. . .   
   // If the input file does not exist, this will detect that. 
   // We handle that by printing an error message and stopping the program.
   if ( In.fail() ) {
      cout << "Data file not found: "     // Write an error message...
           << dataFileName                //    including the file name.
           << endl                        // Bang "return"
           << "Exiting now..." << endl;   // Finish the message.
      return 1;                           // Traditional to return 1 on failure.
   }

. . .

   // Now calculate the average score.
   double AverageScore;
   if ( NumberOfPlayers > 0 ) {    // Check to be sure it's safe to divide.

      // We convert the integers to decimal values before dividing:
      AverageScore = double(SumOfScores) / double(NumberOfPlayers);
   }
   else {
      AverageScore = 0.0;
   }