Question

Consider the following assembly language program for a hypothetical processor. A, B and C are 8 bit registers. The meanings of various instructions are shown as comments.

MOV B, #0 ; B $\leftarrow$ 0

MOV C, #8 ; C $\leftarrow$ 8

Z : CMP C, #0 ; Compare C with 0

JZ X ; Jump to X if 0 flag is set

SUB C, #1 ; C $\leftarrow$ C - 1

RRC A, #1 ; Rotate right A through carry by one bit

JC Y ; Jump to Y if any carry flag is set

JMP Z ; Jump to Z

Y : ADD B, #1 ; B $\leftarrow$ B + 1

JMP Z ; Jump to Z

X:

Which of the following instructions when inserted at location X will ensure that the value of region. A after program execution is the name as the initial value?

• A. NOP ; no operation
• B. LRC A, #1 ; left rotate A through carry flag by one bit
• C. ADD A, #1
• D. RRC A, #1

Answer 1

The correct option is D RRC A, #1

RRC A, #1