Sep 20, 2013 · When you make a call to using namespace <some_namespace>; all symbols in that namespace will become visible without adding the namespace prefix. A symbol may be for instance a function, class or a variable. E.g. if you add using namespace std; you can write just cout instead of std::cout when calling the operator cout defined in the namespace std.

This is called a namespace. So you tell the compiler, you want to use cout from the namespace std. With using namespace std; #include <iostream> using namespace std; int main() { cout << "Hello World" << endl; // important line return 0; } There you tell the compiler, to open the std namespace four you in this

The following syntax to do this is as follows: using namespace connection: or in your case. using namespace std; So by doing this with std you will be granting that access to std namespace which includes C++ I/O objects cout and cin to use freely without having to use the namespace and scope operator first.

Dec 16, 2014 · Why should using namespace std; be avoided? Reason 1: To avoid name collision. Because the C++ standard library is large and constantly expanding, namespaces in C++ are used to lessen name collisions. You are importing everything wholesale when you use "using namespace std;". That's why "using namespace std;" will never appear in any ...

Dec 7, 2015 · std::string test = "Test"; inside the global namespace makes perfect sense as-is. The name test is simply introduced, as with any other declaration. No need to look it up anywhere. This would be an entirely different kettle of fish: namespace X { struct C { static std::string test; }; } using namespace X; std::string C::test = "Test";

Excluding the basics (Having to add std:: infront of all stl objects/functions and less chance of conflict if you don't have 'using namespace std') It is also worth noting that you should never put . using namespace std In a header file, as it can propagate to all files that include that header file, even if they don't want to use that namespace.

May 23, 2014 · Or, if you want to always use a specific namespace, you can do this: using namespace MyNamespace; MyClass* pClass = new MyClass(); Edit: Following what bernhardrusch has said, I tend not to use the "using namespace x" syntax at all, I usually explicitly specify the namespace when instantiating my objects (i.e. the first example I showed).

The ancient TurboC++ compiler does not follow the standard, so its standard library just puts names in the global namespace, so you have to refer to string not std::string and you can't use using-directives. The first C++ standard was published in 1998, so you should not be using pre-standard compilers in 2013, it will not be a valuable education.

May 31, 2012 · It's used whenever you're using something that is declared within a namespace. The C++ standard library is declared within the namespace std. Therefore you have to do. using namespace std; unless you want to specify the namespace when calling functions within another namespace, like so: std::cout << "cout is declared within the namespace std";

May 6, 2021 · So, essentially, without using namespace std; when you try to write cout << value; you have have to put std::cout << value;. By, adding this syntax to your preprocessor, you get free from adding std:: again and again, and also reduces the chances of any syntax error, as the compiler is instructed before the runtime that we are intended to use a ...