TPad::GetWNDC() and TPad::GetHNDC()

The description of TPad::GetWNDC() and TPad::GetHNDC() lacks any description whatsoever.

What does NDC stand for?

NDC = Normalized Coordinates
See 11.3.2 on https://root.cern.ch/root/html/guides/users-guide/Graphics.html

Description added. Thanks