What is the difference between iostream and iostream.h in C + +? __c++

#include <iostream.h> non-standard input output stream,

#include <iostream> is a standard input-output stream

In C + + to avoid the name of the conflict, specifically introduced the "namespace definition", namely namespace

When the code is in <iostream.h>, the output can refer directly to cout<<x; <iostream.h> inherits the standard library files of C language and does not introduce namespace definitions, so it can be used directly.

When <iostream> is introduced into the code, STD is introduced;

1,

using namespace Std;

cout<<x;

2,

Using Std::cout;

cout<<x;

3, std::cout<<x;