Object-oriented assembly <FASM>

use16
org 100h ;ew, DOS

include "MACRO\STRUCT.INC"

jmp start

struct Enemy ;new class/object
  hp dd 22
  name db 'Zombie$'
  getName dw Enemy_getName ;You can put functions, variables, whatever you'd like!
  size db 0
ends

Enemy_getName:
  mov ax,bx ;We can assume bx is the instance pointer since function new returns it that way. Register ES may also be a good choice.
  add ax,Enemy.name ;Enemy.name is an offset to the name variable, so add it
  ret

enemy Enemy ;use this as your default instance for copying

start:
  mov ax,enemy ;push the default instance
  mov bx,Enemy.size ;push the STRUCT's .size
  call new

  ;new returns the instance pointer in bx, so do what you need to do with it

  call [bx+Enemy.getName] ;We could just directly get the pointer as well with mov ax,[bx+Enemy.name]
  mov dx,ax ;we'll use a DOS interrupt to print the new enemy's name. mov dx,[bx+Enemy.name] would've been more efficient.
  mov ah,09 ;DOS print-string
  int 21h ;DOS interrupt. I usually don't use them, but it's for demonstration purposes
  ret

new: ;makes a new instance of an object. Could also be used to clone an instance.
        ;ax - Instance/object to copy
        ;bx - Size of class
        ;returns: bx - pointer to instance
        ;This could be modified to use pushes instead of registers, but I made an interrupt that pointed to this function.
  pusha
  mov si,ax ;What to copy
  mov ax,[new_obj_ptr]
  mov di,ax ;Where to paste
  mov cx,bx ;Size of object
  rep movsb ;very easy to copy the object.
  popa

  push ax
  mov ax,[new_obj_ptr]
  push ax
  add ax,bx
  mov [new_obj_ptr],ax
  pop ax
  mov bx,ax
  pop ax
  ret

  new_obj_ptr dw _objects ;This will point to where to copy a new instance

_objects:
;This space is reserved for instances. Do not add anything after this. Optionally define 0s so no other memory is loaded here
times 0x400 db 0 ;allocate 1,024 bytes for instances

define Enemy.hp 0 ;if periods don't work, use underscores
define Enemy.name 4
define Enemy.getName 11
define Enemy.size 13

jmp start

Enemy: ;default instance
  dd 24
  db 'Zombie$'
  dw Enemy_getName

Enemy_getName: ;You can technically put it inside the object, but why calculate the size of that and have to copy it?
  mov ax,bx
  add ax,Enemy.name
  ret

start:
  mov ax,Enemy
  mov bx,Enemy.size
  call new
  ;And you can do what you want with it normally
  ret