.model small ; small memory model (64 KB)
.stack 100h ; reserve 100h bytes for stack
.data
    message db 'HELLO WORLD', 13, 10, '$' ; 13 = \r, 10 = \n, string must be terminated with $
.code
start:
    mov ax, @data ; unable to put in ds directly 
    mov ds, ax
    mov dx, offset message ; offset of the message (0)
    mov ah, 09h ; display string ds:dx
    int 21h ; main system interrupt
    
    mov al, 0 ; return code 0
    mov ah, 4Ch ; terminate with return code
    int 21h
end start