The following two signed 2’s complement numbers (multiplicand M and multiplier…
2025
The following two signed 2’s complement numbers (multiplicand M and multiplier Q) are being multiplied using Booth’s algorithm:
M: 1100 1101 1110 1101 and Q: 1010 0100 1010 1010
The total number of addition and subtraction operations to be performed is ___________. (Answer in integer)
Attempted by 93 students.
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Correct answer: 13
Final answer: 13 total operations (6 additions and 7 subtractions).
Reasoning:
Booth's algorithm examines pairs (q_i, q_{i-1}) for i = 0..15 after appending q_{-1} = 0. If the pair is 01, add the multiplicand; if 10, subtract the multiplicand; if 00 or 11, do nothing.
Write the multiplier bits from LSB to MSB and inspect each pair (q_i, q_{i-1}):
i=0: (0, 0) -> no operation
i=1: (1, 0) -> subtract
i=2: (0, 1) -> add
i=3: (1, 0) -> subtract
i=4: (0, 1) -> add
i=5: (1, 0) -> subtract
i=6: (0, 1) -> add
i=7: (1, 0) -> subtract
i=8: (0, 1) -> add
i=9: (0, 0) -> no operation
i=10: (1, 0) -> subtract
i=11: (0, 1) -> add
i=12: (0, 0) -> no operation
i=13: (1, 0) -> subtract
i=14: (0, 1) -> add
i=15: (1, 0) -> subtract
Count: additions = 6, subtractions = 7, total = 13.
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