More Questions from Operating Systems Concepts

Addressing modes in computer architecture In which addressing mode is the memory address of the operand given explicitly within the instruction itself?

Computer Science Operating Systems Concepts Difficulty: Easy
Choose an option
  • A
    Absolute mode
  • B
    Immediate mode
  • C
    Index mode
  • D
    Modulus mode
  • E
    None of the above

Answer

Correct Answer: Absolute mode

Explanation

Introduction / Context:Addressing modes define how instructions reference their operands. Recognizing the differences helps with assembly programming, compiler design, and understanding generated machine code.

Given Data / Assumptions:

  • We compare absolute (direct) addressing against immediate and indexed addressing.
  • “Explicitly given address” means the instruction contains the target memory address as an operand field.
  • Terminology: absolute mode is also called direct mode in many texts.

Concept / Approach:

Absolute addressing places the effective memory address directly in the instruction. Immediate mode embeds the data value, not an address. Index mode combines a base (often from a register) with an offset to compute the effective address at run time.

Step-by-Step Solution:

Interpret the phrase “address of the location of the operand is given explicitly”.Match that phrase to absolute (direct) addressing where EA = address field.Eliminate immediate mode (EA not used; operand is a literal) and index mode (EA computed as base + index).Select Absolute mode.

Verification / Alternative check:

Assembly examples often show instructions like “LOAD A, 1000h” using direct addressing where 1000h is the memory address; this is absolute mode.

Why Other Options Are Wrong:

b: Immediate places the operand value in the instruction, not its address. c: Index computes an address from components at run time, not a single explicit address. d: “Modulus mode” is not a standard addressing mode.

Common Pitfalls:

Confusing “immediate value” with “address given immediately”; the former is data, not a pointer.

Final Answer:

Absolute mode

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