Specify the contents of the accumulator and the status of the S, Z and CY…

2014

Specify the contents of the accumulator and the status of the S, Z and CY flags when 8085 microprocessor performs addition of 87 H and 79 H.

  1. A.

    11, 1, 1, 1

  2. B.

    10, 0, 1, 0

  3. C.

    01, 1, 0, 0

  4. D.

    00, 0, 1, 1

Attempted by 77 students.

Show answer & explanation

Correct answer: D

Solution: step-by-step calculation and flags.

  1. Add the two hex values: 87H + 79H = 100H.

  2. Accumulator (8-bit result): take the low 8 bits of 100H, which is 00H.

  • Sign flag (S): 0, because the MSB of the result 00H is 0.

  • Zero flag (Z): 1, because the 8-bit result is 00H.

  • Carry flag (CY): 1, because the sum produced a carry out (100H > FFH).

Final answer: Accumulator = 00H; S = 0; Z = 1; CY = 1.

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