#include <stdio.h>#define ID_LENGTH 9
void main(void)
{
unsigned long id_buf,sum=0;
unsigned char mult = {1, 2, 1, 2, 1, 2, 1, 2, 1};
int i,tmp;
printf("Desired ID number : ");
i = scanf("%d", &id_buf);
for(i=0;i<ID_LENGTH;i++)
{
tmp = (id_buf % 10) * mult;
sum += tmp%10 + tmp/10;
id_buf /= 10;
}
if(sum % 10 == 0)
{
printf("The entered ID is correct.\n");
}
else
{
printf("The entered ID is incorrect.\n");
}
}