Nested While Loop in C

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Nested While Loop in C Programming Language with Examples

In this article, I will discuss Nested While Loop in C Programming Language with Definitions, Syntax, Flow Charts, and Examples. Please read our previous article, where we discussed While Loop in C Language with Examples.

Nested While Loop in C Programming Language:

Writing while loop inside another while loop is called nested while loop, or you can say defining one while loop inside another while loop is called nested while loop. That is why nested loops are also called “loops inside the loop”. There can be any number of loops inside one another with any of the three combinations depending on the complexity of the given problem.

When we need to repeat the loop body itself “n” number of times, then we need to go for nested loops. Nested loops can be designed for up to 255 blocks.

Nested While Loop Syntax in C Language:

Following is the syntax to use the nested while loop in C language.

Note: In the nested while loop, the number of iterations will be equal to the number of iterations in the outer loop multiplied by the number of iterations in the inner loop, which is almost the same as the nested for loop. Nested while loops are mostly used for making various pattern programs in C, like number patterns or shape patterns.

Execution Flow of Nested While Loop in C Language:

The outer while loop executes based on the outer condition, and the inner while loop executes based on the inner condition. Now, let us understand how the nested while loop executes. First, it will check the outer loop condition; if the outer loop condition fails, it will terminate the loop.

Suppose the outer loop condition is true, then it will come inside. First, it will print the outer loop statements, which are there before the inner loop. Then, it will check the inner loop condition. If the inner while condition is true, then the control moves inside and executes the inner while loop statements. After the execution of inner while loop statements, again, it will check the inner while loop condition because it is a loop and as long as the condition is true, it will repeat this process. Once the inner while loop condition fails, the control moves outside and executes the statements that are present after the inner while loop. Once it executes, then again, it will go and check the outer while loop condition. And if it is true, then it will again execute the same process.

So, when the loop will terminate means when the outer while loop condition becomes false.

Flow Chart of Nested While Loop:

Please look at the following diagram, which represents the nested while loop flow chart.

The flow will start, and first, it will check the outer while loop condition. And if the outer while loop condition fails, it will end. Suppose the outer loop condition is true. Then, it will execute the outer while loop statements, if any. After execution of Outer while loop statements, it will check the inner while loop condition. For the inner while loop condition, it will also check for true and false. Suppose the inner while loop condition is true; then, inner while loop statements are executed. After executing the inner while loop statements, it will again check the inner while loop condition, and this inner loop execution process will repeat as long as the inner while loop condition is true. If the inner while loop condition is false, the remaining outer loop statements are executed. Once the outer loop statements are executed, then again, it will come and check the outer while condition. This is the flow of the nested while loop.

Example to print the following format.

#include <stdio.h>
int main ()
{
    int i, n, in;
    printf ("ENTER  A NUMBER ");
    scanf ("%d", &n);
    i = 1;
    while (i <= n)
    {
      printf ("\n");
      in = 1;
      while (in <= i)
   {
     printf ("%d ", in);
     in = in + 1;
   }
      i = i + 1;
    }
    return 0;
}

Example to print the following format:

#include <stdio.h>
int main()
{
    	int i, n, dn;
    	printf("ENTER  A NUMBER ");
    	scanf("%d", &n);
    	i = n;
    	while(i >= 1)
    	{
        		printf("\n");
        		dn = i;
        		while(dn >= 1)
        		{
                		printf("%d ", dn);
                		dn = dn - 1;
        		}
        		i = i - 1;
    	}    
    	return 0;
}

Example to print the following format:

#include <stdio.h>
int main ()
{
    int a = 1, b = 1;
    while (a <= 5)
    {
       b = 1;
       while (b <= 5)
    {
       printf ("%d ", b);
       b++;
    }
       printf ("\n");
       a++;
    }
    return 0;
}

In the next article, I am going to discuss Do While Loop in C Language with Examples. Here, in this article, I try to explain the Nested While Loop in C Programming Langauge with Examples. I hope you enjoy this Nested While Loop in C Programming Langauge with Examples article. I would like to have your feedback. Please post your feedback, questions, or comments about this article.