Addition in emu8086 class CSE231 Lab

.MODEL SMALL
.STACK 100H
.DATA
MSG DB   " Addition of 3 numbers$"

PROMPT1 DB 10,10,13,"ENTER A FIRST NUMBER:$"
PROMPT2 DB 10,13,"ENTER A SECOND NUMBER:$"
PROMPT3 DB 10,13,"ENTER A 3rd NUMBER:$"
PROMPT4 DB 10,10,13,"ANSWER:$"
NUM1    DB ?,'$'
NUM2    DB ?,'$'
NUM3    DB ?,'$'
.CODE
MAIN PROC

    MOV AX,@DATA
    MOV DS,AX
    INT 21H

    MOV AH,9
    MOV DX,OFFSET MSG
    INT 21H

    MOV AH,9
    MOV DX,OFFSET PROMPT1
    INT 21H

    MOV AH,1
    INT 21H
    SUB AL,30H
    MOV NUM1,AL

    MOV AH,9
    MOV DX,OFFSET PROMPT2
    INT 21H

    MOV AH,1
    INT 21H
    SUB AL,30H
    MOV NUM2,AL




    MOV AH,9
    MOV DX,OFFSET PROMPT3
    INT 21H


    MOV AH,1
    INT 21H
    SUB AL,30H
    MOV NUM3,AL

    MOV AH,9
    MOV DX,OFFSET PROMPT4
    INT 21H


    MOV AL,NUM1
    ADD AL,NUM2
    ADD AL,NUM3
    ADD AL,30H

    MOV AH,2
    MOV DL,AL
    INT 21H

    MOV AH,4CH
    INT 21H
ENDP
END MAIN