Where is the center of the coordinate system on a smartphone?

Question

Unity

touch.position returns vector2 . That's the question on the phone where actually 0? In the center of the screen or in the corner, or on different devices in different ways?

Answer 1

What about googling? Smartphones have nothing to do with it - this is a question of the engine.
answers.unity3d.com/questions/232480/coordinates-o...