DOSSEG
       .MODEL SMALL
       .STACK 200H
       .DATA

calc        db    "***CALCULATOR ***$"
operation    db    "Select an Operation$"
addition    db    "[a] Addition $"
subtraction    db    "[b] Subtraction$"
multiplication    db    "[c] Multiplication$"
division    db    "[d] Division$"
op        db    "Your Operation : $"
op_ans        db    6 dup("$")
newline        db    13,10,"$"
addition_wel    db    "You have chosen Addition $"
num1_msg    db    "Input First Number : $"
input_num1    db    10 dup("$")
num2_msg    db    "Input Second Number : $"
input_num2    db    10 dup("$")
sum_msg        db    "The Sum is : $"
sum        db    10 dup("$")
subtraction_wel db    "You have chosen Subtraction $"
difference_msg  db    "The Difference is : $"
difference     db    10 dup("$")
continue    db    "Would you like to continue?[y/n] : "
cont_ans    db    10 dup("$")
sub_num1    db    10 dup("$")
sub_num2    db    10 dup("$")
mul_wel        db    "You have chosen Multiplication $"

.code

clrscr    proc
    push ax
    mov al, 03h
    mov ah, 00h
    int 10h
    pop ax
    ret
clrscr    endp

readstr    proc
    push ax
    mov ah, 0ah
    int 21h
    pop ax
    ret
readstr    endp

printstr proc
    push ax
    mov ah, 09h
    int 21h
    pop ax
    ret
printstr endp


begin: mov ax, @data
       mov ds, ax
       mov es, ax
    
    call clrscr

lbl1:    lea dx,[calc]
    call printstr  

    lea dx, newline
    call printstr

    lea dx,[operation]
    call printstr

    lea dx, newline
    call printstr

    lea dx,[addition]
    call printstr

    lea dx, newline
    call printstr
    
    lea dx,[subtraction]
    call printstr

    lea dx, newline
    call printstr

    lea dx,[multiplication]
    call printstr

    lea dx, newline
    call printstr

    lea dx,[division]
    call printstr

    lea dx, newline
    call printstr
    
    lea dx,op
    call printstr
    
    mov al,op_ans[02]
    mov ah,0ah
    int 21h
    cmp op_ans,"a"
    je lbladdition
    


lbladdition:
    
    lea dx, newline
    call printstr
    
    lea dx, [addition_wel]
    call printstr

    lea dx, newline
    call printstr

    lea dx, [num1_msg]
    call printstr
    
    lea dx, input_num1  ;----->take 1st number input
    mov ah,0ah
    int 21h
    
    mov ah,input_num1[02]
    mov al,input_num1[03]
    sub ax,3030h
    mov bl,al  ;< --- x9
    mov bh,ah  ;< --- 9x
    
    
    lea dx, newline
    call printstr

    lea dx,[num2_msg]
    call printstr
    
    lea dx,input_num2; takes 2nd number input
    mov ah,0ah
    int 21h
    mov ah, input_num2[02]
    mov al, input_num2[03]
    sub ax,3030h
    aad
    mov ch,al
    add ch,bl
    mov al,ch
    aam
    add ax,3030h
    mov bl,ah
    sub bh,30h
    add bh,bl
    add bh,30h
    

    mov sum[0002],bh
    mov sum[0003],al
    mov sum[0005],'$'

    lea dx, newline
    call printstr

    lea dx,[sum_msg]
    call printstr

    lea dx, sum[0002]
    call printstr

    lea dx, newline
    call printstr
    
    
    

lblsubtraction:;-------------------------------> my subtraction doesn't work

    
    lea dx, newline
    call printstr
    
    lea dx, [subtraction_wel]
    call printstr

    lea dx, newline
    call printstr

    lea dx, [num1_msg]
    call printstr
    
    lea dx, input_num1
    mov ah,0ah
    int 21h
    mov ah,input_num1[02]
    mov al,input_num2[03]
    sub ax,3030h
    mov bh,ah
    mov bl,al

    lea dx, newline
    call printstr
    
    lea dx,[num2_msg]
    call printstr

    lea dx,input_num2
    mov ah,0ah
    int 21h
    mov ah,input_num2[0002]
    mov al,input_num2[0003]
    sub ax,3030h
    aad
    mov ch,al
    sub ch,bl
    mov al,bl
    aam
    add ax,3030h
    mov bl,ah
    sub bh,30h
    sub bh,bl
    add bh,30h

    mov difference[0002],bh
    mov difference[0003],al
    mov difference[0005],'$'

    lea dx,[newline]
    call printstr

    lea dx,[difference_msg]
    call printstr

    lea dx,difference[0002]
    call printstr
    
        
    


    
mov ah, 4ch
int 21h

end begin