Starting Out with C++, 3 rd Edition 1 Chapter 14 – More About Classes.
Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.
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Transcript of Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.
![Page 1: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/1.jpg)
1
Starting Out with C++, 3rd Edition
Chapter 4. Making Decisions
![Page 2: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/2.jpg)
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Starting Out with C++, 3rd Edition
4.1 Relational Operators
• Relational operators allow you to compare numeric values and determine if one is greater than, less than, equal to, or not equal to another.
![Page 3: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/3.jpg)
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Starting Out with C++, 3rd Edition
Table 4-1
Relational Operators(in Order of Precedence)
Meaning
><> =< == =!=
Greater thanLess thanGreater than or equaltoLess than or equal toEqual toNot equal to
![Page 4: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/4.jpg)
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Starting Out with C++, 3rd Edition
Table 4-2
Expression What the Expression Means
X > YX < YX > = YX < = YX = = YX != Y
Is X greater than Y ?Is X less than Y ?Is X greater than or equal to Y ?Is X less than or equal to Y ?Is X equal to Y ?Is X not equal to Y ?
![Page 5: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/5.jpg)
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Starting Out with C++, 3rd Edition
The Value of a Relationship
• Relational expressions are also know as a Boolean expression
• Warning! The equality operator is two equal signs together
==
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Starting Out with C++, 3rd Edition
Table 4-3
Expression Value
X < Y False, because X is not less than Y .
X > Y True, because X is greater than Y .
X > = Y True, because X is greater than or equal to Y .
X < = Y False, because X is not less than or equal to Y .
Y != X True, because Y is not equal to X .
![Page 7: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/7.jpg)
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Starting Out with C++, 3rd Edition
Program 4-1// This program displays the values of true and false
// states.
#include <iostream.h>
void main(void)
{int trueValue, falseValue, x = 5, y = 10;
trueValue = X < Y;falseValue = Y == X;
cout << "True is " << trueValue << endl;cout << "False is " << falseValue << endl;
}Program OutputTrue is 1False is 0
![Page 8: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/8.jpg)
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Starting Out with C++, 3rd Edition
Table 4-4 (Assume x is 10, y is 7, a and b are ints)
Statement Outcome
Z = X < Y Z is assigned 0 because X is not less than Y .
c o u t < < (X > Y ); Displays 1 because X is greater than Y .
A = X > = Y ; A is assigned 1 because X is greater than orequal to Y .
c o u t < < (X < =Y );
Displays 0 because X is not less than orequal to Y .
B = Y != X ; B is assigned 1 because Y is not equal to X .
![Page 9: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/9.jpg)
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Starting Out with C++, 3rd Edition
4.2 The if Statement
• The if statement can cause other statements to execute only under certain conditions.
![Page 10: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/10.jpg)
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Starting Out with C++, 3rd Edition
Program 4-2// This program averages 3 test scores#include <iostream.h>
void main(void){
int score1, score2, score3;float average;
cout << "Enter 3 test scores and I will average them: ";cin >> score1 >> score2 >> score3;average = (score1 + score2 + score3) / 3.0;cout.precision(1);cout.setf(ios::showpoint | ios::fixed);cout << "Your average is " << average << endl;if (average > 95)
cout << "Congratulations! That's a high score!\n";
}
![Page 11: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/11.jpg)
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter 3 test scores and I will average them: 80 90 70 [Enter]Your average is 80.0
Program Output with Other Example InputEnter 3 test scores and I will average them: 100 100 100 [Enter]Your average is 100.0
Congratulations! That's a high score!
![Page 12: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/12.jpg)
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Starting Out with C++, 3rd Edition
Table 4-5
Statements Outcome
if (H o u rs > 4 0 ) O v e rT im e = 1 ;
Assigns 1 to O v erT im e only when H o u rs is greater than 40
if (V a lu e > 3 2 ) co u t < < " In v a lid n u m b er \n " ;
Displays the message “Invalid number” only when V a lu e is greater than 32
if (O v e rT im e = = 1 ) P ay R a te * = 2 ;
Multiplies P ay R a te by 2 only when O v erT im e is equal to 1
![Page 13: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/13.jpg)
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Starting Out with C++, 3rd Edition
Be Careful With Semicolons
if (expression)
statement;• Notice that the semicolon comes after the
statement that gets executed if the expression is true; the semicolon does NOT follow the expression
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Starting Out with C++, 3rd Edition
Program 4-3// This program demonstrates how a misplaced semicolon// prematurely terminates an if statement.#include <iostream.h>
void main(void){
int x = 0, y = 10;cout << “x is " << x << " and y is " << y << endl;if (x > y); // misplaced semicolon!
cout << “x is greater than y\n"; // Always executed
}
Program OutputX is 0 and Y is 10
X is greater than Y
![Page 15: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/15.jpg)
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Starting Out with C++, 3rd Edition
Programming Style and the if Statement
• The conditionally executed statement should appear on the line after the if statement.
• The conditionally executed statement should be indented one “level” from the if statement.
• Note: Each time you press the tab key, you are indenting one level.
