Thread: validate isbn

fgw_three is right.

Code:

char code[15];
fgets(code,15,stdin);

When you store like this.The most significant digit is stored at code[0].

Code:

for(i=9;i>=0; i--)
	{
		if((i==9) && (toupper(*(code + i)) == 'x'))
			{
				value = 10;
			}
		else
			{
	 value = (int)(*(code + i)-48); \\\By this Yor are moving from least signicant to most significant.
			}
		sum += value * (i+1);\\here you are multiplying with 10 with least significant,9 with.... so on.Your are doin opposite.
	}