An integer number is divisible by 9 if the sum of its digits is divisible by 9.

1. Write a program that reads a positive integer, finds the number of digits of this integer and using the criteria above, discovers if it is divisible by 9 and then prints out the results.
   Example: if the user enters 57883
   The program displays :
   57883 has 5 digits.
   The sum of digits is : 31
   It is not divisible by 9
2. Write a program that uses the criteria above to display all the positive integers between 100 and 1000 that are divisible by 9.

#include<stdio.h>
int main()
{
	int n, nbdigits, sum, copy;

   	 do{
        	printf("Enter n: ");
        	scanf("%d", &n);
    	}while(n<=0);
	
	copy = n;
	nbdigits = sum=0;
	while(copy)
	{
	    nbdigits++;
	    sum+=copy%10;
	    copy/=10;
	}
	
	printf("%d has %d digits.\n",n,nbdigits);
	printf("The sum of digits is : %d\n",sum);
	if(sum%9)
	    printf("It is not divisible by 9\n");
	else
	    printf("It is divisible by 9\n");
	    
	return 0;
}


#include<stdio.h>
int main()
{
	int n, nbdigits, sum, copy;

	for(n=100;n<=1000;n++)
    	{
	    nbdigits = sum=0;
	    copy = n;
	    while(copy)
	    {
	        nbdigits++;
	        sum+=copy%10;
	        copy/=10;
	    }

	    if(sum%9==0)
	        printf("%d ",n);
    	}
	    
	return 0;
}