![Page 16: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/16.jpg)
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Starting Out with C++, 3rd Edition
Comparing Floating Point Numbers
• Round-off errors can cause problems when comparing floating point numbers with the equality operator (==)
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Starting Out with C++, 3rd Edition
Program 4-4// This program demonstrates how floating point round-off// errors can make equality comparisons unreliable. #include <iostream.h> void main(void){float result;
result = 6.0 * 0.666666; // Round-off errorif (result == 4.0)cout << "It's true!";
elsecout << "It's false!";
}
Program OutputIt's false!
![Page 18: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/18.jpg)
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Starting Out with C++, 3rd Edition
And Now Back to Truth
• When a relational expression is true, it has the value 1.
• When a relational expression is false it has the value 0.
• An expression that has the value 0 is considered false by the if statement.
• An expression that has any value other than 0 is considered true by the if statement.
![Page 19: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/19.jpg)
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Starting Out with C++, 3rd Edition
Not All Operators Are “Equal”
• Consider the following statement:if (x = 2) // caution here!
cout << “It is True!”;
• This statement does not determine if x is equal to 2, it assigns x the value 2, therefore, this expression will always be true because the value of the expression is 2, a non-zero value
![Page 20: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/20.jpg)
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Starting Out with C++, 3rd Edition
Program 4-5// This program averages 3 test scores. The if statement uses// the = operator, but the == operator was intended.#include <iostream.h>
void main(void){
int score1, score2, score3;float average;
cout << "Enter 3 test scores and I will average them: ";cin >> score1 >> score2 >> score3;average = (score1 + score2 + score3) / 3.0;cout.precision(1);cout.setf(ios::showpoint | ios::fixed);cout << "Your average is " << average << endl;if (average = 100) // Wrong
cout << "Congratulations! That's a high score!\n";
}
![Page 21: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/21.jpg)
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Starting Out with C++, 3rd Edition
Program 4-5 Output With Example Input
Program Output with Example InputEnter your 3 test scores and I will average them: 80 90 70[Enter]Your average is 80.0Congratulations! That’s a perfect score!
![Page 22: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/22.jpg)
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Starting Out with C++, 3rd Edition
4.3 Flags
• A flag is a variable, usually a boolean or an integer, that signals when a condition exists.
• If your compiler does not support the bool data type, use int instead.
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Starting Out with C++, 3rd Edition
Program 4-6// This program averages 3 test scores. It uses the variable highScore as a flag.#include <iostream.h>
void main(void){
int score1, score2, score3;float average;bool highScore = false;
cout << "Enter your 3 test scores and I will average them: ";cin >> score1 >> score2 >> score3;average = (score1 + score2 + score3) / 3.0;if (average > 95)
highScore = true; // Set the flag variablecout.precision(1);cout.setf(ios::showpoint | ios::fixed);cout << "Your average is " << average << endl;if (highScore)
cout << "Congratulations! That's a high score!\n";\} Program Output with Example InputEnter your 3 test scores and I will average them: 100 100 100 [Enter]Your average is 100.0Congratulations! That's a high score!
![Page 24: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/24.jpg)
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Starting Out with C++, 3rd Edition
4.4 Expanding the if Statement
• The if statement can conditionally execute a block of statement enclosed in braces.
if (expression)
{
statement;
statement;
// Place as many statements here as necessary.
}
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Starting Out with C++, 3rd Edition
Program 4-7// This program averages 3 test scores.// It uses the variable highScore as a flag.#include <iostream.h>
void main(void){
int score1, score2, score3;float average;bool highScore = false;cout << "Enter 3 test scores and I will average them: ";cin >> score1 >> score2 >> score3;average = (score1 + score2 + score3) / 3.0;if (average > 95)
highScore = true; // Set the flag variable
Program continues on next slide…
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Starting Out with C++, 3rd Edition
Program continued from previous slide
cout.precision(1);cout.setf(ios::showpoint | ios::fixed);cout << "Your average is " << average << endl;if (highScore){
cout << "Congratulations!\n";cout << "That's a high score.\n";cout << "You deserve a pat on the back!\
n";}
}
![Page 27: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/27.jpg)
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter your 3 test scores and I will average them: 100 100 100 [Enter]
Your average is 100.0Congratulations!That's a high score.
You deserve a pat on the back!
Program Output with Different Example Input
Enter your 3 test scores and I will average them: 80 90 70 [Enter]
Your average is 80.0
![Page 28: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/28.jpg)
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Starting Out with C++, 3rd Edition
Don’t Forget the Braces!
• If you intend to execute a block of statements with an if statement, don’t forget the braces.
• Without the braces, the if statement only executes the very next statement.
![Page 29: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/29.jpg)
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Starting Out with C++, 3rd Edition
Program 4-8// This program averages 3 test scores.// It uses the variable highScore as a flag.#include <iostream.h>
void main(void){
int score1, score2, score3;float average;bool highScore = false;
cout << "Enter 3 test scores and I will average them: ";cin >> score1 >> score2 >> score3;average = (score1 + score2 + score3) / 3.0;if (average > 95)
highScore = true; // Set the flag variable
Program continues on next slide…
![Page 30: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/30.jpg)
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Starting Out with C++, 3rd Edition
Program continued from previous slide
cout.precision(1);cout.setf(ios::showpoint | ios::fixed);cout << "Your average is " << average << endl;
// The following if statement is // missing its braces!
if (highScore)cout << "Congratulations!\n";cout << "That's a high score.\n";cout << "You deserve a pat on the back!\
n";
}
![Page 31: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/31.jpg)
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter your 3 test scores and I will average them: 100 100 100[Enter]Your average is 100Congratulations!That’s a high score.You deserve a pat on the back!
