Калькулятор для десятичных чисел. При выводе чисел >9 искажает их.

ection .data
 
msg1 db "-Calculator-", 0x0a 
lmsg1 equ $-msg1
 
msg2 db "Number 1: ", 0x0a
lmsg2 equ $-msg2
 
msg3 db "Number 2: ", 0x0a
lmsg3 equ $-msg3
 
msg4 db "1. Add", 0x0a
lmsg4 equ $-msg4
 
msg5 db "2. Subtrat ", 0x0a
lmsg5 equ $-msg5
 
msg6 db "3. Multiply", 0x0a
lmsg6 equ $-msg6
 
msg7 db "4. Divide", 0x0a
lmsg7 equ $-msg7
 
msg8 db "Operation: ", 0x0a
lmsg8 equ $-msg8
 
msg9 db "Result", 0x0a
lmsg9 equ $-msg9
 
msg10 db "Invalidm Option", 0x0a
lmsg10 equ $-msg10
 
nlinea db 10,10,0
lnlinea equ $-nlinea
 
 
 
section .bss
 
opc resb 2
num1 resd 1
num2 resd 1
result resb 2
 
 
section .text
global _start
 
_start:
mov eax,4
mov ebx,1
mov ecx, msg1
mov edx, lmsg1
int 80h
 
mov eax, 4
mov ebx, 1
mov ecx, msg2
mov edx, lmsg2
int 80h
 
mov eax, 3
mov ebx, 0
mov ecx, num1
mov edx, 4
int 80h
 
mov eax, 4
mov ebx, 1
mov ecx, msg3
mov edx, lmsg3
int 80h
 
mov eax, 3
mov ebx, 0
mov ecx, num2
mov edx, 4
int 80h
 
mov eax, 4
mov ebx, 1
mov ecx, msg4
mov edx, lmsg4
int 80h
 
mov eax, 4
mov ebx, 1
mov ecx, msg5
mov edx, lmsg5
int 80h
 
mov eax, 4
mov ebx, 1
mov ecx, msg6
mov edx, lmsg6
int 80h
 
mov eax, 4
mov ebx, 1
mov ecx, msg7
mov edx, lmsg7
int 80h
 
mov eax, 4
mov ebx, 1
mov ecx, msg8
mov edx, lmsg8
int 80h
 
mov eax, 3
mov ebx, 0
mov ecx, opc
mov edx, 4
int 80h
 
mov ah, [opc]
sub ah, '0'
 
;vibor---------<
cmp ah, 1
je add
cmp ah, 2
je subtract
cmp ah, 3
je multiply
cmp ah, 4
je divide
 
mov eax, 4
mov ebx, 1
mov ecx, msg10
mov edx, lmsg10
int 80h
 
jmp exit
 
;---------------------<
add:
 
mov eax, dword [num1]
 
mov ebx, dword [num2]
 
sub eax, '0'
sub ebx, '0'
 
add eax, ebx
 
add eax, '0'
 
mov [result], eax
;mov edx,eax
mov eax, 4
mov ebx, 1
mov ecx, msg9
mov edx, lmsg9
int 80h
 
mov eax, 4
mov ebx, 1
mov ecx, result
mov edx, 2
int 80h
;syscall
 
jmp exit
 
subtract:
 
mov eax, [num1] 
mov ebx, [num2]
 
sub eax, '0'
sub ebx, '0'
 
sub eax,ebx
 
add eax, '0'
 
mov [result],eax
 
mov eax, 4
mov ebx, 1
mov ecx, msg9
mov edx, lmsg9
int 80h
 
mov eax, 4
mov ebx, 1
mov ecx, result
mov edx, 1
int 80h
 
jmp exit
 
multiply:
 
mov eax, [num1]
mov ebx, [num2]
 
sub eax, '0'
sub ebx, '0'
 
mul ebx
 
add eax, '0'
 
mov [result], eax
 
mov eax, 4
mov ebx, 1
mov ecx, msg9
mov edx, lmsg9
int 80h
 
mov eax, 4
mov ebx, 1
mov ecx, result
mov edx, 1
int 80h
 
jmp exit
 
divide:
 
mov al, [num1]
mov bl, [num2]
 
mov dx, 0
mov ah, 0
 
sub al, '0'
sub bl, '0'
 
div bl
 
add ax, '0'
mov [result], ax
 
mov eax, 4
mov ebx, 1
mov ecx, msg9
mov edx, lmsg9
int 80h
 
 
mov eax, 4
mov ebx, 1
mov ecx, result
mov edx, 1
int 80h
 
jmp exit
 
exit:
 
mov eax, 4
mov ebx, 1
mov ecx, nlinea
mov edx, lnlinea
int 80h
 
mov eax, 1
xor ebx, 0
int 80h