first asm

assume cs:codesg

codesg segment

    mov ax,0123H
    mov bx,0456H
    add ax,ax
    add ax,ax
    
    mov ax,4c00H
    int 21H

codesg ends

end

.data

.stack

.code
main proc
   mov cx,3 
   call sub1 
   mov ax, 4c00h ; exit to operating system.
   int 21h
main endp

sub1 proc
    mov ax,1
    call sub2
    ret
sub1 endp    

sub2 proc
    mov bx,2    
    ret
sub2 endp

end main