why dont we write iostream.h? Isn't it a header file..?

Answer 1

yes we use <iostream.h> to

Answer 2

<iostream.h> or <iostream> you can use any of these both are correct but <iostream.h> is generally used for older version so it is advised to use <iostream> and if you want a detailed comparison visit : http://members.gamedev.net/sicrane/articles/iostream.html

Answer 3

but sometimes we use only iostream...?