Program Output with Different Example Input
Enter your 3 test scores and I will average them: 80 90 70[Enter]Your average is 100Congratulations!That’s a high score.You deserve a pat on the back!
![Page 32: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/32.jpg)
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Starting Out with C++, 3rd Edition
4.5 The if/else Statement
• The if/else statement will execute one group of statements if the expression is true, or another group of statements if the expression is false.
if (expression)
statement or block of statements;
else
statement or block of statements;
![Page 33: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/33.jpg)
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Starting Out with C++, 3rd Edition
Program 4-9
// This program uses the modulus operator to determine// if a number is odd or even. If the number is evenly divided// by 2, it is an even number. A remainder indicates it is odd.#include <iostream.h>
void main(void){
int number;cout << "Enter an integer and I will tell you if it\n";cout << "is odd or even. ";cin >> number;if (number % 2 == 0)
cout << number << " is even.\n";else
cout << number << " is odd.\n";
}
![Page 34: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/34.jpg)
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter an integer and I will tell you if itis odd or even. 17 [Enter]17 is odd.
![Page 35: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/35.jpg)
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Starting Out with C++, 3rd Edition
Program 4-10// This program asks the user for two numbers, num1 and num2.// num1 is divided by num2 and the result is displayed.// Before the division operation, however, num2 is tested// for the value 0. If it contains 0, the division does not// take place.#include <iostream.h>
void main(void){
float num1, num2, quotient;
cout << "Enter a number: ";cin >> num1;cout << "Enter another number: ";cin >> num2;
Program continues on next slide…
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Starting Out with C++, 3rd Edition
Program continued from previous slide.
if (num2 == 0){
cout << "Division by zero is not possible.\n";cout << "Please run the program again and enter\n";cout << "a number besides zero.\n";
}else{
quotient = num1 / num2;cout << "The quotient of " << num1 << " divided by ";cout << num2 << " is " << quotient << ".\n";
}
}
![Page 37: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/37.jpg)
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Starting Out with C++, 3rd Edition
Program Output
(When the user enters 0 for num2)Enter a number: 10 [Enter]Enter another number: 0 [Enter]Division by zero is not possible.Please run the program again and enter
a number besides zero.
![Page 38: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/38.jpg)
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Starting Out with C++, 3rd Edition
4.6 The if/else if Construct
The if/else if statement is a chain of if statements. The perform their tests, one after the other, until one of them is found to be true.
If (expression)
statement or block of statements;
else if (expression)
statement or block of statements;
// put as many else it’s as needed here
else if (expression)
statement or block of statements;
![Page 39: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/39.jpg)
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Starting Out with C++, 3rd Edition
Program 4-11// This program uses an if/else if statement to assign a// letter grade (A, B, C, D, or F) to a numeric test score.#include <iostream.h>
void main(void){
int testScore;char grade;
cout << "Enter your numeric test score and I will\n";cout << "tell you the letter grade you earned: ";cin >> testScore;
Program continues on next slide…
![Page 40: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/40.jpg)
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Starting Out with C++, 3rd Edition
if (testScore < 60)grade = 'F';
else if (testScore < 70)grade = 'D';
else if (testScore < 80)grade = 'C';
else if (testScore < 90)grade = 'B';
else if (testScore <= 100)grade = 'A';
cout << "Your grade is " << grade << ".\n";
}
Program continued from previous slide.
![Page 41: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/41.jpg)
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter your test score and I willtell you the letter grade you earned: 88 [Enter]Your grade is B.
![Page 42: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/42.jpg)
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Starting Out with C++, 3rd Edition
Program 4-12// This program uses independent if/else statements to assign a// letter grade (A, B, C, D, or F) to a numeric test score.// Do you think it will work?#include <iostream.h>
void main(void){
int testScore;char grade;
cout << "Enter your test score and I will tell you\n";cout << "the letter grade you earned: ";cin >> testScore;
Program continues on next slide…
![Page 43: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/43.jpg)
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Starting Out with C++, 3rd Edition
if (testScore < 60)grade = 'F';
if (testScore < 70)grade = 'D';
if (testScore < 80)grade = 'C';
if (testScore < 90)grade = 'B';
if (testScore <= 100)grade = 'A';
cout << "Your grade is " << grade << ".\n";
}
Program continued from previous slide.
![Page 44: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/44.jpg)
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter your test score and I will tell youthe letter grade you earned: 40 [Enter]Your grade is A.
