Hello world Assembly x86-16 (MS-DOS, Tiny Memory Model)

; Hello world program
; Language: x86 (16-bit) Assembly (Tiny Memory Model)
; Library: MS-DOS interrupts

org 0x100

section .text
    mov dx, message
    mov ah, 0x9
    int 0x21
    mov ax, 0x4C00
    int 0x21

section .data
    message db 'Hello world!', 0xD, 0xA, '$'