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Number Representation and Arithmetic

GATE CSE 2022 · Q41

MCQ2 marksMedium

Time

Consider three floating point numbers AA, BB and CC stored in registers RA\text{R}_\text{A}, RB\text{R}_\text{B} and RC\text{R}_\text{C}, respectively as per IEEE-754 single precision floating point format. The 32-bit content stored in these registers (in hexadecimal form) are as follows. Which one of the following is FALSE?

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Solution

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Official answer: B) C = A + B

Number Representation and Arithmetic

In IEEE-754 single-precision format, the 32 bits are divided as follows:

  • 1 sign bit (SS)

  • 8 exponent bits (EE) with bias 127127

  • 23 mantissa/fraction bits (MM)

The value is given by (−1)S×1.M×2E−127(-1)^S \times 1.M \times 2^{E - 127}.

  1. For register RA=0xC1400000\text{R}_\text{A} = \text{0xC1400000}:

    • In binary: 1 10000010 10000000000000000000000

    • Sign bit S=1S = 1 (negative)

    • Exponent E=(10000010)2=13010  ⟹  E−127=3E = (10000010)_2 = 130_{10} \implies E - 127 = 3

    • Mantissa M=0.12=0.510  ⟹  1.M=1.5M = 0.1_2 = 0.5_{10} \implies 1.M = 1.5

    • Value A=−1×1.5×23=−1.5×8=−12A = -1 \times 1.5 \times 2^3 = -1.5 \times 8 = -12

  2. For register RB=0x42100000\text{R}_\text{B} = \text{0x42100000}:

    • In binary: 0 10000100 00100000000000000000000

    • Sign bit S=0S = 0 (positive)

    • Exponent E=(10000100)2=13210  ⟹  E−127=5E = (10000100)_2 = 132_{10} \implies E - 127 = 5

    • Mantissa M=0.0012=0.12510  ⟹  1.M=1.125M = 0.001_2 = 0.125_{10} \implies 1.M = 1.125

    • Value B=+1×1.125×25=1.125×32=36B = +1 \times 1.125 \times 2^5 = 1.125 \times 32 = 36

  3. For register RC=0x41400000\text{R}_\text{C} = \text{0x41400000}:

    • In binary: 0 10000010 10000000000000000000000

    • Sign bit S=0S = 0 (positive)

    • Exponent E=(10000010)2=13010  ⟹  E−127=3E = (10000010)_2 = 130_{10} \implies E - 127 = 3

    • Mantissa M=0.12=0.510  ⟹  1.M=1.5M = 0.1_2 = 0.5_{10} \implies 1.M = 1.5

    • Value C=+1×1.5×23=1.5×8=12C = +1 \times 1.5 \times 2^3 = 1.5 \times 8 = 12

Evaluating the options:

  • (A) A+C=−12+12=0A + C = -12 + 12 = 0 (True)

  • (B) C=A+B  ⟹  12=−12+36=24C = A + B \implies 12 = -12 + 36 = 24, which is false (12≠2412 \neq 24)

  • (C) B=3C  ⟹  36=3×12=36B = 3C \implies 36 = 3 \times 12 = 36 (True)

  • (D) (B−C)=36−12=24>0(B - C) = 36 - 12 = 24 > 0 (True)

Therefore, statement B is FALSE.

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This Number Representation and Arithmetic previous year question is Q41 of the GATE CSE 2022 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. 4 of them are 2-mark MCQs like this one, and GATE CSE 2022 has 2.

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GateAI solution cardGATE CSE 2022 · Q41 · MCQ

Consider three floating point numbers A, B and C stored in registers RA, RB and RC, respectively as per IEEE-754 single precision floating point format. The 32-bit content stored in these registers (in hexadecimal form) are as follows. Which one of the following is FALSE?

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