c++ - Using long double -

the following c++ program. want store long number such pi on variable trying use long double. when run program displays 3.14159 . how store full floating point number variable?

#include <iostream> using namespace std;  int main() { long double pi; pi = 3.14159265358979323846264338327950288419716939937510; cout << "pi = " << pi << endl; return 0; } 

using stream manipulators, it's easy:

#include <iostream> #include <iomanip>  int main() {      long double pi;     pi = 3.14159265358979323846264338327950288419716939937510l; // l long double literal      std::cout << "pi: " << std::setprecision(20) << pi;   }