What is standard namespace?

Answer 1

std is an abbreviation of standard. stdis the standard namespace. cout, cin and a lot of other things are defined in it. ( This means that one way to call them is by using std::cout andstd::cin.) The keyword using technically means, use this whenever you can.

Answer 2

#include<iostream.h>

Answer 3

if std is for cout, cin etc. what is the function of iostream header