![Page 45: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/45.jpg)
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Starting Out with C++, 3rd Edition
Program 4-13//This program uses an if/else if statement to//assign a letter grade ( A, B, C, D, or F )//to a numeric test score.#include<iostream.h>
void main(void){
int testScore;cout << "Enter your test score and I will tell you\n";cout << "the letter grade you earned: ";cin >> testScore;if (testScore < 60){
cout << "Your grade is F.\n"; cout << "This is a failing grade. Better see your "; cout << "instructor.\n"; } else if (testScore < 70) { cout << "Your grade is D.\n"; cout << "This is below average. You should get "; cout << "tutoring.\n"; }
Program continues on next slide…
![Page 46: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/46.jpg)
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Starting Out with C++, 3rd Edition
else if (testScore < 80) { cout << "Your grade is C.\n"; cout << "This is average.\n"; } else if(testScore < 90) { cout << "Your grade is B.\n"; cout << "This is an above average grade.\n"; } else if (testScore <= 100) { cout << "Your grade is A.\n"; cout << "This is a superior grade. Good work!\n"; }}
Program continued from previous slide.
![Page 47: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/47.jpg)
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter your test score and I will tell youthe letter grade you earned: 94 [Enter]Your grade is A.
This is a superior grade. Good work!
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Starting Out with C++, 3rd Edition
4.7 Using a Trailing else
• A trailing else, placed at the end of an if/else if statement, provides default action when none of the if’s have true expressions
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Starting Out with C++, 3rd Edition
Program 4-14// This program uses an if/else if statement to assign a// letter grade (A, B, C, D, or F) to a numeric test score.// A trailing else has been added to catch test scores > 100.
#include <iostream.h>
void main(void){
int testScore;
cout << "Enter your test score and I will tell you\n";cout << "the letter grade you earned: ";cin >> testScore;
Program continues on next slide…
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Starting Out with C++, 3rd Edition
if (testScore < 60){
cout << "Your grade is F.\n";cout << "This is a failing grade. Better see your ";cout << "instructor.\n";
}else if (testScore < 70){
cout << "Your grade is D.\n";cout << "This is below average. You should get ";cout << "tutoring.\n";
}
Program continued from previous slide.
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Starting Out with C++, 3rd Edition
else if (testScore < 80){
cout << "Your grade is C.\n";cout << "This is average.\n";
}else if (testScore < 90){
cout << "Your grade is B.\n";cout << "This is an above average grade.\n";
}
Program continued from previous slide.
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Starting Out with C++, 3rd Edition
else if (testScore <= 100){
cout << "Your grade is A.\n";cout << "This is a superior grade. Good work!\n";
}else // Default action{
cout << testScore << " is an invalid score.\n";cout << "Please enter scores no greater than 100.\n";
}
}
Program continued from previous slide.
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter your test score and I will tell you
the letter grade you earned: 104 [Enter]104 is an invalid score.
Please enter scores no greater than 100.
![Page 54: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/54.jpg)
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Starting Out with C++, 3rd Edition
4.8 Focus on Software Engineering: Menus
• You can use the if/else if statement to create menu-driven programs. A menu-driven program allows the user to determine the course of action by selecting it from a list of actions.
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Starting Out with C++, 3rd Edition
Program 4-15// This program displays a menu and asks the user to make a// selection. An if/else if statement determines which item// the user has chosen.#include <iostream.h>
void main(void){
int choice, months;float charges;
cout << "\t\tHealth Club Membership Menu\n\n";cout << "1. Standard Adult Membership\n";cout << "2. Child Membership\n";cout << "3. Senior Citizen Membership\n";cout << "4. Quit the Program\n\n";
Program continues on next slide…
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Starting Out with C++, 3rd Edition
cout << "Enter your choice: ";cin >> choice;cout.setf(ios::fixed | ios::showpoint);cout.precision(2);if (choice == 1){
cout << "\nFor how many months? ";cin >> months;charges = months * 40.00;cout << "The total charges are $" << charges <<
endl;}
Program continued from previous slide.
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Starting Out with C++, 3rd Edition
else if (choice == 2){
cout << "\nFor how many months? ";cin >> months;charges = months * 20.00;cout << "The total charges are $" << charges << endl;
}else if (choice == 3){
cout << "\nFor how many months? ";cin >> months;charges = months * 30.00;cout << "The total charges are $" << charges << endl;
}
Program continued from previous slide.
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Starting Out with C++, 3rd Edition
else if (choice != 4){
cout << "The valid choices are 1 through 4. Run the\n";cout << "program again and select one of those.\n";
}
}
Program continued from previous slide.
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Health Club Membership Menu1. Standard Adult Membership2. Child Membership3. Senior Citizen Membership4. Quit the Program
Enter your choice: 3 [Enter]For how many months? 6 [Enter]The total charges are $180.00
![Page 60: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/60.jpg)
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Starting Out with C++, 3rd Edition
4.9 Focus on Software Engineering: Nested if Statements
• A nested if statement is an if statement in the conditionally-executed code of another if statement.
