Use a laptop as a monitor?

Today I cleaned up my basement and found my old pc there. I want to connect it, but I don't have a monitor, but I have a laptop with a display port. What would happen if I connect it to the laptop?

Your laptop probably only has an HDMI output, so this won't be possible, but of course there are exceptions and your laptop has an input.

Nothing. There's an exit on the laptop.

Nothing would happen there.

As a rule, notebooks have a pure exit.

Nothing at all. The Displayport outputs are not inputs. So you won't get a picture on your laptop screen.

OK.