The advantage of _______ is that it can reference memory without paying the…
2014
The advantage of _______ is that it can reference memory without paying the price of having a full memory address in the instruction.
- A.
Direct addressing
- B.
Indexed addressing
- C.
Register addressing
- D.
Register Indirect addressing
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Correct answer: D
Answer: Register Indirect addressing
Why this is correct:
How it works: The instruction specifies a register that contains the effective memory address. The CPU uses the value in that register to access memory rather than encoding the full address in the instruction.
Main advantage: The instruction does not need to carry a full memory address, so instructions can be shorter and more flexible while still referencing memory.
Compared to direct addressing: Direct addressing encodes the full memory address inside the instruction, increasing instruction size. Register indirect avoids that by referring to a register.
Compared to indexed addressing: Indexed addressing uses a register plus a displacement (offset). It is useful for arrays but typically requires a displacement field in the instruction; register indirect only names a register holding the full address.
Compared to register addressing: Register addressing accesses data already in a register (no memory reference). That does not meet the question's intent of referencing memory without encoding a full memory address.
Trade-off: Register indirect requires a memory access to fetch the operand from the address stored in the register, so it is not as fast as pure register-to-register operations.
Example: LOAD R1, (R2) — load into R1 the value from the memory address contained in R2.
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