For LC-3 I need to ask the user to input two numbers and add them, then print ou

Question

For LC-3 I need to ask the user to input two numbers and add them, then print out the sum. Can you tell me where I need to put the code to add and how to do it. Is it ADD R2,R1,R0?

; This program echoes a user's input.

; The code will begin in memory at the address
; specified by .orig .

   .ORIG   x3000

START:
; clear all registers that we may use
   AND   R0, R0, 0
   AND   R1, R0, 0
   AND   R2, R0, 0
   AND   R3, R0, 0
   AND   R4, R0, 0
   AND   R5, R0, 0
   AND    R6, R0, 0
   AND   R7, R0, 0

; print out a greeting
   LEA   R0, GREETING1
   PUTS

; get a user-entered character (result in R0)
; echo it back right away (otherwise it isn't visible)
   GETC
   PUTC

; store entered string (otherwise it may be overwritten)
   ST   R0, USERINPUT

; print out a newline and some other stuff
   LEA   R0, NEWLINE1
   PUTS

; print out the user's input
   LD   R0, USERINPUT
   PUTC

; print out the rest of the sentance
   LEA   R0, USERSTRING1
   PUTS

; print out a greeting
   LEA   R1, GREETING2
   PUTS

; get a user-entered character (result in R1)
; echo it back right away (otherwise it isn't visible)
   GETC
   PUTC

; store entered string (otherwise it may be overwritten)
   ST   R1, USERINPUT

; print out a newline and some other stuff
   LEA   R1, NEWLINE2
   PUTS

; print out the user's input
   LD   R1, USERINPUT
   PUTC

; print out the rest of the sentance
   LEA   R1, USERSTRING2
   PUTS

;ADD
    ADD   R2,R1,R0
   PUTS

; echo it back right away (otherwise it isn't visible)
   GETC
   PUTC

; stop the processor
   HALT

; data declarations follow below

; strings
GREETING1:   .STRINGZ   "Welcome to the sample program. Please Enter the first number: "
USERSTRING1:   .STRINGZ   " <-- is the character you entered. "
NEWLINE1:   .STRINGZ    " --> ";
GREETING2:     .STRINGZ       "Enter the second number. "
USERSTRING2:   .STRINGZ   " <-- is the character you entered. "
NEWLINE2:   .STRINGZ    " --> ";
; variables
USERINPUT:   .FILL   0

; end of code
   .END

Explanation / Answer

.model small .stack 100h .data prompt db 13, 10, 'First number:','$' prompt db 13,10, 'Second number:', '$' result db 13, 10, 'Sum','$' ;Variables num1 db ? num2 db ? sum db ? .code main proc mov ax,@data ;get data segment address mov ds,ax ;initialize ds ;Display Prompt mov ah,9 ;print string function mov dx,offset prompt ;ds:dx points to string int 21h mov ah,1 ;input function int 21h xor ah,ah ;clear the top 8 bits of ax mov num1, ax ;save the value from input mov ah,9 lea dx, prompt2 ;print prompt int 21h mov ah,2 ;input second function int 21h xor ah, ah ;clear the top 8 bits of ax mov num2, ax ;save the value from second input ;Addition mov ax,num1 ;move num1 into ax add ax,num2 ;add first and second numbers together mov sum,ax ;move the total sum of numbers in sum ;Print Sum mov ah,9 lea dx, result ; print result int 21h mov ah,2 mov dl,bl int 21h mov dl,'+' ;display + sign int 21h mov dl,bh int 21h mov dl,'=' ;display = sign int 21h mov dl,bh int 21h mov ah,4ch int 21h main endp end main

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