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Starting Out with C++, 3rd Edition
Program 4-16// This program demonstrates the nested if statement.#include <iostream.h>
void main(void){
char employed, recentGrad;cout << "Answer the following questions\n";cout << "with either Y for Yes or ";cout << "N for No.\n";cout << "Are you employed? ";cin >> employed;cout << "Have you graduated from college ";cout << "in the past two years? ";cin >> recentGrad;
Program continues on next slide…
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Starting Out with C++, 3rd Edition
if (employed == 'Y'){
if (recentGrad == 'Y') // Nested if{
cout << "You qualify for the special ";cout << "interest rate.\n";
}}
}
Program continued from previous slide.
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Answer the following questionswith either Y for Yes or N for No.Are you employed? Y[Enter]Have you graduated from college in the past two years? Y[Enter]You qualify for the special interest rate.
![Page 64: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/64.jpg)
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Starting Out with C++, 3rd Edition
Program Output with Other Example Input
Answer the following questionswith either Y for Yes or N for No.Are you employed? Y[Enter]Have you graduated from college in the past two years? N[Enter]
![Page 65: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/65.jpg)
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Starting Out with C++, 3rd Edition
4.10 Logical Operators
• Logical operators connect two or more relational expressions into one, or reverse the logic of an expression.
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Starting Out with C++, 3rd Edition
Table 4-6Operator Meaning Effect
& & AND Connects two expressions into one. Bothexpressions must be true for the overallexpression to be true.
|| OR Connects two expressions into one. One orboth expressions must be true for the overallexpression to be true. It is only necessary forone to be true, and it does not matter which.
! NOT The ! operator reverses the “truth” of anexpression. It makes a true expression false,and a false expression true.
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Table 4-7
Expression 1 Expression 2 Expression 1 &&Expression 2
TrueFalseFalseTrue
FalseTrueFalseTrue
False (0)False (0)False (0)True (1)
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Starting Out with C++, 3rd Edition
Program 4-18// This program demonstrates the && logical operator.#include <iostream.h>
void main(void){ char employed, recentGrad;
cout << "Answer the following questions\n"; cout << "with either Y for Yes or "; cout << "N for No.\n"; cout << "Are you employed? "; cin >> employed;
Program continues on next slide…
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cout << "Have you graduated from college "; cout << "in the past two years? "; cin >> recentGrad; if (employed == 'Y‘ && recentGrad == 'Y') // && Operator { cout << "You qualify for the special "; cout << "interest rate.\n"; } else { cout << "You must be employed and have \n"; cout << "graduated from college in the\n"; cout << "past two years to qualify.\n"; }
}
Program continued from previous slide.
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Answer the following questionswith either Y for Yes orN for No.Are you employed? Y[Enter]Have you graduated from college in the past two years? N[Enter]You must be employed and havegraduated from college in thepast two years to qualify.
![Page 71: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/71.jpg)
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Table 4-8
Expression 1 Expression 2 Expression 1 ||Expression 2
True False True (1)
False True True (1)
False False False (0)
True True True (1)
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Starting Out with C++, 3rd Edition
Program 4-19
// This program asks the user for their annual income and // the number of years they have been employed at their current// job. The || operator is used in a if statement that// determines if the income is at least $35,000 or their time// on the job is more than 5 years.
#include <iostream.h>
void main(void){
float income;int years;
Program continues on next slide…
![Page 73: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/73.jpg)
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Program continues
cout << "What is your annual income? ";cin >> income;cout << "How many years have you worked at " << "your current job? ";cin >> years;if (income >= 35000 || years > 5) // Use || logical operator
cout << "You qualify.\n";else{
cout << "You must earn at least $35,000 or have\n";cout << "been employed for more than 5 years.\n";
}
}
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Starting Out with C++, 3rd Edition
Program Output with Example Input
What is your annual income? 40000 [Enter]How many years have you worked at your current job? 2
[Enter]You qualify.
Program Output with Example InputWhat is your annual income? 20000 [Enter]How many years have you worked at your current job? 7
[Enter]You qualify.
![Page 75: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/75.jpg)
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Starting Out with C++, 3rd Edition
Table 4-9
Expression !(Expression)
True False (0)
False True (1)
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Starting Out with C++, 3rd Edition
Program 4-20//This program asks the user for his annual income and //the number of years he has been employed at his current job. //The ! operator reverses the logic of the expression in the if/else statement.#include <iostream.h>
void main(void){
float income; int years;cout << "What is your annual income? ";cin >> income;cout << "How many years have you worked at " << "your current job? ";cin >> years;if (!(income >= 35000 || years > 5)) // Uses the ! Logical operator{
cout << "You must earn at least $35,000 or have\n";cout << "been employed for more than 5 years.\n";
}else
cout << "You qualify.\n";
}
![Page 77: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/77.jpg)
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Starting Out with C++, 3rd Edition
Precedence of Logical Operators
!
&&
||
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Starting Out with C++, 3rd Edition
4.11 Checking Numeric Ranges With Logical Operators
• Logical operators are effective for determining if a number is in or out of a range.
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Starting Out with C++, 3rd Edition
4.12 Focus on Software Engineering: Validating User Input
• As long as the user of a program enters bad input, the program will produce bad output. Program should be written to filter out bad input.
![Page 80: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/80.jpg)
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Examples of validation:
• Numbers are check to ensure they are within a range of possible values.
