#include <fstream>
  streamsize precision();
  streamsize precision( streamsize p );

The precision() function either sets or returns the current number of digits that is displayed for floating-point variables.

For example, the following code sets the precision of the cout stream to 5:

   float num = 314.15926535;
   cout.precision( 5 );
   cout << num;           

This code displays the following output:

   314.16