Addition, Subtraction & Multiplication in .ASM

Addition, Subtraction & Multiplication of two numbers submitted, until the program terminates by user. The termination process is actually maintained by 0 and 1, 0 terminates the program and 1 continues.
Limitations of the code is the initial two numbers and the resultant numbers must be between 0 to 9. "emu8086" compiler was used. This is my 5th code in assembly language I have done in my lab.

; Date: October 10, 2012
; Author: Md. Nabid Imteaj
; Tag: Add, Substract, Multiplication as user want

TITLE ANOTHER_DAY_IN_CLASS  
.model small
.stack 100h
.code

.data
msg1 db 'ENTER Hex Value: $'
msg2 db 'Equivalent Decimal: $' 
msg3 db 'INVALID :($'
msg10 db '0 to exit, 1 to continue?: $'
msg11 db 'THANK YOU :D$' 

main proc
    
    mov ax, @data
    mov ds, ax 
    
    mov cx, 3

AGAIN_PAIN: 
; new line
    mov ah, 2
    mov dl, 0dh
    int 21h
    mov dl, 0ah
    int 21h 

cmp cl, 0
je TERMINATE
dec cx

; message print

    lea dx, msg1
    mov ah, 9
    int 21h
    
; enter character
    mov ah, 1
    int 21h 
    mov bl, al
    
    ; new line
    mov ah, 2
    mov dl, 0dh
    int 21h
    mov dl, 0ah
    int 21h
    
; cmpareing
    cmp bl, 'A'
    je print_A
    cmp bl, 'B'
    je print_B 
    cmp bl, 'C'
    je print_C
    cmp bl, 'D'
    je print_D
    cmp bl, 'E'
    je print_E
    cmp bl, 'F'
    je print_F 
    
    cmp bl, 30
    jge over_0
    
over_0:
    cmp bl, 39
    jle less_9 
    jmp print_invalid

less_9:
    mov ah, 2
    mov dl, bl
    int 21h 
    jmp EXIT_ 
    
print_A:  
lea dx, msg2
mov ah, 9
int 21h
   
    mov ah, 2
    mov dl, '1'
    int 21h
    mov ah, 2
    mov dl, '0'
    int 21h 
    jmp EXIT_ 
    
print_B:
lea dx, msg2
mov ah, 9
int 21h 
    mov ah, 2
    mov dl, '1'
    int 21h
    mov ah, 2
    mov dl, '1'
    int 21h 
    jmp EXIT_
    
print_C:
lea dx, msg2
mov ah, 9
int 21h 
    mov ah, 2
    mov dl, '1'
    int 21h 
    mov ah, 2
    mov dl, '2'
    int 21h 
    jmp EXIT_
    
print_D:
lea dx, msg2
mov ah, 9
int 21h 
    mov ah, 2
    mov dl, '1'
    int 21h 
    mov ah, 2
    mov dl, '3'
    int 21h 
    jmp EXIT_
    
print_E:
lea dx, msg2
mov ah, 9
int 21h 
    mov ah, 2
    mov dl, '1'
    int 21h
    mov ah, 2
    mov dl, '4'
    int 21h  
    jmp EXIT_     
    
print_F:
lea dx, msg2
mov ah, 9
int 21h 
    mov ah, 2
    mov dl, '1'
    int 21h
    mov ah, 2
    mov dl, '5'
    int 21h  
    jmp EXIT_ 
           
print_invalid:
    lea dx, msg3
    mov ah, 9
    int 21h
    jmp EXIT_
               
  
EXIT_: 

; new line
    mov ah, 2
    mov dl, 0dh
    int 21h
    mov dl, 0ah
    int 21h    
    
; operation message
    lea dx, msg10
    mov ah, 9
    int 21h 
    
; gets character
    mov bl, '1'
    mov ah, 1
    int 21h
    
    cmp al, bl
    je AGAIN_PAIN
    
    ; new line
    mov ah, 2
    mov dl, 0dh
    int 21h
    mov dl, 0ah
    int 21h 
    
TERMINATE:   
     ; operation message
    lea dx, msg11
    mov ah, 9
    int 21h 

mov ah, 4ch
int 21h
main endp
end main

Message Print in Assembly Language

TITLE PRINTING HABIJABI

.MODEL SMALL    

.STACK 100H   

.DATA
MSG  DB 'Take Input: $'
MSG1 DB 'First Value: $'
MSG2 DB 'Second Value: $'
A    DB 5
B    DB ?

MAIN PROC
; initializing data segment  
    MOV AX, @DATA
    MOV DS, AX  ; initialized :D 
    
; display message
    LEA DX, MSG
    MOV AH, 9  ; message print function
    INT 21h  
    
; input 
    MOV AH, 1
    INT 21h
    MOV B, AL
    
; new line
    MOV AH, 2
    MOV DL, 0DH
    INT 21H
    MOV DL, 0AH
    INT 21H   
    
; display message1
    LEA DX, MSG1
    MOV AH, 9  ; message print function
    INT 21h
    
; display A
    MOV AH, 2
    MOV DL, A
    INT 21h
    
; new line
    MOV AH, 2
    MOV DL, 0DH
    INT 21H
    MOV DL, 0AH
    INT 21H   
    
; display message2
    LEA DX, MSG2
    MOV AH, 9  ; message print function
    INT 21h
    
; display B 
    MOV AH, 2
    MOV DL, B
    INT 21h
    
; return to DOS

    MOV AH, 4CH
    INT 21h
    
MAIN ENDP
    END MAIN