text: #include<stdio.h>
  #include<conio.h>
  int main()
  {
  	char isbn[15];
  	int i, sum = 0;
  	printf("\nEnter 10 digit ISBN number : ");
  	gets(isbn);
  	for (i = 0; i <= 9; i++)
  	{
  		isbn[i] -= 48;/*Converting characters into numerals*/
  		sum = sum + ((i + 1)*isbn[i]);/*checking the condition of the ISBN validity*/
  	}
  	if (sum % 11)/*If not divisble by 11*/
  		puts("\nISBN number is wrong.");
  	else
  		puts("\nISBN number is valid.");
  	_getch();
  	return 0;
  }
  