Namespaces

For names that are brought in by standard includes like cout, there are 3 things that may be done:

1. Prefix the NAME with std::.

2. Use using std::NAME before the name is used.

3. Put using namespace::std before the name is used.

Do NOT use options 2 or 3. You may see it used, even in text books, but it is bad programming practice.

Examples

These examples use cout for NAME:

1. Prefix the NAME with std::

   // Best practice

   int main()

   {

       std::cout << "Hello World!\n";

       // ...

2. Use using std::NAME before the name is used

   // File scope, avoid this one

   //using std::cout;

   int main()

   {

       // Block scope

       using std::cout;

       cout << "Hello World!\n";

       // ...

3. Put using namespace::std before the name is used.

   // Do NOT use this

   using namespace std;

   int main()

   {

       cout << "Hello World!\n";

       // ...