• Values are check for their “reasonableness”.• Items selected from a menu or other set of choices
are check to ensure they are available options.• Variables are check for values that might cause
problems, such as division by zero.
![Page 81: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/81.jpg)
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Starting Out with C++, 3rd Edition
4.13 More About Variable Declarations and Scope
• The scope of a variable is limited to the block in which is is declared.
• Variables declared inside a set of braces have local scope or block scope.
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Starting Out with C++, 3rd Edition
Program 4-22A//This program demonstrates late variable declaration
#include <iostream.h>
void main(void)
{
cout << "What is your annual income? ";
float income; // variable declaration
cin >> income;
cout << "How many years have you worked at "
<< "your current job? ";
int years; // variable declaration
cin >> years;
if (income >= 35000 || years > 5)
cout << "You qualify.\n";
else
{
cout << "You must earn at least $35,000 or have\n";
cout << "been employed for more than 5 years.\n";
}
}
![Page 83: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/83.jpg)
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Starting Out with C++, 3rd Edition
Program 4-22B
//This program demonstrates late variable declaration
#include <iostream.h>
void main(void)
{
cout << "What is your annual income? ";
float income; // variable declaration
cin >> income;
cout << "How many years have you worked at "
<< "your current job? ";
int years; // variable declaration
cin >> years;
if (income >= 35000 || years > 5)
cout << "You qualify.\n";
else
{
cout << "You must earn at least $35,000 or have\n";
cout << "been employed for more than 5 years.\n";
}
}
![Page 84: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/84.jpg)
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Starting Out with C++, 3rd Edition
Program 4-22C
//This program demonstrates late variable declaration
#include <iostream.h>
void main(void)
{
cout << "What is your annual income? ";
float income;
cin >> income;
int years;
cout << "How many years have you worked at "
<< "your current job? ";
cin >> years;
if (income >= 35000 || years > 5)
cout << "You qualify.\n";
else
{
cout << "You must earn at least $35,000 or have\n";
cout << "been employed for more than 5 years.\n";
}
}
![Page 85: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/85.jpg)
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Starting Out with C++, 3rd Edition
Program 4-23// This program demonstrates a variable declared in an inner block. #include <iostream.h> void main(void){
cout << "What is your annual income? ";float income; // variable declarationcin >> income;if (income >= 35000){
int years; // variable declarationcout << "How many years have you worked at " << "your current job? ";cin >> years;if (years > 5)
cout << "You qualify.\n";
Program continues on next slide…
![Page 86: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/86.jpg)
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Program continued from previous slide.
else
{
cout << "You must have been employed for\n";
cout << "more than 5 years to qualify.\n";
}
}
else
{
cout << "You must earn at least $35,000 to\n";
cout << "qualify.\n";
}
}
![Page 87: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/87.jpg)
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Variables With the Same Name
• When a block is nested inside another block, a variable declared in the inner block may have the same name as a variable declared in the outer block. The variable in the inner block takes precedence over the variable in the outer block.
![Page 88: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/88.jpg)
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Starting Out with C++, 3rd Edition
Program 4-24// This program uses two variables with the name Number.
#include <iostream.h>
void main(void)
{
int number;
cout << "Enter a number greater than 0: ";
cin >> number;
if (number > 0)
{
int number;
Program continues on next slide…
![Page 89: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/89.jpg)
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Program continued from previous slide.
cout << "Now enter another number: ";
cin >> number;
cout << "The second number you entered was ";
cout << number << endl;
}
cout << "Your first number was " << number << endl;
}
![Page 90: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/90.jpg)
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Program Output with Example Input
Enter a number greater than 0: 2 [Enter]
Now enter another number: 7[Enter]
The second number you entered was 7
Your first number was 2
![Page 91: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/91.jpg)
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Starting Out with C++, 3rd Edition
4.14 Comparing Strings
• Use the strcmp library function to compare C-strings.
![Page 92: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/92.jpg)
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Program 4-25// This program illustrates that you cannot compare strings// with relational operators. Although it appears to test the// strings for equality, that is NOT what happens.#include <iostream.h>
void main(void){
char firstString[40], secondString[40]; cout << "Enter a string: ";
cin.getline(firstString, 40);cout << "Enter another string: ";cin.getline(secondString, 40);if (firstString == secondString)
cout << "You entered the same string twice.\n";else
cout << "The strings are not the same.\n";}
![Page 93: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/93.jpg)
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter a string: Alfonso [Enter]
Enter another string: Alfonso [Enter]
The strings are not the same.
![Page 94: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/94.jpg)
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Starting Out with C++, 3rd Edition
The strcmp Function
strcmp(string1, string2); // include cstring to use
// this function
• If the two strings are identical, strcmp returns 0.
• If string1 < string 2, strcmp returns a negative number.
• If string1 > string 2, strcmp returns a positive number.
