Question

If accumulator contains the data ABH and register B contains 54H. ‘What will be the contents of accumulator in hexadecimal after execution of each of the instructions dependently (Stepwise, i.e., one after another.

1. ANA B
2. CMA
3. CMP B
4. ANI OOH

Answer 1

Initial: A = ABH, B = 54H.

1. ANA B, A ← A AND B.
ABH AND 54H = 00H, so Accumulator = 00H.

2. CMA, Complement accumulator (one's complement).
Complement of 00H = FFH, so Accumulator = FFH.

3. CMP B, Compare A with B (flags affected); the accumulator is not changed.
A remains FFH after CMP B. (Flags: since FFH > 54H, CY = 0 and Z = 0.)

ANI 00H, A ← A AND 00H (immediate).
FFH AND 00H = 00H, so Accumulator = 00H.

After ANA B: 00H

After CMA: FFH

After CMP B: FFH

After ANI 00H: 00H