Make sure all the variables you need to have fractional bits are floats (ie put a # after the variable name), and also note that when you do division with a constant number, you have to write it with a decimal place after to make sure the division is done as a floating point number, ie:
2/x will round off if x is an int
but
2.0/x will give a floating point number.
2/x will round off if x is an int
but
2.0/x will give a floating point number.