A bool value can control the if statement
#include <iostream>
using namespace std;
int main() {
bool b;
b = false;
cout << "b is " << b << "\n";
b = true;
cout << "b is " << b << "\n";
if(b) cout << "This is executed.\n";
b = false;
if(b) cout << "This is not executed.\n";
return 0;
}b is 0
b is 1
This is executed.
bool values
#include <iostream>
using namespace std;
int main() {
bool b;
b = false;
cout << "b is " << b << "\n";
b = true;
cout << "b is " << b << "\n";
if(b) cout << "This is executed.\n";
b = false;
if(b) cout << "This is not executed.\n";
return 0;
}b is 0
b is 1
This is executed.
10 > 9 is 1
Logical operators.
#include <iostream>
using std::cout;
using std::endl;
using std::boolalpha; // causes bool values to print as "true" or "false"
int main()
{
// create truth table for && (logical AND) operator
cout << boolalpha << "Logical AND (&&)"
<< "\nfalse && false: " << ( false && false )
<< "\nfalse && true: " << ( false && true )
<< "\ntrue && false: " << ( true && false )
<< "\ntrue && true: " << ( true && true ) << "\n\n";
// create truth table for || (logical OR) operator
cout << "Logical OR (||)"
<< "\nfalse || false: " << ( false || false )
<< "\nfalse || true: " << ( false || true )
<< "\ntrue || false: " << ( true || false )
<< "\ntrue || true: " << ( true || true ) << "\n\n";
// create truth table for ! (logical negation) operator
cout << "Logical NOT (!)"
<< "\n!false: " << ( !false )
<< "\n!true: " << ( !true ) << endl;
return 0;
}Logical AND (&&)
false && false: false
false && true: false
true && false: false
true && true: true
Logical OR (||)
false || false: false
false || true: true
true || false: true
true || true: true
Logical NOT (!)
!false: true
!true: false
Outcome of a relational operator is a true/false value
#include <iostream>
using namespace std;
int main() {
bool b;
b = false;
cout << "b is " << b << "\n";
b = true;
cout << "b is " << b << "\n";
return 0;
}b is 0
b is 1
10 > 9 is 1
Output boolean variable as boolean literal or number
#include <iostream>
#include <iomanip>
using namespace std;
int main(int argc, char** argv)
{
bool myBool = true;
cout << "This is the default: " << myBool << endl;
cout << "This should be true: " << boolalpha << myBool << endl;
cout << "This should be 1: " << noboolalpha << myBool << endl;
}The !(Exclamation mark) Operator
#include <iostream>
using namespace std;
int main(void)
{
int age;
cout << "Enter your age: ";
cin >> age;
if (!(age > 12 && age < 65))
cout << "Admission is free";
else
cout << "You have to pay";
return 0;
}The || Operator
#include <iostream>
using namespace std;
int main(void)
{
int age;
cout << "Enter your age: ";
cin >> age;
if (age <= 12 || age >= 65)
cout << "Admission is free";
else
cout << "You have to pay";
return 0;
}The && Operator (amplifier)
#include <iostream>
using namespace std;
int main(void)
{
int age;
char choice;
bool citizen;
cout << "Enter your age: ";
cin >> age;
cout << "Are you a citizen (Y/N): ";
cin >> choice;
if (choice == "Y")
citizen = true;
else
citizen = false;
if (age >= 18 && citizen == true)
cout << "You are eligible to vote";
else
cout << "You are not eligible to vote";
return 0;
}Use bool value to control a while loop
#include <iostream>
#include <string>
using namespace std;
int main()
{
string best_name = "";
double best_price = 1;
int best_score = 0;
bool more = true;
while (more)
{
string next_name;
double next_price;
int next_score;
cout << "Please enter the model name: ";
getline(cin, next_name);
cout << "Please enter the price: ";
cin >> next_price;
cout << "Please enter the score: ";
cin >> next_score;
string remainder; /* read remainder of line */
getline(cin, remainder);
if (next_score / next_price > best_score / best_price)
{
best_name = next_name;
best_score = next_score;
best_price = next_price;
}
cout << "More data? (y/n) ";
string answer;
getline(cin, answer);
if (answer != "y") more = false;
}
cout << "The best value is " << best_name
<< " Price: " << best_price
<< " Score: " << best_score << "\n";
return 0;
}Variable size of bool
#include <iostream>
int main()
{
using std::cout;
cout << "The size of a bool is:" << sizeof(bool) << " bytes.\n";
return 0;
}The size of a bool is:1 bytes.
