About iostream and C + + namespaces

C + + standard library functions are in the STD namespace, want to use must add using namespace std, here are a few ways to use

1. Specify the identifier directily, for example Std::ostream instead of ostream. The complete sentence is as follows:

std:: cout << std:: hex << 3.4 << std:: endl;

2. Using the "suing" key word

Using std:: cout;
Using std:: Endl;
The above code can be written as
cout << std:: hex << 3.4 << Endl;

3. The most convenient are to useing namespace std

All identifier defined in namespace STD is valid, as if they were declared as global varibales. Then the above statement can is written as follows:

cout << "I didn ' t pass the CET four" << "Ma mai Pi";

About iostream and C + + namespaces