C++ While Loop

Structure of C++ while loop

This is the general structure of the while loop:

A simple example of using while loop in C++

In the following example, we will simply display numbers from 1 to 10 on screen. For that,

• We declared an int type variable x and assigned it an initial value of 1.
• In the while condition we set: x<=10 i.e. Keep on executing the while loop until the value of x is less than or equal to 10.
• Inside the curly brackets, we displayed the current value of x
• This is followed by incrementing the value of x by 1. So, in each iteration, the value is incremented by 1.

The code:

#include <iostream>

using namespace std;

int main() {

    int x = 1;

    while (x <= 10) {

        cout <<"Current value of x = " << x << "\n";

        x++;
    }

    return 0;
}

Output:

A program using a while loop with a decrement operator

In this program, we will display the numbers from 10 to 1. Have a look at the code and I will explain it later:

#include <iostream>

using namespace std;

int main() {

    int x = 10;

    while (x >= 1) {

        cout <<"Current value of x = " << x << "\n";
        x--;
    }

    return 0;

}

Output:

Display odd numbers between 1 to 20 by using C++ while loop

This example displays the odd number between 1 to 20 numbers.

First code and output:

#include <iostream>

using namespace std;

int main() {

    int x = 1;

    while (x <= 20) {

        cout <<"x = " << x << "\n";
        x=x+2;
    }

    return 0;
}

Output:

In the program:

• We initialized variable x= 1
• Set the condition to execute the while till x reaches 20
• In each iteration, we increment the value of x by 2 i.e. x = x + 2;

Using break statement in while loop example

This is generally required when a certain task is achieved while using a while loop.

To demonstrate that, the program below exits the while loop as the value of variable x is equal to 7.

#include <iostream>

using namespace std;

int main() {

    int x = 1;

    while (x <= 10) {

        cout <<"x = " << x << "\n";

        x=x+1;
        if (x == 7) {
          break;
    }
   }

    return 0;

}

output:

You saw this is just like the first example. Except we used an if condition where we checked the value of x.

As it is equal to 7, the break statement is executed, and while loop is exited. So, 7,8,9, and 10 did not display.

Learn more about break statement

An example of using a continue statement with while loop

In the following example, we will display numbers from 1 to 10 while omitting the numbers 3 and 7. Have a look:

#include <iostream>

using namespace std;

int main() {

    int x = 1;

    while (x <= 10) {

     if (x == 3 || x == 7){

        x=x+1;
        continue;
    }
        cout <<"x = " << x << "\n";
        x=x+1;
    }

    return 0;

}

Output:

You can see, the if condition is used to check the value of x. We used or operator (||) in the condition to check value = 3 and 7.

As the condition is true, the continue statement executed that omitted the current iteration of the while loop, and the value of x did not display for numbers 3 and 7.

An example of using a nested while loop

See an example of its usage below:

#include <iostream>

using namespace std;

int main () {

        int x=1;

        //Outer while loop

          while(x<=4)

          {

              int y = 1;

              //Inner while loop

              while (y <= 4)

{

            //Display current values of x and y

            cout<<x<<" "<<y<<"\n";

            y++;

          }

           x++;

        }

    }

An example of displaying the table of 15 by using while loop

The following program of C++ displays the table of 15 by using a while loop. Have a look at the code and output:

#include <iostream>

using namespace std;

int main() {

    int x = 1;

    int y = 15;

    while (y <= 150) {

        cout <<"15 * "<<x <<"   = " << y << "\n";

        x++;

        y=y+15;

    }

    return 0;

}

Output: