Lesson 8 more on repitition structure

© 2016 Cengage Learning®. May not be scanned, copied or
Introduction to Programming in C++
Eighth Edition
Lesson 8:
More on the Repetition Structure
duplicated, or posted to a publicly accessible website, in
whole or in part.

• Include aposttest loop in pseudocode
• Include aposttest loop in aflowchart
• Codeaposttest loop using the C++do while
statement
• Nest repetition structures
whole or in part.
An Introduction to Programming with C++, Eighth Edition 2
Objectives

• Repetition structures can be either pretest orposttest
loops
• Pretest loop – condition evaluated before instructions
are processed
• Posttest loop – condition evaluated afterinstructions
are processed
• Posttest loop’s instructions are always processedat
least once
• Pretest loop’s instructions may never beprocessed
whole or in part.
Posttest Loops

Figure 8-1 Problem specification, illustrations, and solutions
containing pretest and posttest loops
Posttest Loops (cont’d.)
whole or in part.

Posttest Loops (cont’d.)
Figure 8-2 Selection structure added to Solution 2 from Figure 8-1
whole or in part.

• Decision symbol in aflowchart (a diamond)
representing arepetition structure contains the loop
condition
• Decision symbol appears at the top ofapretest loop,
but at the bottom of aposttest loop
whole or in part.
Flowcharting a Posttest Loop

Figure 8-3 Commission Program’s problem specification and flowcharts
(cont’d.)
whole or in part.

Figure 8-3 Commission Program’s problem specification and flowchart
(cont’d.)
whole or in part.

• do whilestatement is used to code posttest loops in
C++
• Syntax:
do {
one or more statements to be processed one time,
and thereafter as long as the condition is true
} while (condition);
• Someprogrammers useacomment (such as:
//begin loop) to mark beginning ofloop
whole or in part.
The do while Statement

• Programmer must provide loop condition
– Must evaluate to aBooleanvalue
– May contain variables, constants, functions, arithmetic
operators, comparison operators, and logicaloperators
• Programmer must also provide statements to be
executed when condition evaluates to true
• Bracesare required around statements if thereare
more than one
whole or in part.
The do while Statement (cont’d.)

Figure 8-4 How to use the do while statement
whole or in part.

Figure 8-5 Commission Program containing a posttest loop
whole or in part.

• Like selection structures, repetition structures canbe
nested
• Youcan place one loop (the inner, or nestedloop)
inside another loop (the outerloop)
• Both loops can be pretest loops or posttest loops,or
the two loops may be differenttypes
• Programmer decides whether aproblem requires a
nested loop by analyzing the problemspecification
whole or in part.
Nested Repetition Structures

(cont’d.)
Figure 8-6 Problem specification and solution that requires a loop
whole or in part.

(cont’d.)
Figure 8-7 Modified problem specification and solution that
requires a nested loop
whole or in part.

• Simple program that simulates aclock with minutesand
seconds.
• Theouter loop representsminutes.
• Theinner loop (nested loop) representsseconds.
• To make it easier to desk-check the instructions, the nested
loop uses only three seconds per minute and the outer loop
stops after two minutes.
whole or in part.
The Clock Program

The Clock Program (cont’d.)
Figure 8-8 Algorithm, code, and a sample run of the Clock Program
whole or in part.

The Clock Program (cont’d.)
Figure 8-10 Completed desk-check table and output
whole or in part.

• Calculate the depreciation of acar overtime.
• Program usesacounter-controlled loop to display the
value of a new car at the end of each of five years, using
a15%annual depreciation rate.
whole or in part.
The Car Depreciation Program

Car Depreciation Program (cont’d.)
Figure 8-11 Beginning of Car Depreciation Program with Problem
Specification
whole or in part.

Figure 8-11 Remainder of Car Depreciation Program with sample
run
whole or in part.

• Modify the CarDepreciation Program to usedifferent
depreciation rates.
• Thismodified program displays the value of anewcar
at the end of each of five years, using annual
depreciation rates of 15%,20%,and25%.
whole or in part.

Figure 8-12 Beginning of the modified Car Depreciation Program
with problem specification
whole or in part.

Figure 8-12 Remainder of the modified Car Depreciation Program
with sample run
whole or in part.
24An Introduction to Programming with C++, Eighth Edition

Figure 8-13 Flowchart for the modified Car Depreciation Program
whole or in part.

• Arepetition structure can be either apretest loop ora
posttest loop
• In apretest loop, the loop condition is evaluatedbefore
the instructions in the loop are processed
• In aposttest loop, the evaluation occurs afterthe
instructions within the loop areprocessed
• Usethe do whilestatement to code aposttest loop
in C++
• Useeither the while statement or the for statement
to code apretest loop inC++
whole or in part.
Summary

• Repetition structures can be nested, which meansone
loop (called the inner or nested loop) can be placed
inside another loop (called the outerloop)
• For nested repetition structures towork correctly, the
entire inner loop must be contained within the outer
loop
whole or in part.
Summary (cont’d.)

Lesson 8 more on repitition structure

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