// This test scoring program does not accept test scores
// that are less than 0 or greater than 100.
#include <iostream>
using namespace std;

int main()
{
   // Constants for grade thresholds
   const int A_SCORE = 90,
             B_SCORE = 80,
             C_SCORE = 70,
             D_SCORE = 60,
             MIN_SCORE = 0,    // Minimum valid score
             MAX_SCORE = 100;  // Maximum valid score

   int testScore;  // To hold a numeric test score

   // Get the numeric test score.
   cout << "Enter your numeric test score and I will\n"
        << "tell you the letter grade you earned: ";
   cin >> testScore;

   // Validate the input and determine the grade.
   if (testScore >= MIN_SCORE && testScore <= MAX_SCORE)
   {
      // Determine the letter grade.
      if (testScore >= A_SCORE)
        cout << "Your grade is A.\n";
      else if (testScore >= B_SCORE)
        cout << "Your grade is B.\n";
      else if (testScore >= C_SCORE)
        cout << "Your grade is C.\n";
      else if (testScore >= D_SCORE)
        cout << "Your grade is D.\n";
      else
        cout << "Your grade is F.\n";
   }
   else
   {
      // An invalid score was entered.
      cout << "That is an invalid score. Run the program\n"
           << "again and enter a value in the range of\n"
           << MIN_SCORE << " through " << MAX_SCORE << ".\n";
   }

   return 0;
}