Radix Complement Arithmetic (3)
Case 2: A = B - C
- A = (B)2 + (-(C)2) = (B)2 + [C]2 = (B)2 + 2n - (C)2 = 2n + (B - C)2
- If B ³ C, then A ³ 2n and the carry is discarded.
- So, (A)2 = (B)2 + [C]|carry discarded
- If B < C, then A = 2n - (C - B)2 = [C - B]2 or A = -(C - B)2 (no carry in this case).
- No overflow for Case 2.
- Example: (14)10 - (9)10 = ?
- Perform (14)10 + (-(9)10)
- (14)10 = +(1110)2 = (0, 1110)2cns
- -(9)10 = -(1001)2 = (1, 0111)2cns
- (14)10 - (9)10 = (0, 1110)2cns + (1, 0111)2cns = (0, 0101)2cns + carry