Question

The expression \( X = (A+B) \times (C+D) \) has been evaluated using two address instructions method. The following is the set of instructions used.

MOV R1, A 
(B) MUL R1, R2 
(C) MOV R2, C 
(D) ADD R2, D 
(E) MOV X, R1 
 \(\textbf{Choose the correct sequence of instruction execution from the options given below:}\)

• A. A, B, C, D
• B. A, C, B, D
• C. B, A, D, C
• D. C, B, D, A

Hint:

In two-address instructions, operations are performed on the contents of registers, and the result is stored back into a register. The order of operations is crucial.

Answer 1

The Correct Option is B

Step 1: Understand the Expression.
We are given the expression \( X = (A+B) \times (C+D) \), and we are using two-address instructions. This involves loading operands into registers, performing operations on them, and storing the result in a final variable.

Step 2: Instruction Breakdown.
- (A) MOV R1, A: Load the value of \( A \) into register \( R1 \).
- (C) MOV R2, C: Load the value of \( C \) into register \( R2 \).
- (B) MUL R1, R2: Multiply the values in \( R1 \) and \( R2 \), and store the result in \( R1 \). This gives \( A \times C \).
- (D) ADD R2, D: Add the value of \( D \) to register \( R2 \) which currently holds the value of \( C \), so it becomes \( C + D \).
- (E) MOV X, R1: Store the result from \( R1 \) (which contains \( A \times C \)) into the variable \( X \).

Step 3: Execution Order.
The correct sequence of instructions to compute the expression \( (A+B) \times (C+D) \) using two-address instructions is:
1. First, load \( A \) into \( R1 \) (A). 2. Then, load \( C \) into \( R2 \) (C). 3. Perform the multiplication \( A \times C \) (B). 4. Add \( D \) to \( C \) (D). 5. Store the result of multiplication into \( X \) (E).

Step 4: Conclusion.
The correct sequence is (2) A, C, B, D. Therefore, the correct answer is option (2).