Question

The content of the registers are \( R_1 = 25H \), \( R_2 = 30H \), and \( R_3 = 40H \). The following machine instructions are executed. 

After execution, the content of registers \( R_1 \), \( R_2 \), \( R_3 \) are

• A. \( R_1 = 40H \), \( R_2 = 30H \), \( R_3 = 25H \)
• B. \( R_1 = 25H \), \( R_2 = 30H \), \( R_3 = 40H \)
• C. \( R_1 = 30H \), \( R_2 = 40H \), \( R_3 = 25H \)
• D. \( R_1 = 40H \), \( R_2 = 25H \), \( R_3 = 30H \)

Hint:

When using push and pop operations, remember that the stack operates in a last-in, first-out (LIFO) manner. The last value pushed is the first one to be popped.

Answer 1

The Correct Option is A

- Initially, the contents of the registers are: \[ R_1 = 25H, \, R_2 = 30H, \, R_3 = 40H. \] - After executing \( \texttt{PUSH\{R1\}} \), the value of \( R_1 \) is pushed onto the stack.
- After executing \( \texttt{PUSH\{R2\}} \), the value of \( R_2 \) is pushed onto the stack.
- After executing \( \texttt{PUSH\{R3\}} \), the value of \( R_3 \) is pushed onto the stack.
At this point, the stack has the values \( 40H, 30H, 25H \) in that order.
- After executing \( \texttt{POP\{R1\}} \), the top value (40H) is popped into \( R_1 \).
- After executing \( \texttt{POP\{R2\}} \), the next value (30H) is popped into \( R_2 \).
- After executing \( \texttt{POP\{R3\}} \), the next value (25H) is popped into \( R_3 \).
Thus, after the execution, the contents of the registers are: \[ R_1 = 40H, \, R_2 = 30H, \, R_3 = 25H. \] Final Answer: \( R_1 = 40H \), \( R_2 = 30H \), \( R_3 = 25H \)