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Starting Out with C++, 3rdEdition
1
The Increment and Decrement Operators
++ and -- are operators that add and subtract
one from their operands.
num = num + 1;
num += 1;
num++;
Starting Out with C++, 3rdEdition
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Program 5-1// This program demonstrates the increment and decrement
// operators.
#include
void main(void)
{
int bigVal = 10, smallVal = 1;
cout
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Starting Out with C++, 3rdEdition
5
Program 5-2
//This program demonstrates the prefix and postfix modes of the
// increment and decrement operators.
#include
void main(void)
{
int bigVal = 10, smallVal = 1;
cout
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Starting Out with C++, 3rdEdition
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5.2 Introduction to Loops - The while
Loop
A loop is part of a program that repeats.
A while loop is a pre test loop - the
expression is tested before the loop is
executed
while (expression)
statement;
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Program 5-3// This program demonstrates a simple while loop.
#include
void main(void)
{
int number = 0;
cout number;}
Starting Out with C++, 3rdEdition
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Program Output with Example Input
This program will let you enter number after number. Enter
99 when you want to quit the program.
1 [Enter]
2 [Enter]
30 [Enter]
75 [Enter]
99 [Enter]
Starting Out with C++, 3rdEdition
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Terminating a Loop
A loop that does not have a way of stopping is called
an infinite loop
int test = 0;
while (test < 10)
cout
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Starting Out with C++, 3rdEdition
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Programming Style and the while Loop
If there is only one statement repeated by
the loop, it should appear on the line after
the while statement and be indented one
additional level
If the loop repeats a block, the block shouldbegin on the line after the while statement
and each line inside the braces should beindented
Starting Out with C++, 3rdEdition
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5.3 Counters
A counter is a variable that is incremented
or decremented each time a loop iterates.
Starting Out with C++, 3rdEdition
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Program 5-4
// This program displays the numbers 1 through 10 and
// their squares.
#include
void main(void)
{
int num = 1; // Initialize counter
cout
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Starting Out with C++, 3rdEdition
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Program 5-5
// This program displays the numbers 1 through 10
and
// their squares.
#include
void main(void)
{
int num = 0;
cout
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Starting Out with C++, 3rdEdition
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Program continued from previous slide.
while (count++ < numStudents)
{
int score1, score2, score3;
float average;
cout > score2 >> score3;
average = (score1 + score2 + score3) / 3.0;
cout
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Starting Out with C++, 3rdEdition
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Program continues
while (count++ < days)
{
float sales;
cout
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Starting Out with C++, 3rdEdition
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Program continued from previous slide.
while (points != -1)
{
count++;
cout > score3;
average = (score1 + score2 + score3) / 3.0;
cout
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Starting Out with C++, 3rdEdition
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Program Output w ith Example Input
Enter 3 scores and I will average them: 80 90 70 [Enter]
The average is 80.
Do you want to average another set? (Y/N) y [Enter]
Enter 3 scores and I will average them: 60 75 88 [Enter]
The average is 74.333336.
Do you want to average another set? (Y/N) n [Enter]
Starting Out with C++, 3rdEdition
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The for Loop
Ideal for situations that require a counter
because it has built-in expressions that
initialize and update variables.
for (initialization; test; update)
statement;
Starting Out with C++, 3rdEdition
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Program 5-11// This program displays the numbers 1 through 10 and
// their squares.
#include
void main(void)
{
int num;
cout
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Starting Out with C++, 3rdEdition
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Omitting the for Loops Expressions
int num = 1;
for ( ; num
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Starting Out with C++, 3rdEdition
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Program Output with Example Input
Enter the sales for day 1: 489.32 [Enter]
Enter the sales for day 2: 421.65 [Enter]
Enter the sales for day 3: 497.89 [Enter]
Enter the sales for day 4: 532.37 [Enter]
Enter the sales for day 5: 506.92 [Enter]
Enter the sales for day 6: 489.01 [Enter]
Enter the sales for day 7: 476.55 [Enter]
The total sales are $3413.71
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5.8 Other forms of the update
expression
Incrementing the counter by something besides 1:for(number = 2; number
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Starting Out with C++, 3rdEdition
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Program 5-13
// This program averages test scores. It asks the user for the
// number of students and the number of test scores per student.
#include
void main(void)
{
int numStudents, numTests, total;
float average;
cout numStudents;
cout > numTests;
Program continues
Starting Out with C++, 3rdEdition
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Program continued from previous slide.
for (int count1 = 1; count1
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Starting Out with C++, 3rdEdition
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Program 5-14// This program raises the user's number to the powers
// of 0 through 10.
#include
#include
void main(void)
{
int value;
char choice;
cout > value;
cout