Subtraction assembly with “base 10” EMU8086

Question

Hello I'm making a base 10 calculator in assembler that can take number with max length of 5 dig... so there is two numbers after the input was taken one of the five dig number is stored in ax and bl for example

AX - 23 45
BX - 00 01

So the value of the input is 12345 And the other is for example is 23243 and it's stored on CX and DX with the same idea of the first number (that stored in AX and BX ...) Now, I have made the addition code, but I can't figure out how making the Subtraction code with all the neg problem...

So what I thought to do is to, for example, take bh (that I'm not using because the number can't be longer than 6 digs...) and if the number is negative Ill put 1 and if its positive I'll put 0 so this problem is solved, Now the problem is that I dont know how to make the code work like with all the sub part and the carry and every thing ...(in the addition i used commands like adc,daa...)

last example: value is: 12345 and its positive

AX - 23 45  
BX - 00 01 
(if Bh is 0 the number is positive if 1 its negative...)

Now the value is : 23243 and its positive CX - 32 43 DX - 00 02

Calculation 12345-23243(= -10898)

lets say the answer goes to CX AND DX so it will look like that:

CX - 08 98
DX - 01 01

answer: (-10898)

Can someone please help me/give me an example code that I'll know how to do it ?

Sorry if I'm little bit Confused...

Thx. EDIT: here is the addition code that you ask for:

proc Add_two_numbers;2 values useing stack...
    pop [150]
    pop dx
    pop cx
    pop bx
    pop ax
    add al,cl
    daa 
    mov cl,al
    mov al,ah
    adc al,ch
    daa
    mov ch,al
    mov al,bl
    adc al,dl
    daa
    mov dl,al
    push cx
    push dx
    push [150]
    ret
endp Add_two_numbers  

2nd edit: I figure out how making it Negative so I just need algorithms that sub 2 number it does not need to work with numbers like 1000-2000 please make it work only on positive values like 2000-1000

Answer 1

Answering your comment, this is one way you can convert from decimal and back using C as an example. I leave you to code it in asm!

#include <conio.h>

#define MAX  100000000

// input a signed decimal number
int inp_num(void) {
    int number=0, neg=0, key;
    while (number < MAX) {
        key = _getche();
        if (key == '-') {
            if (number==0)
                neg = 1;        // else ignore
        }
        else if (key >= '0' && key <= '9')
            number = number * 10 + key - '0';
        else
            break;
    }
    if (neg)
        number = -number;
    _putch('\n');
    return number;
}

// output a signed number as decimal
void out_num(int number) {
    int digit, suppress0, d;
    suppress0 = 1;              // zero-suppression on
    if (number < 0) {
        _putch('-');
        number =-number;
    }
    for (d=MAX; d>0; d/=10) {
        digit = number / d;
        if (digit)              // if non-0
            suppress0 = 0;      // cancel zero-suppression
        if (!suppress0)
            _putch('0' + digit);
        number -= digit * d;
    }    
}

int main(void) { 
    int number;
    number = inp_num();
    out_num(number);
    return 0;
}