Dear Steph,

as you know microcontrollers are not designed for handling math operations on large numbers.

DIV instruction can only do 8 bit unsigned integer division. So you need a special sub-routine that calculate the desired value.

First way, you would check the book: "Embedded Applications Handbook", INTEL.
It includes both fixed point and floating poing math. operations. I can't send you example program since it's very long to type, and I don't have it in electronic form too. But probably you can find it on internet.

Second alternative: usually there are other ways to have the result without doing long calculations. If you explain your application maybe I can give you some other ideas (if you want).

I wish you success in your lessons.

Selim Dilmac
MSc. Electronics Engineer