Getting floating point exception while trying to use div in assembly

Question

I am trying to run the following code in assembly:

  mov        %si, %ax
  mov        $15, %si
  div        %si
  mov        %eax, %esi

When I make my program, it compiles, but at runtime it gives me a floating point exception. I tried to replace the last line's parameters by %ah and %si.

Briefly, I am trying to divide %esi by 15. I only want an int, and have no need for a double.

Thank you

Answer 1

The div instruction divides the two-word parameter dx/ax by the operand. If the quotient is too large to fit into a word, it will throw that exception.

Reference: http://siyobik.info.gf/main/reference/instruction/DIV

What do you have in the dx register? Most likely dx/ax divided by 15 does not fit in a 16-bit word.