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Number Representation and Arithmetic

GATE CSE 2021 Set 2 · Q4

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The format of the single-precision floating-point representation of a real number as per the IEEE 754 standard is as follows: Which one of the following choices is correct with respect to the smallestsmallest normalized positive number represented using the standard?

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Solution

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Official answer: C) exponent = 00000001 and mantissa = 00000000000000000000000

Number Representation and Arithmetic

In the IEEE 754 single-precision (32-bit) floating-point format:

  • Sign bit (SS): 1 bit

  • Biased Exponent (EE): 8 bits

  • Fraction/Mantissa (MM): 23 bits

For normalized numbers:

  • The biased exponent EE ranges from 11 to 254254 (E=000000012E = 00000001_2 to 11111110211111110_2). E=0E = 0 is reserved for subnormal numbers and zero, while E=255E = 255 is reserved for ±∞\pm\infty and NaN.

  • The real value represented is given by:

    (−1)S×2E−127×(1.M)2(-1)^S \times 2^{E - 127} \times (1.M)_2

To represent the smallest normalized positive number:

  1. The sign bit is S=0S = 0 (positive).

  2. The exponent EE must be the smallest non-zero exponent: E=1E = 1 (00000001200000001_2).

  3. The mantissa MM must be the smallest possible fraction: all zeros, i.e., M=000000000000000000000002M = 00000000000000000000000_2.

This gives the value:

21−127×(1.0)2=2−126≈1.175494×10−382^{1 - 127} \times (1.0)_2 = 2^{-126} \approx 1.175494 \times 10^{-38}

Hence, exponent=00000001\text{exponent} = 00000001 and mantissa=00000000000000000000000\text{mantissa} = 00000000000000000000000, which corresponds to Option C.

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This Number Representation and Arithmetic previous year question is Q4 of the GATE CSE 2021 Set 2 paper. Find more GATE CSE PYQs on Number Representation and Arithmetic in Digital Logic, or browse all GATE CSE PYQs.

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Number Representation and Arithmetic in GATE CSE

Number Representation and Arithmetic has 33 GATE CSE PYQs across 20 papers from 2012 to 2026. 13 of them are 1-mark MCQs like this one, and GATE CSE 2021 Set 2 has 2.

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The format of the single-precision floating-point representation of a real number as per the IEEE 754 standard is as follows: Which one of the following choices is correct with respect to the smallest normalized positive number represented using the standard?

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