C++ Tutorial/Data Types/bool

A bool value can control the if statement

<source lang="cpp">#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; 

}</source>

b is 0
b is 1
This is executed.

bool values

<source lang="cpp">#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; 

}</source>

b is 0
b is 1
This is executed.
10 > 9 is 1

Logical operators.

<source lang="cpp">#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;

}</source>

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

<source lang="cpp">#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; 

}</source>

b is 0
b is 1
10 > 9 is 1

Output boolean variable as boolean literal or number

<source lang="cpp">#include <iostream>

1. 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;

}</source>

The !(Exclamation mark) Operator

<source lang="cpp">#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;

}</source>

The || Operator

<source lang="cpp">#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;

}</source>

The && Operator (amplifier)

<source lang="cpp">#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;

}</source>

Use bool value to control a while loop

<source lang="cpp">#include <iostream>

1. 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;

}</source>

Variable size of bool

<source lang="cpp">#include <iostream>

int main() {

  using std::cout;
 
  cout << "The size of a bool is:"      << sizeof(bool)   << " bytes.\n";
 
  return 0;

}</source>

The size of a bool is:1 bytes.