simple Longitudinal redundancy check

// Longitudinal redundancy check
char checksum(char* s)
{
	char sum = 0;
	while (*s != 0)
	{
		sum ^= *s;
		s++;
	}
	return sum;
}
 
char checksumData(char* data, const int size)
{
	char sum = 0;
	int l = size;
	while (l != 0)
	{
		sum ^= *data;
		data++;
		l--;
	}
	return sum;
}
 
int main()
{
	char s[] = "Hello world!\n";
	char sum = checksum(s);
	printf("%dn", sum);
	sum = checksumData(s, 13);
	printf("%dn", sum);
	return 0;
}