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:

while loop
do-while loop
for loop

The While Loop

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

Syntax

 while (condition) { statements; }

Flow Diagram:

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:

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:

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: