while loop in C++

Reading time: 20 minutes

Syntax :

While (condition)
{
   statement(s);
   Incrementation;
}

NOTE : Key point of the while loop is that the loop might not ever run. When the condition is tested and the result is false, the loop body will be skipped and the first statement after the while loop will be executed.

How while loop works

1. Condition is evaluated first.

2. If it returns true then the statements inside while loop execute.

3. Step 2 happens repeatedly until the condition returns false.

4. When condition returns false, the control comes out of loop and jumps to the next statement in the program after while loop.

Infinite while loop

A while loop that never stops is said to be the infinite while loop.
When we give the condition in such a way so that it never returns false, then the loops becomes infinite and repeats itself indefinitely.
An example of infinite while loop:
This loop would never end as I’m decrementing the value of i which is 1 so the condition i<=6 would never return false.

#include <iostream>
using namespace std;

int main()
{
   int i=1; 
   while(i<=6) 
   {
      cout<<"Value of variable i is: "<<i<<endl; i--;
   }
   return 0;
}

Example

#include <iostream>
using namespace std;
 
int main () 
{
   // Local variable declaration:
   int a = 10;

   // while loop execution
   while( a < 20 ) 
   {
      cout << "value of a: " << a << endl;
      a++;
   }
 
   return 0;
}

Output :

value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 15
value of a: 16
value of a: 17
value of a: 18
value of a: 19

Question

Consider this C++ code:

#include <stdio.h>
void main()
{
    int i = 0;
    while (++i)
    {
        cout<<"H";
    }
}