What requires me to declare “using namespace std;”?

Question

This question may be a duplicate, but I can\'t find a good answer. Short and simple, what requires me to declare

using namespace std;

in C+

Answer 1

You never have to declare using namespace std; using it is is bad practice and you should use std:: if you don't want to type std:: always you could do something like this in some cases:

using std::cout;

By using std:: you can also tell which part of your program uses the standard library and which doesn't. Which is even more important that there might be conflicts with other functions which get included.

Rgds Layne