An instruction at location 500 has its address field at 501, holding the value 400. Register R1 contains 200. Match each addressing mode with its effective address: (a) Direct, (b) Register indirect, (c) Indexed with R1 as index register, (d) Relative. Values: (i) 200, (ii) 902, (iii) 400, (iv) 600.

1. A(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
2. B(a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
3. C(a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)
4. D(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

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Correct answer: A. (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)

Explanation

Direct: 400. Register indirect: R1 = 200. Indexed: 400 + 200 = 600. Relative: PC (502 after fetch) + 400 = 902.