What is/are supposed to show up on the screen as soon as you plug in a headphone in the desktop computer?

Nothing. Nothing is supposed to appear.

I use a USB headset and see a message about USB device being set up.

Depends on the operating system and the type of headphone. Generally nothing. Some might give you a little box saying what it thinks you just plugged in, but often headphones give nothing, unless they use a USB cord (most headphones just use an audio plug).

I think that the person who plugged in the headset is supposed to observe that the headset is plugged in, without recourse to the screen.

@Call_Me_Jay, How about the most basic headphones (like from 30 yrs ago or something,but not necessarily). There is supposed to be 3 OKs to click on before hearing sound.

@Zaku “Depends on the operating system and headphone”. Very sound answer. Thank you

@elbanditoroso Hehe. Yes, though computer cases ports may not actually be connected, or there may be some other form of hardware/software problem. Also a computer may have several audio plugs which are not well-labelled, all of which can take an audio plug but not all are headphone ports. Or your OS or software may mis-identify what you plug in. In which cases, it can be handy if the computer can acknowledge what it thinks you have plugged in, or not.

@ZakuThanks again.

Do you think the average lay person would know that audio plug and headphone jack do different things?

@flo There is supposed to be 3 OKs to click on before hearing sound…

Where did you hear that, or read it? I have been around computers since the mid 1990s, and have NEVER seen “3 OKs” to click on.

My computer at work running Windows, and my iMac at home, I can just plug headphones into the headphone jack et voila! Sound!

@flo No, I don’t think so. Also it doesn’t help that many instructions for electronics are extremely poorly translated into English.

@Zaku That’s wat I thought.