FP Addition and Subtraction Algorithm

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The following figure shows the algorithm for binary floating-point addition and subtraction. It includes the following five steps:

Step 1. Making exponents of two operands equal

Step 2. Adding or subtracting the significands

Step 3. Normalizing the result

Step 4. Rounding the significand

Step 5. Checking for overflow or underflow

• The subtraction uses the addition hardware by converting the subtrahend to 2’s complement representation.


• If rounding causes the result to be unnormalized, we must repeat Step 3.


• For single precision, the maximum exponent is 127, and minimum exponent is -126. The limits for double precision are 1023 and -1022.