cppreference.com > C++ I/O > precision precision Syntax:
      #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
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