The smallest integer that can be represented by an 8-bit number in 2's…

2013

The smallest integer that can be represented by an 8-bit number in 2's complement form is

  1. A.

    −256

  2. B.

    −128

  3. C.

    −127

  4. D.

    0

Attempted by 18 students.

Show answer & explanation

Correct answer: B

Concept

In an n-bit two's complement representation, the most significant bit is the sign bit, and the representable integers form the range −2n−1 to 2n−1 − 1. The range is asymmetric: there is exactly one extra negative value because the single zero pattern frees one code on the positive side.

Application

  1. Here n = 8, so the lower bound is −28−1 = −27.

  2. Evaluate the power: 27 = 128, so the smallest (most negative) value is −128.

  3. The upper bound is 27 − 1 = 127, giving the full range −128 to 127.

Cross-check

Count the patterns: 8 bits give 28 = 256 codes. These cover −128, …, −1 (128 negatives), 0, and 1, …, 127 (127 positives): 128 + 1 + 127 = 256. The count matches, confirming the smallest value is −128.

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