heap_size:
  dw 0x0100

heap_init:
  push ax ; byte value (0)
  push cx ; loop counter
  push di ; target ptr
  push es
  mov ax, ds
  mov es, ax
  xor ax, ax
  mov cx, [heap_size]
  mov di, heap
  rep stosb ; rep makes this loop cx times, incrementing di, writing al
  pop es
  pop di
  pop cx
  pop ax
  ret

; in	ax	number of bytes to alloc
; out	ds:di
malloc:
  push dx ; length of block index
  or ax,0x0F
  inc ax
  mov dx, 0x100
  mov bp, heap

  int 0x2E
  pop dx
  ret