The _____ addressing mode is similar to register indirect addressing mode,…
2016
The _____ addressing mode is similar to register indirect addressing mode, except that an offset is added to the contents of the register. The offset and register are specified in the instruction.
- A.
Base indexed
- B.
Base indexed plus displacement
- C.
Indexed
- D.
Displacement
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Correct answer: C
Answer: Indexed addressing mode.
Explanation: Indexed addressing (also called register indirect with displacement or base-plus-displacement) uses the contents of a register plus an immediate offset specified in the instruction to form the effective memory address.
Effective address = contents of the specified register + offset (displacement).
The instruction explicitly provides both the register and the offset.
Example format: LOAD Rdest, offset(Rbase) meaning load from memory address equal to contents of Rbase plus offset.
Why other choices are not correct:
Base indexed: typically uses a base register and an index register (two registers) rather than a single register plus an immediate offset.
Base indexed plus displacement: includes base register, index register, and displacement, which is more complex than the single-register-plus-offset mode described.
Displacement (by itself): is an ambiguous term; the precise name for the described mode is indexed or register indirect with displacement.