Given only putchar (no sprintf, itoa, etc.) write a routine putlong that prints out an unsigned long in decimal

void putlong(unsigned long x)  
{  
// we know that 32 bits can have 10 digits. 2^32 = 4294967296  
for (unsigned long y = 1000000000; y > 0; y /= 10) {  
putchar( (x / y) + '0');  
x = x % y;  
}  
}