I need help coding this lc3 assembly program. Basically I need to make a calcula

Question

I need help coding this lc3 assembly program. Basically I need to make a calculator using LC3 assembly language and perform + - * and / operations.

**For the division operation I need to output both the quotient and remainder.

I have a skeleton:

   .ORIG   x3000

   and r1, r1, #0
   lea r0, Prompt
   puts
   getc
   out
   st r0, op
   ld r1, PLUS
   add r1, r0, r1
   brz addition
   ;;
   ld r1, MINUS
   add r1, r0, r1
   brz subtraction
   ;;
   ld r1, MULT
   add r1, r0, r1
   brz multiplication
   ;;
   ld r1, DIV
   add r1, r0, r1
   brz division
;
; If we are here, we got an invalid operation.
; Display error & exit
;
   lea r0, ErrMsg
   puts
   br done
   ;;
addition
   ;;setup
   ;;Do the addition. You can call a subroutine to add
  
   br output
subtraction
   ;; setup
   ;; Do the subtraction. You can call a subroutine to subtract
   br output
multiplication
   ;; Setup
   ;; jsr Multiply
   br output
division
   ;; Setup
   ;; jsr Divide
   br output
   ;;
output
   ;; Display result
   br done

done   halt
  
PLUS   .FILL #-43
MINUS   .FILL #-45
MULT   .FILL #-42
DIV   .FILL #-47
Prompt   .STRINGZ "Operation (+, -, *, /)? "
ErrMsg   .STRINGZ " Invalid Operation. "
op   .FILL #0
   .end
  

Any help will be appreciated!!
Thanks

Explanation / Answer

initializes all registers to zero
AND R0, R0, #0
AND R1, R1, #0
AND R2, R2, #0
AND R3, R3, #0
AND R4, R4, #0
AND R5, R5, #0
AND R6, R6, #0
AND R7, R7, #0

NEXTCHARACTER GETC
OUT

;Space?
LD R1, OPPOSPACE
ADD R1, R0, R1
BRz NEXTCHARACTER

;New line?
LD R1, OPPOLINE
ADD R1, R0, R1
BRz DONE

;Multiplication?
LD R1, OPPOMULTI
ADD R1, R0, R1
BRz DECODE
Brn INVALID_CHARACTER
LD R1, OPPODECI
ADD R1, R1, R0
BRz INVALID_CHARACTER

;Operand or operator?
LD R1, OPPOZERO
ADD R1, R1, R0
BRzp PUSH
BRn DECODE
  
ADDITION ADD R2, R5, #0   
LDR R5, R6, #0
ADD R6, R6, #1
ADD R3, R5, #0   
ADD R2, R2, R3   
ADD R6, R6, #-1   
STR R2, R6, #0
BRnzp NEXTCHARACTER   

SUBTRACTION ADD R3, R5, #0   
LDR R5, R6, #0
ADD R6, R6, #1
ADD R2, R5, #0   
NOT R3, R3
ADD R3, R3, #1
ADD R2, R2, R3
ADD R6, R6, #-1   
STR R2, R6, #0
BRnzp NEXTCHARACTER

MULTIPLICATION ADD R2, R5, #0   
LDR R5, R6, #0
ADD R6, R6, #1
ADD R3, R5, #0   

MULTIPLICATIONLOOP ADD R2, R3, R2
ADD R3, R3, #-1
BRp MULTIPLICATIONLOOP
ADD R6, R6, #-1
STR R2, R6, #0
BRnzp NEXTCHARACTER   
DIVISION ADD R3, R5, #0
LDR R5, R6, #0
ADD R6, R6, #1
ADD R2, R5, #0
NOT R1, R3
ADD R1, R1, #1
DIVLOOP ADD R4, R4, #1
AND R2, R2, R0
BRn NEGATIVE
BRp DIVLOOP
BRz ZERO
NEGATIVE ADD R4, R4, #-1
ADD R5, R2, R3
ADD R6, R6, #-1
STR R4, R6, #0   
ZERO BRnzp NEXTCHARACTER
EXPONENTIAL ADD R2, R5, #0   

LDR R5, R5, #0
ADD R6, R6, #1   
ADD R3, R5, #0
ADD R1, R1, R3
OUTEREXPOLOOP ADD R4, R1, #0
INNEREXPOLOOP ADD R3, R3, R3
BRp INNEREXPOLOOP
ADD R2, R2, #-1   
BRp OUTEREXPOLOOP   

ADD R6, R6, #-1   
STR R3, R6, #0

BRnzp NEXTCHARACTER
DONE

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