What to do: 1 Initialize x to be zero 2 Prompt the user for the next operation (

Question

What to do:
1 Initialize x to be zero

2 Prompt the user for the next operation (Addition or Subtraction)

3 Prompt the user for the next operand (y).

4 Perform the operation (x + y or x – y depends on the operation selected by
the user), and store back the result to x.

5 Output x in decimal.

6 Go back to step 2 until user input “q” as the next operation, then exit.


• Operations:
• Addition: perform x = x + y (when user input “+”)
• Subtraction: perform x = x - y (when user input “-”)
• quit: (when user input “q”).


• Operands:
• One operand (x) is initialized to be zero (defined in .data), and updated as
  the result; the other operand is always provided by the user


• Output:
• Decimal value of the current result (x).


• Extra credit:
• Include integer multiplication (*) and division (/) operations
-perform x = x * y (when user input “*”), and output the product.
- perform x = x / y (when user input “/”), and output both the
  quotient and remainder. In this case, x needs to be updated as the
  quotient.

Explanation / Answer

State         word State0
StateMach proc
                jmp State

; If this is state 0, add BX to AX and switch to state 1:

         State0: add ax, bx           ;addition
         mov x, ax                       ;result store in x
         mov State, offset State1 ;Set it to state 1
         ret

; If this is state 1, subtract BX from AX and switch to state 2

        State1: sub ax, bx            ; subtract
        mov x, ax                        ;result store in x
        mov State, offset State2  ;Switch to State 2
         ret

; If this is state 2, multiply AX and BX and switch to state 3:

       State2: push dx
       mul bx
       pop dx
       mov x, dx                        ;result store in x
       mov State, offset State3  ;Switch to State 3
       ret

; If in State 3, do the division and switch back to State 0:

       State3: push dx
       xor dx, dx                        ;Zero extend AX into DX.
       div bx
       pop dx
       mov x, dx                         ;result store in x
       mov State, offset State4   ;Switch to State 0
       ret

      state4: hlt                          ;Exit

StateMach endp

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