DEBUG.COM Hello World - Commented

HELLO.ASM

; This can be run with DEBUG.COM: Run DEBUG.COM < HELLO.ASM. 
; You'll get a HELLO.COM output that outputs "Hello world!"
; This was sourced from http://www2.latech.edu/~acm/helloworld/dosdebug.html, comments are mine.
; Switch to DEBUG.COM assemble mode:
a
mov ah,9    ; 0100 : Put 9 (output to stdout) to ah
mov dx,108  ; 0102 : put 0108 in dx (which should contain the string "Hello world!$" )
int 21	    ; 0105 : Kick the MS-DOS API, which reads from ah
ret	    ; 0107 : Return from procedure
; 0108: Our data:
db "Hello world!$"
; 0115 : Get out of assemble entry mode with the following empty line:

; Write 15 (number of bytes to write to disk) to register cx:
r cx
15
; Set the output filename:
n hello.com
; Write the assembled program:
w
; Quit DEBUG.COM:
q

Comments in this are weird. A couple rules I found:

• Debug.com extensions (in this case, db "Hello world!$") cannot have inline comments - the comment will be interpreted as part of the byte sequence.
• Debug.com commands (those executed outside of assemble mode) also cannot have inline comments