F-P add (details for round-off omitted)
1. Compare exponents . If e1 < e2, swap the 2 operands such that
d = e1 - e2 >= 0. Tentatively set exponent of result to e1.
2. Insert 1’s at left of mantissas. If the signs of operands differ, replace 2nd mantissa by its 2’s complement.
3. Shift 2nd mantissa d bits to the right (inserting 0’s if not complemented, 1’s if it were).
4. Add the (shifted) mantissas. (there is one case where the result could be negative and you have to take the 2’s complement; this can happen only when d = 0 and the signs of the operands are different)
5. Normalize (if there was a carry-out in step 4, shift right once; else shift left until the first “1” appears on msb)
6. Modify exponent to reflect the number of bits shifted in previous step