C Language while statement with example

In this post, we learn how to use while loop in C language

How while loops works

first the initialization statements are executed only once

Then the test expression is evaluated. When the test expression becomes false. The control comes out from the loop and wile loop is terminated.
However, when the test expression evaluated to true, statements inside the body of  while loop are executed.
finally, the updating statement(increment/decrement) is updated

then again the test expression is evaluated
This process happening on until the test expression becomes false.

program 1

 This program displays natural numbers from 1 to 9

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int num,i=1,sum=0;
    printf("Enter a number for find sum\n");
    scanf("%d",&num);
    while(i<=num){
        sum+=i;   //sum=sum+i
        i++;
    }

    printf("Sum of natural numbers 1 to %d is: %d",num,sum);
    getch();
    return 0;
}

Enter a number for find sum
100
sum of natural numbers 1 to 100 is: 5050

Nested while loop

while(condition) {

   while(condition) {
      statement(s);
   }

   statement(s);

}

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int i=0;
    int j=0;
    while(i<=10)
    {
        printf(“*”);
        printf(“n”);
j=0;
    while(j<=10)
    {
        printf(“*”);
        j++;
    }
    i++;

}


}

we can print a rectangular pattren using two while loop at the above program

When the above code is executed, it produces the following result