C++ while Loop

A while loop is another kind of loop control structure. The loop has initial condition and a test condition to pass before the actual loop body starts. The loop is incremented or decremented inside of the loop body.

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The general structure of while loop is given below.

initial expression;
while( test condition)
{
     do something;
     increment or decrement loop;
}

The initial expression is a simple assignment where a loop starts with 0 or 1. The test condition can be an expression, return from a function, or a constant. The loop is incremented or decremented inside the body of the loop.

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You can note the similarity between while loop and for loop, both contains 3 expressions. However, with while loop the initialization happens before the loop body starts.

Graphical Representation of while loop

A graphical representation is helpful when you create a flowchart of your C++ program. Here is the graphical representation of while loop.

while Loop Diagram
while Loop Diagram

Example Program:


//While loop
#include <cstdlib>
#include <iostream>
using namespace std;
int main()
{
    //variable declaration and initialization
    
    int number,i;
    int sum = 0;
    
    //read values and computing total 
    
    for(i = 0;i<5; i++)
    {
          cout << "Enter Number:";
          cin >> number;
          
          sum = sum + number;
    }
    
    //printing output 
    
    cout << "Sum = " << " " << sum << endl;
    
    system("PAUSE");
    return EXIT_SUCCESS;
}

Output:

Enter Number:23
Enter Number:55
Enter Number:66
Enter Number:67
Enter Number:76
Sum =  287


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