Why do different c++ ide have different header files?

Question

like <iostream.h> and <iostream>

Answer 1

as far as I know, post C++03, <iostream.h> had been replaced by <iostream>, this was at least 12-14 years ago.

Answer 2

I think the new version of c++ compiler use <iostream> an old version use <iostream.h>

Answer 3

ls geany and turbo cpp are the only ide's that uses a .h format for header files