![Page 95: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/95.jpg)
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Starting Out with C++, 3rd Edition
Program 4-26// This program correctly tests two strings for equality, with
// the strcmp function
#include <iostream.h>
#include <string.h>
void main(void)
{
char firstString[40], secondString[40];
cout << "Enter a string: ";
cin.getline(firstString, 40);
cout << "Enter another string: ";
cin.getline(secondString, 40);
if (strcmp(firstString, secondString) == 0)
cout << "You entered the same string twice.\n";
else
cout << "The strings are not the same.\n";
}
![Page 96: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/96.jpg)
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Starting Out with C++, 3rd Edition
Program 4-27
// This program uses strcmp to compare the sting entered
// by the user with the valid stereo part numbers.
#include <iostream.h>
#include <string.h>
void main(void)
{
const float aprice = 249.0, Bprice = 299.0;
char partNum[8];
cout << "The stereo part numbers are:\n";
cout << "\tBoom Box, part number S147-29A\n";
Program continues on next slide…
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Starting Out with C++, 3rd Edition
Program continued from previous slide
cout << "\tShelf Model, part number S147-29B\n";
cout << "Enter the part number of the stereo you\n";
cout << "wish to purchase: ";
cin.width(9); // So they won't enter more than 8 char's
cin >> partNum;
cout.setf(ios::fixed || ios::showpoint);
cout.precision(2);
if (strcmp(partNum, "S147-29A") == 0) // use of strcmp
cout << "The price is $" << aprice << endl;
else if (strcmp(partNum, "S147-29B") == 0)
cout << "The price is $" << Bprice << endl;
else
cout << partNum << " is not a valid part number.\n";
}
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98
Starting Out with C++, 3rd Edition
Program Output with Example Input
The stereo part numbers are:
Boom Box, part number S14729A
Shelf Model, part number S147-29B
Enter the part number of the stereo you
wish to purchase: S147-29B [Enter]
The price is $299.00
![Page 99: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/99.jpg)
99
Starting Out with C++, 3rd Edition
Program 4-28
// This program uses the return value of strcmp to
// alphabetically sort two strings entered by the user.
#include <iostream.h>
#include <string.h>
void main(void)
{
char name1[30], name2[30];
cout << "Enter a name (last name first): ";
cin.getline(name1, 30);
cout << "Enter another name: ";
cin.getline(name2, 30);
Program continues on next slide…
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Starting Out with C++, 3rd Edition
Program continued from previous slide.
cout << "Here are the names sorted alphabetically:\n";
if (strcmp(name1, name2) < 0)
cout << name1 << endl << name2 << endl;
else if (strcmp(name1, name2) > 0)
cout << name2 << endl << name1 << endl;
else
cout << "You entered the same name twice!\n";
}
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Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter a name (last name first): Smith, Richard [Enter]
Enter another name: Jones, John [Enter]
Here are the names sorted alphabetically
Jones, John
Smith, Richard
![Page 102: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/102.jpg)
102
Starting Out with C++, 3rd Edition
Program 4-29//This program uses strcmp to compare the string entered
//by the user with the valid stereo part numbers.
#include<iostream.h>
#include<string>
using namespace std;
void main(void)
{
const float aprice = 249.0, bprice = 299.0;
string partNum;
cout << "The stereo part numbers are:\n";
cout << "Boom box, part number S147-29A\n";
cout << "Shelf model, part number S147-29B\n";
cout << "Enter the part number of the stereo you\n";
cout << "wish to purchase: ";
cin >> partNum;
Program continues on next slide…
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Starting Out with C++, 3rd Edition
Program continued from previous slide
cout.setf(ios::fixed | ios::showpoint); cout.precision(2);
if (partNum == "S147-29A")
cout << "The price is $" << aprice << endl;
else if (partNum == "S147-29B")
cout << "The price is $" << bprice << endl;
else
cout << partNum << " is not a valid part number.";
}
![Page 104: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/104.jpg)
104
Starting Out with C++, 3rd Edition
Program Output with Example Input
The stereo part numbers are:
Boom box, part number S147-29A
Shelf model, part number S147-29B
Enter the part number of the stereo you
wish to purchase: S147-29A
The price is $249.00
![Page 105: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/105.jpg)
105
Starting Out with C++, 3rd Edition
4.15 The Conditional Operator
• You can use the conditional operator to create short expressions that work like if/else statements
expression ? result if true : result if false;
X < 0 ? Y = 10 : Z = 20;
![Page 106: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/106.jpg)
106
Starting Out with C++, 3rd Edition
Program 4-30// This program calculates a consultant's charges at $50 per hour,
// for a minimum of 5 hours. The ?: operator adjusts hours to 5 if less
// than 5 hours were worked.
#include <iostream.h>
void main(void)
{
const float payRate = 50.0;
float hours, charges;
cout << "How many hours were worked? ";
cin >> hours;
hours = hours < 5 ? 5 : hours;
charges = payRate * hours;
cout.precision(2);
cout.setf(ios::fixed | ios::showpoint);
cout << "The charges are $" << charges << endl;
}
![Page 107: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/107.jpg)
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Starting Out with C++, 3rd Edition
Program Output with Example Input
How many hours were worked? 10 [Enter]
The charges are $500.00
Program Output with Example Input
How many hours were worked? 2 [Enter]
The charges are $250.00
![Page 108: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/108.jpg)
108
Starting Out with C++, 3rd Edition
Program 4-31// This program uses the return value of strcmp to alphabetically
// sort two strings entered by the user.
