Percent grades. (arrays)

//Christian Ballard
//COSC 1330 - 003
//This program should calculate and dislplay a student's letter grade.
#include <iostream>
#include <iomanip>
using namespace std;

int main()
{
    char letterGrades[5] = { 'A', 'B', 'C', 'D','F' };//Inputs!!!
    int letterGradeNumbers[5] = { 90, 80, 70, 60, 0 };
    double possiblePoints = 0.0;
    double pointsRecieved = 0.0;
    double percentGrade = 0.0;
    char updateRead = ' ';
    cout << fixed << setprecision(1);//I decided to show the percent grade and didn't want the decimal to run on.

    do//The loop that loops the entire program.
    {
        system("cls");//Clearing the screen.
        cout << "Please enter how many points are possible to recieve." << endl;//Getting some inputs.
        cin >> possiblePoints;
        cout << "How many points did you recieve?" << endl;
        cin >> pointsRecieved;

        percentGrade = (pointsRecieved / possiblePoints) * 100;//Our calculations.

        for (int counter = 0; counter < 5; counter++)//Our second loop that determines the letter grade.
        {
            if (percentGrade >= letterGradeNumbers[counter])//Figuring out what letter to use.
            {
                cout << "Your percent grade is " << percentGrade << endl;//Displays.
                cout << "Your letter grade is " << letterGrades[counter] << endl;
                break;//Breaking us out of the loop.
            }
        }
        updateRead = toupper(updateRead);//Keeping letters uppercase for the update read for the loop.
        cout << "Would you like to calculate another grade? (Y/N)" << endl;//Update read.
        cin >> updateRead;
    } while (updateRead == 'Y'); //End of the loop.
    system("cls");
    if (updateRead = 'N')
        cout << "Goodbye!" << endl;//Exiting.

    system("pause");
    return 0;
}