[TangoTrotFox]

Hahaha, mine:

    mov ah, 2
    mov dl, 7
    int 21
    int 20

Discovering that I could write my own programs with debug.com was earth shaking. Picked up some decade old book on it at Half Price Books (which went well with my decade old machine -- an 80s model IBM with integrated monochrome green screen) and never looked back.

[foldr]

Speaking of embarrassing errors, your comment just sent my pre-coffee self on a brief and fruitless visit to http://debug.com

[ktRolster]

I can smell your program. All that new hardware around me. The smell of dot matrix ink.

[onemoresoop]

Yes! I remember my first experience with a PC in the 80s was with a Robotron 8086 PC. It did emanate a smell and I could hear interesting mechanical sounds from inside. The motherboard was huge and it had a small 14 inch monochrome green monitor on top of it.

[lbruder]

That would emit a beep from the speaker, right? So long ago...

[TangoTrotFox]

None other than beep.com!

[fit2rule]

The first assembly program I wrote and got paid a handsome sum for:

    jmp FFF0

The client was amazed that I'd figured out a way to automate the ctrl-alt-del monkeys that had been hired to reboot everyones machines, for some reason, every night ..

[sedatk]

beep!