HDMI to Displayport question

[Cycotech]

I was wondering if someone had a a hdmi to displayport adapter and they plugged in their game system to the new imac 27 inch to use it as a screen how would it actually start. would you need an app or it would just start automatically when you hit the power button on the game system. i just got my mac for christmas first time user so just wondering.

 

[tomacintosh]

https://forums.macrumors.com/threads/806175/