Class Functions Not Working

I am taking a Data Structures using C++ class. This is my second program for this class, and I just finished 46 programs in my C++ class.

The chapter covered Classes, the basics only.
The program is to convert the roman number into an Arabic (decimal) number.
The progam consists of a class.
That should:
-Store the number as a roman numeral.
-Convert and store the number as a decimal.
-Print the number as a roman or decimal number as requested by the user.
And there are three roman numerals to test the code.

Everything I here compiles, but doesn't give the right result. I only get one roman numeral character to print and the arabic equivalent is the first two characters plus the previous amount.

I have gone cross-eyed looking at this, and can't see what the problem might be.

I would appreciate a few more peepers to take a look.

My "romanType.h" file

Code:

---

#include <string>
using namespace std;

class romanType
{
public:
        romanType();
        //Default Constructor

        romanType(string roman);
        //Constructor

        void storeRomanNumber(string roman);
        //Function to store the roman numeral
        //Checks to see if all characters in the string are valid

        void convertRomanNumber();
        //Function to convert the Roman Number into and equivalent Arabic Number

        void printRomanNumber();
        //Prints the Roman Number as entered by the user

        void printArabicNumber();
        //Prints the converted Arabic equivalent number
       
private:
        int romanToArabic;
        string romanNumeral;
};

---

My romanType.cpp" file - with the function definitions for my class

Code:

---

#include "romanType.h"

romanType::romanType()
{
    romanNumeral = 'O';
    romanToArabic = 0;
}

romanType::romanType(string roman)
{
    storeRomanNumber(roman);
}

void romanType::storeRomanNumber(string roman)
{
        for (int i = 0; i < roman.size(); i++)
                if (islower(roman[i]))
                        roman[i] = toupper(roman[i]);

        for (int i = 0; i < roman.size(); i++)
        {
                if (roman[i] == 'M' ||
                        roman[i] == 'D' ||
                        roman[i] == 'C' ||
                        roman[i] == 'L' ||
                        roman[i] == 'X' ||
                        roman[i] == 'V' ||
                        roman[i] == 'I')
                        romanNumeral[i] = roman[i];
                else
                        romanNumeral[i] = 'N';
        }

}// end storeRomanNumber

void romanType::convertRomanNumber()
{
        int a = 0,
            z = 0,
            minusMaybe = 0;
        for (int i = romanNumeral.size(); i >= 0; i--)
        {
                if (romanNumeral[i] == 'M') z = 1000;
                if (romanNumeral[i] == 'D') z = 500;
                if (romanNumeral[i] == 'C') z = 100;
                if (romanNumeral[i] == 'L') z = 50;
                if (romanNumeral[i] == 'X') z = 10;
                if (romanNumeral[i] == 'V') z = 5;
                if (romanNumeral[i] == 'I') z = 1;

                if (z < a) minusMaybe = -1;
                else minusMaybe = 1;

                romanToArabic = romanToArabic + (z * minusMaybe);
                a = z;
        }// end for
}// end convertRomanNumber

void romanType::printRomanNumber()
{
        cout << romanNumeral << endl;
}

void romanType::printArabicNumber()
{
        cout << romanToArabic << endl;
}

---

and, finally my "romanNumeralMain.cpp" file

Code:

---

#include <iostream>
#include <string>
#include "romanType.h"

using namespace std;

void displayBanner();
void displayQuestion();

int main()
{
        romanType romanNum;

        char userSelection;
        string roman;

        displayBanner();
       
        romanNum.storeRomanNumber("mcxiv");
        romanNum.convertRomanNumber();
        cout << "\nThe Roman numeral: ";
        romanNum.printRomanNumber();
        cout << "is equivalent to: ";
                romanNum.printArabicNumber();
        cout << endl;

        romanNum.storeRomanNumber("ccclix");
        romanNum.convertRomanNumber();
        cout << "\nThe Roman numeral: ";
        romanNum.printRomanNumber();
        cout << "is equivalent to: ";
                romanNum.printArabicNumber();
        cout << endl;

        romanNum.storeRomanNumber("MDCLXVI");
        romanNum.convertRomanNumber();
        cout << "\nThe Roman numeral: ";
        romanNum.printRomanNumber();
        cout << "is equivalent to: ";
                romanNum.printArabicNumber();
        cout << endl;

        displayQuestion();
        cin >> userSelection;

        while (userSelection == 'Y' || userSelection == 'y')
        {
                cout << "\nEnter a Roman numeral: ";
                cin >> roman;
                cout << "\nThe Roman numeral you entered is: ";
                romanNum.printRomanNumber();
                romanNum.storeRomanNumber(roman);
                cout << "\nThe Arabic equivalent of this Roman numeral is: ";
                romanNum.convertRomanNumber();
                romanNum.printArabicNumber();
                cout << endl;

                displayQuestion();
                cin >> userSelection;
        }// end while
}// end main


void displayBanner()
{
        cout << "\nThis program allows you to enter a Roman numeral;"
                << "\nit then converts the string of characters into"
                << "\nthe equivalent Arabic number.\nHere are some examples:";
}

void displayQuestion()
{
        cout << "\nThe Roman to Arabic conversion is:"
                        << "\n\tM = 1000\n\tD = 500\n\tC = 100\n\tL = 50\n\tX = 10\n\tV = 5\n\tI = 1\n"
                        << "\nWould you like to enter a Roman numeral to convert?" << endl;
}

---

Thanks for the help if anyone can!

Thanks ALL!
But, I figured it out.