DOSSEG

.MODEL SMALL

.STACK 100h

.DATA

HelloMessage DB 'Chao cac ban!', 13, 10, '$'

.CODE

mov ax, @Data

mov ds, ax

mov ah, 9

mov dx, OFFSET HelloMessage

int 21h

mov ah, 4ch

int 21h

END

Warning: DOSSEG directive ignored in module HELLO.ASM 
Fatal: No program entry point

Start:
...
end Start

STARTPOINT:
...
END STARTPOINT

.CODE
 
 mov ax, @Data
 
 mov ds, ax
 
 mov ah, 9
 
 mov dx, OFFSET HelloMessage
 
 int 21h
 
 mov ah, 4ch
 
 int 21h
 
 END