Reference :- Name Space Tutorial

Namespaces allow to group entities like classes, objects and functions under a name. This way the global scope can be divided in "sub-scopes", each one with its own name.

Important points to remember.

1) Why is "using namespace std;" BAD ?

Well What I can gather from the information given in the article is

See this example
// using
#include
using namespace std;

namespace first
{
int cout = 5;
int y = 10;
}

namespace second
{
double x = 3.1416;
double y = 2.7183;
}

int main () {
using namespace first;
// using namespace second;
std::cout << cout; --> // Error. But if we dont use using namespace std; This code will run

return 0;
}

Here we have two namespaces defined and now we have ambiguous variables. Removing ambiguity was the main reason for using namespaces right ;)

So its better not to use using globally but rather than use it for what you require.
Nevertheless its not such a big issue in my opinion

Labels: C++, Namespace