – O’Donnell Incorporated Program

(continued)

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Nested Repetition Structures

• In a nested repetition structure, one loop (inner loop) is placed entirely within another loop (outer loop)

Nested Repetition Structures (continued)

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An Introduction to Programming with C++, Fifth Edition 17

Nested Loop Example – Max Beauty Supply Program

• Max Beauty Supply divides its sales territory into two regions: Region 1 and Region 2

• Sales manager wants a program to enter the sales amounts for both regions, one region at a time– Program should calculate the total amount sold in

the current region, and display that information

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Nested Loop Example – Max Beauty Supply Program (continued)

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Nested Loop Example – Max Beauty Supply Program (continued)

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Nested Loop Example – Max Beauty Supply Program (continued)

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Nested Loop Example – Max Beauty Supply Program (continued)

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Summary

• A repetition structure can be a pretest or posttest loop– In a pretest loop, the loop condition is evaluated before

the instructions in the loop body are processed• Instructions may never be processed

• Use while or for statements

– In a posttest loop, the loop condition is evaluated after the instructions in the loop body are processed

• Instructions are always processed at least once

• Use the do while statement

• You can nest repetition structures

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Application Lesson: Using a Nested Repetition Structure in a C++ Program• Lab 8.1: Stop and Analyze

• Lab 8.2– Create a program that displays one or more

multiplication tables for Mrs. Johnson students

• Lab 8.3– Modify program so it uses a posttest loop (instead of

a pretest loop) to display the multiplication tables

• Lab 8.4: Desk-Check Lab

• Lab 8.5: Debugging Lab