一个标准库名字空间 The std namespace The ANSI/ISO C++ standard requires you to explicitly declare the namespace in the standard library. For example, when using iostream.h, you do not have to specify the namespace of cout in one of the following ways: std::cout (explicitly) using std::cout (using declaration) using namespace std (using directive) Visual C++ continues to support the use of older header filenames with the .h extension. Such usage does not require invocation of the std namespace described above.
The std namespace
The ANSI/ISO C++ standard requires you to explicitly declare the namespace in the standard library. For example, when using iostream.h, you do not have to specify the namespace of cout in one of the following ways: std::cout (explicitly)
using std::cout (using declaration)
using namespace std (using directive)
Visual C++ continues to support the use of older header filenames with the .h extension. Such usage does not require invocation of the std namespace described above.
例如stdin就是标准输入
stdout就是标准输出的意思~:)
namespace std{
};