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C++ - While Loop



A loop statement allows a program to execute a given block of codes repeatedly under a given condition. This enables a programmer to write programs in fewer lines of code and enhance the code readability. C++ has following types of loop to handle the looping requirements:

The While Loop

While loop allows a set of statements to be executed repeatedly until a given condition is true. The While loop can be viewed as a repeating if statement.

Syntax

while (condition) {
  statements;
}

Flow Diagram:

C++ While Loop

In below mentioned example, program uses while loop to sum all integers from 1 to 5.

#include <iostream>
using namespace std;
 
int main (){
  int i = 1;
  int sum = 0;
  while (i < 6){
    sum = sum + i;
    i = i+1;
  }
  cout<<sum; 
  return 0;
}

The output of the above code will be:

15

The Do-While Loop

The Do-While loop in C++ is a variant of while loop which execute statements before checking the conditions. Therefore the Do-While loop executes statements at least once.

Syntax

do {
  statements;
}
while (condition);

Flow Diagram:

C++ While Loop

In the example below, even if the condition is not fulfilled, the do-while loop executes the statements once.

#include <iostream>
using namespace std;
 
int main (){
  int i = 10;
  int sum = 0;
  do {
    sum = sum + i;
    i = i+1;
  } while (i < 6);
  
  cout<<sum; 
  return 0;
}

The output of the above code will be:

10

5