#include <iostream.h>
#include <string.h>
void main(void)
{
char name1[30], name2[30];
cout << "Enter a name (last name first): ";
cin.getline(name1, 30);
Program continues on next slide…
![Page 109: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/109.jpg)
109
Starting Out with C++, 3rd Edition
Program continued from previous slide.
cout << "Enter another name: ";
cin.getline(name2, 30);
cout << "Here are the names sorted alphabetically:\n";
cout << (strcmp(name1, name2) <= 0 ? name1 : name2) << endl;
cout << (strcmp(name1, name2) > 0 ? name1 : name2) << endl;
}
![Page 110: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/110.jpg)
110
Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter a name (last name first): Smith, Richard [Enter]
Enter another name: Jones, John [Enter]
Here are the names sorted alphabetically
Jones, John
Smith, Richard
![Page 111: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/111.jpg)
111
Starting Out with C++, 3rd Edition
4.16 The switch Statement
• The switch statement lets the value of a variable or expression determine where the program will branch to.
![Page 112: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/112.jpg)
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Starting Out with C++, 3rd Edition
Program 4-32// The switch statement in this program tells the user
// something he or she already knows: what they just entered!
#include <iostream.h>
void main(void)
{
char choice;
cout << "Enter A, B, or C: ";
cin >> choice;
Program continues on next slide…
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Starting Out with C++, 3rd Edition
Program continues
switch (choice)
{
case 'A': cout << "You entered A.\n";
break;
case 'B': cout << "You entered B.\n";
break;
case 'C': cout << "You entered C.\n";
break;
default: cout << "You did not enter A, B, or C!\n";
}
}
![Page 114: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/114.jpg)
114
Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter A, B, or C: B [Enter]
You entered B.
Program Output with Different Example Input
Enter a A, B, or C: F [Enter]
You did not enter A, B, or C!
![Page 115: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/115.jpg)
115
Starting Out with C++, 3rd Edition
Program 4-33// The switch statement in this program tells the user
// something he or she already knows: what they just
// entered!
#include <iostream.h>
void main(void)
{
char choice;
cout << "Enter A, B, or C: ";
cin >> choice;
Program continues on next slide…
![Page 116: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/116.jpg)
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Starting Out with C++, 3rd Edition
Program continued from previous slide.
switch (choice)
{
case 'A': cout << "You entered A.\n";
case 'B': cout << "You entered B.\n";
case 'C': cout << "You entered C.\n";
default: cout << "You did not enter A, B, or C!\n";
}
}
![Page 117: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/117.jpg)
117
Starting Out with C++, 3rd Edition
Program Output with Example Input
Enter a A, B, or C: A [Enter]
You entered A.
You entered B.
You entered C.
You did not enter A, B, or C!
Program Output with Example Input
Enter a A, B, or C: C [Enter]
You entered C.
You did not enter A, B, or C!
![Page 118: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/118.jpg)
118
Starting Out with C++, 3rd Edition
Program 4-34// This program is carefully constructed to use the
// "fallthrough" feature of the switch statement.
#include <iostream.h>
void main(void)
{
int modelNum;
cout << "Our TVs come in three models:\n";
cout << "The 100, 200, and 300. Which do you want? ";
cin >> modelNum;
cout << "That model has the following features:\n";Program continues on next slide…
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119
Starting Out with C++, 3rd Edition
Program continues
switch (modelNum)
{
case 300: cout << "\tPicture-in-a-picture.\n";
case 200: cout << "\tStereo sound.\n";
case 100: cout << "\tRemote control.\n";
break;
default: cout << "You can only choose the 100,";
cout << "200, or 300.\n";
}
}
![Page 120: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/120.jpg)
120
Starting Out with C++, 3rd Edition
Program Output with Example Input
Our TVs come in three models:The 100, 200, and 300. Which do you want? 100 [Enter]That model has the following features:
Remote control.
Program Output with Example Input
Our TVs come in three models:The 100, 200, and 300. Which do you want? 200 [Enter]That model has the following features:
Stereo sound.Remote control.
![Page 121: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/121.jpg)
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Starting Out with C++, 3rd Edition
Program 4-35// The switch statement in this program uses the "fallthrough"
// feature to catch both upper and lowercase letters entered
// by the user.
#include <iostream.h>
void main(void)
{
char feedGrade;
cout << "Our dog food is available in three grades:\n";
cout << "A, B, and C. Which do you want pricing for? ";
cin >> feedGrade;
Program continues on next slide…
![Page 122: Starting Out with C++, 3 rd Edition 1 Chapter 4. Making Decisions.](https://reader030.fdocuments.in/reader030/viewer/2022032722/56649cea5503460f949b4d8b/html5/thumbnails/122.jpg)
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Starting Out with C++, 3rd Edition
Program continued from previous slide.
switch(feedGrade){
case 'a':case 'A': cout << "30 cents per pound.\n"; break;case 'b':case 'B': cout << "20 cents per pound.\n"; break;case 'c':case 'C': cout << "15 cents per pound.\n"; break;default: cout << "That is an invalid choice.\
n";}
}