long int division

I need a 100% accurate division of any tow 32 bit numbers. So I am using the following code and the (/) operator.
However I notice that results are not accurate when the Den (denominator) is shorter that 32 bit.
For example (98765432/01234567) gives 120 where as the correct answer is 80.
Can anyone tell me why ? Is something in my code incorrect More important, if this is not a bug, how to fix it ?

Incidentally, I cannot use Printf function so I am using a union function to map the long int variables into 4 unsigned char and the Display the char via a serial port.
I don't think that process has introduced any errors in the calculations.

Thanks.

Bhal Tulpule

unsigned long int xdata Num,Den,Res;
Num = 98765432;
Den = 1234567;
Res = Num/Den;
//Display Res;