- 2069 Bhadra · 2 marks
2's complement: 15 − 20
Short answer
8-bit: 15 = 00001111, 20 = 00010100. 2's complement of 20 = 11101100. Add: 00001111 + 11101100 = 11111011, no carry, negative. 2's complement of result gives 00000101 = 5, so 15 − 20 = −5.
Find: (15)10 − (20)10 = ?, use 2's complement method.
Use 8-bit numbers.
- 15 = 00001111
- 20 = 00010100
- 1's complement of 20 = 11101011; add 1 gives the 2's complement 11101100.
- Add:
00001111 (15)
+ 11101100 (2's complement of 20)
----------
11111011
- No end carry, so the result is negative.
- Magnitude: 2's complement of 11111011 = 00000100 + 1 = 00000101 = 5.
Answer: 15 − 20 = −5
✓ Answer checked by Claude Opus 5.5 (high effort)
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