org 100h

EntryPoint:
        push Arr1 Arr2 Size
        cmp ax, 0
        call MyProc
        ret

MyProc:
        push    bp
        mov     bp, sp
        push    si di
        mov     cx, [bp + 4]

        mov     si, [bp + 8]
        mov     di, [bp + 6]
        repe   cmpsb
        jz .Case0
        mov     ax, [bp + 4]
        sub     ax, cx
        jmp .EndProc
.Case0:
        xor ax, ax
.EndProc:
        pop     di si bp
        ret     6


Arr1    db 3, 2, 1
Arr2    db 3, 2, 1
Size = 3