Precision of double: setprecision : double output « Data Types « C++ Tutorial

1. C++ Tutorial
2. Data Types
3. double output

#include <iomanip>
#include <iostream>

using namespace std;

int main( ){
   const double x = .39;
   const double y = 27;

   cout<< ".39, fixed, 1 decimal place:  "
      << fixed << setprecision( 1 ) << x << endl

      << ".39, fixed, 2 decimal places: "
      << setprecision( 2 ) << x << endl

      << ".39, fixed, 3 decimal places: "
      << setprecision( 3 ) << x << endl << endl

      << ".39, scientific, 1 decimal place:  "
      << scientific << setprecision( 1 ) << x << endl

      << ".39, scientific, 2 decimal places: "
      << setprecision( 2 ) << x << endl

      << ".39, scientific, 3 decimal places: "
      << setprecision( 3 ) << x << endl << endl

      // return to default floating-point output format
      << resetiosflags( ios::fixed | ios::scientific )
      << setprecision( 6 )

      << ".39 and 27., default: "  << x << "    " << y << endl

      << ".39 and 27., default, 1 decimal place:  "
      << setprecision( 1 ) << x << "    " << y << endl

      << ".39 and 27., default, 2 decimal places: "
      << setprecision( 2 ) << x << "    " << y << endl

      << ".39 and 27., default, 3 decimal places: "
      << setprecision( 3 ) << x << "    " << y << endl << endl

      << ".39 and 27., default, decimal point: "
      << showpoint << x << "   " << y << endl

      << ".39 and 27., default, decimal point, 1 decimal place:  "
      << setprecision( 1 ) << x << "    " << y << endl

      << ".39 and 27., default, decimal point, 2 decimal places: "
      << setprecision( 2 ) << x << "    " << y << endl

      << ".39 and 27., default, decimal point, 3 decimal places: "
      << setprecision( 3 ) << x << "   " << y << endl;
}