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GATE 2025 CS (CS1) – Question 37

Computer Organization and Architecture · Instruction Set and Addressing Modes · 2 marks · Multiple choice

A processor has 64 general-purpose registers and 50 distinct instruction types. An instruction is encoded in 32-bits. What is the maximum number of bits that can be used to store the immediate operand for the given instruction?

ADD R1, #25 // R1 = R1 + 25

  1. 16
  2. 20
  3. 22
  4. 24

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Correct answer: (B) 20

Explanation

The opcode needs ceil(log2 50) = 6 bits and the single register operand needs log2 64 = 6 bits. That leaves 32-6-6 = 20 bits for the immediate.