Exam-style question
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A direct-addressing instruction has an operand that identifies register R3. What is the role of R3 in this instruction?.
- A.It is the datum that must always be used without reading it.
- B.It is the address of the datum to be used.
- C.It is the address of the next instruction.
- D.It specifies that immediate addressing must be used instead.
Model answer
What a good answer should say
- It is the address of the datum to be used.
Explanation
Why this works
The specification allows an address to be interpreted as referring to main memory or a register. With direct addressing, the operand identifies where the datum is located, here register R3.
Common mistake
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