Class and header file questions

[Jon15]

Hey, is there a way to run this exactly the way it is except without using the (stdlib.h) header file? I am not too familiar with it at all and I had a friend implement it into the code, but I am not sure how it works. I know there are other ways to change a string to an int, I just can't remember them. ( Similar to the way it is used in the 'return' section of the program)

#include <iostream>
#include <stdlib.h>
#include <iomanip>
#include <cmath>
#include <string>
#include <fstream>
using namespace std;

enum UserType{Users, Admin};
const unsigned short Max_Titles = 3, Max_Copies = 2,
                         Max_Users = 4, Access_Code = 2;

class BlueBox
{
    string m_inventory[Max_Titles][Max_Copies];
    string m_users[Max_Users][Access_Code];
	 int m_revenue;

	const unsigned short customer(const unsigned int) ;
    void rent(const unsigned int);
    void returns();
    void sales(const string&);
    void admin() const;
    void error(const string& message){system("CLS"); cout << message << endl; exit(0);}
public:
    BlueBox(const string inventory[][Max_Copies], const string users[][Access_Code]);
    void screen();
};

int main()
{
    const string Inventory[][Max_Copies] = {{"Star Wars", "2"},
                                            {"Avengers", "2"},
                                            {"Halloween", "2"}};
    const string Users[][Access_Code] = {{"Guest1", "00"},
                                         {"Guest2", "01"},
                                         {"Guest3", "12"},
                                         {"Admin", "99"}};

    BlueBox dvdStore(Inventory, Users);

    dvdStore.screen();

    return 0;
}

BlueBox::BlueBox(const string inventory[][Max_Copies], const string users[][Access_Code]):m_revenue(0)
{
    for(unsigned short titles = 0; titles < Max_Titles; titles++)
        for(unsigned short copies = 0; copies < Max_Copies; copies++)
            m_inventory[titles][copies] = inventory[titles][copies];

    for(unsigned short user = 0; user < Max_Users; user++)
        for(unsigned short codes = 0; codes < Access_Code; codes++)
            m_users[user][codes] = users[user][codes];
}
void BlueBox::screen()
{
    char answer;

    do
    {
        cout << "BlueBox Video Center\n\nMain Menu: \n" <<
                "1. Rent\n2. Returns\n3. Admin\n4. EXIT\n \nAnswer: ";
        cin >> answer;

        system("CLS");

        switch(answer)
        {
        case '1':
            {
                rent(customer(Users));
                break;
            }
        case '2':
            {
                returns();
                break;
            }
        case '3':
                customer(Admin);
        }
    }while(answer != '4');
}
const unsigned short BlueBox::customer(const unsigned int userType) 
{
    string accessCode;

    if(userType == Users)
        while(true)
        {
            cout << "BlueBox Video Center\n\nCustomer Login:\n Enter Access Code: ";
            cin >> accessCode;

            system("CLS");

            for(unsigned short user = 0; user < Max_Users - 1; user++)
                if(m_users[user][Access_Code - 1] == accessCode)
                    return user;
        }
    else if(userType == Admin)
        while(true)
        {
            cout << "\t\t\tBlueBox Video Center\n\nADMIN Login:\n\nEnter Access Code: ";
            cin >> accessCode;

            system("CLS");

            if(m_users[Max_Users - 1][Access_Code - 1] == accessCode)
            {
                admin();

                break;
            }
        }

    return true;
}
void BlueBox::rent(const unsigned int user)
{
    unsigned short titleCounter = 0;
    char answer;

    while(true)
    {
        cout << "\t\t\tBlueBox Video Center\nWelcome " <<
                m_users[user][0] << "!\n\nWhich title to Rent:\n\n";

        for(unsigned short titles = 0; titles < Max_Titles; titles++)
            if(m_inventory[titles][Max_Copies - 1].at(0) > '0')
                cout << ++titleCounter << ". " << setw(12) << m_inventory[titles][0] << " | " <<
                     m_inventory[titles][Max_Copies - 1] << " copies left\n";

        if(titleCounter == 0)
            error("No DVDS To Rent - Out Of Order! Sorry for the inconvenience\n");

        cout << ++titleCounter << ". Exit\n\nAnswer: ";
        cin >> answer;

        system("CLS");

        if(answer - 48 == titleCounter)
            break;
        else if(answer - 48 > titleCounter || answer - 48 < 1)
        {
            titleCounter = 0;

            continue;
        }
        else
        {
            unsigned short titlePickerCounter = 0;

            for(unsigned short titles = 0; titles < Max_Titles; titles++)
            {
                if(m_inventory[titles][Max_Copies - 1].at(0) > '0')
                    titlePickerCounter++;

                if(answer - 48 == titlePickerCounter)
                {
                    m_inventory[titles][Max_Copies - 1].at(0)--;

                    break;
                }
            }
        }

        titleCounter = 0;
    }
}
void BlueBox::returns()
{
    unsigned short titleCounter = 0;
    char answer;

    while(true)
    {
        cout << "\t\t\tBlueBox Video Center\n\nWhich Title to Return:\n---\n";

        for(unsigned short titles = 0; titles < Max_Titles; titles++)
            if(m_inventory[titles][Max_Copies - 1].at(0) < '2')
                cout << ++titleCounter << ". " << setw(12) << m_inventory[titles][0] << " | " <<
                     2 - atoi(m_inventory[titles][Max_Copies - 1].c_str()) << " copies missing\n";

        if(titleCounter == 0)
        {
            system("CLS");

            return;
        }

        cout << ++titleCounter << ". Exit\n---\nAnswer: ";
        cin >> answer;

        system("CLS");

        if(answer - 48 == titleCounter)
            break;
        else if(answer - 48 > titleCounter || answer - 48 < 1)
        {
            titleCounter = 0;

            continue;
        }
        else
        {
            unsigned short titlePickerCounter = 0;

            for(unsigned short titles = 0; titles < Max_Titles; titles++)
            {
                if(m_inventory[titles][Max_Copies - 1].at(0) < '2')
                    titlePickerCounter++;

                if(answer - 48 == titlePickerCounter)
                {
                    m_inventory[titles][Max_Copies - 1].at(0)++;

                    sales(m_inventory[titles][0]);

                    break;
                }
            }
        }

        titleCounter = 0;
    }
}
void BlueBox::sales(const string& titleName)
{
    cout << "Thank you for returning " << titleName << " within 24 hours!\n---\n";
    cout << "That will cost you $1.00 - Thank you for your business!\n\n";

    system("PAUSE");
    system("CLS");

    m_revenue++;
}
void BlueBox::admin() const
{
    cout << "\t\t\tBlueBox Video Center\n\nAdmin Panel:\n---\n\nCurrent DVDs IN_STOCK:\n-\n";

    for(unsigned short titles = 0; titles < Max_Titles; titles++)
        if(m_inventory[titles][Max_Copies - 1].at(0) > '0')
            cout << setw(12) << m_inventory[titles][0] << " | " <<
                     m_inventory[titles][Max_Copies - 1] << " copies\n";

    cout << "Total Revenue:\n-\n$" << m_revenue << ".00\n\n";

    system("PAUSE");
    system("CLS");
}