Namespace STD Reference <iostream> when used

The so-called namespace refers to the various visible ranges of identifiers. All identifiers in the C + + standard library are defined in a namespace named Std, so that all identifiers defined within the namespace Std are valid. Why put cout in Std, because the user will use cout and so on multiple times, to prevent this object is used multiple times. <iostream> and <iostream.h> are not the same, the former has no suffix, the two are two files, inside the code is not the same. <iostream.h> has not been used. 1, using namespace std;2, std::cout<<

Namespace STD Reference <iostream> when used