Show Lecture.UsingNamespaceStd as a slide show.
#include <iostream>
allows you to use
symbols such as cin
and cout
.
#include <iostream> using namespace std; int main() { cout << 1/8.1; return 0; }
0.123457
std::cin
and std::cout
.
using namespace std;
#include <iostream> int main() { cout << 1/8.1; return 0; }
c.cc:4: error: 'cout' was not declared in this scope
#include <iostream> int main() { std::cout << 1/8.1; return 0; }
0.123457
cout
, endl
, exit
) go into
the std::
namespace.
main
, global vars) go into the global namespace.
#include <iostream> constexpr auto pi = 3.14159; void cout() { std::cout << "π=" << ::pi << std::endl; } int main() { ::cout(); return 0; }
π=3.14159