why we do not use .h after iostream

Answer 1

cuz i believe this is for old compilers or for C/C#
we are dealing with C++ here a new version too

Answer 2

if you don't writes it then also it works

Answer 3

The compiler automatically puts .h if it doesn't exist.

Answer 4

remember, if you want..
#include<iostream>
then always write after
using namespace std;
this line. otherwise, if
you are written..
#include<iostream.h>
then no need above line.
in short, without header
.ext file you must need
that line unless simple it.
thank you.