Calculator

#include <iostream>
#include <iomanip>
#include <cstdlib>
#include <sstream>
#include <string>
#include <cmath>
#include <vector>
#include <exception>
#include <ctime>
#include <ctype.h>

using std::cout;
using std::cin;
using std::endl;
using std::string;
using std::vector;
using std::stringstream;

void DrawLine (string Str, int Len = 80)
{
    int x = 0;
    cout << endl;
    for (int i = 0; i < Len;i++)
    {
        cout << Str[x];
        if (x == Str.size())
            x = 0;
    }
    if (Len != 80)
        cout << endl;
}

class Calculator
{
private:
    long double Num1;
    long double Num2;
public:
    void SetVal(int, int);

    long double Add ();
    long double Subtract();
    long double Multiply();
    long double Divide();
    int Mod();
    long double Expon();
}
calculator,
*Calc;

void Calculator::SetVal(int a, int b)
{
    Num1 = a;
    Num2 = b;
}

long double Calculator::Add()
{
    return Num1 + Num2;
}

long double Calculator::Subtract()
{
    return Num1-Num2;
}

long double Calculator::Multiply()
{
    return Num1*Num2;
}

long double Calculator::Divide ()
{
    return Num1/Num2;
}

int Calculator::Mod()
{
    return ((int(Num1))% (int(Num2)));
}

long double Calculator::Expon()
{
    int X = 1;
    if (Num2 < 0)
    {
        for (int i = 0; i < int(Num2); i++)
        {
            X *= Num1;
        }
    return X;
    }

    else if (Num2 == 0)
        return 1;
    else if (Num2 < 0)
    {
        Num2 *= (-1);
        for (int i = 0; i < int(Num2); i++)
        {
            X *= Num1;
        }
        X /= X*X;
    return X;
    }
}

int main ()
{
    stringstream Ent1, Ent2, Oper;
    bool Check1 = true;
    bool Check2 = false;
    string Action;
    int x, y;
    string a , b;

    Calc =  &calculator;
    cout << "This calculator can calclulate a couple of thing that listed are in the Table shown below.";
    cout << "To tell the computer wha to calculate simply write the Expression.\n";
    cout << "NOTE: 1. Only one operator & two Numbers are allowed in the expression.\n";
    cout << "2. No variables are allowed";

    cout << "What do you want to calculate:  ";
    getline (cin, Action);


    for (int i = 0; i < Action.size(); i++)
    {
        if (isdigit(Action[i]) && Check1)
        {
            Ent1 << Action[i];
        }

        else if (!isalnum(Action[i]))
        {
            Oper << Action[i];
            Check1 = false;
            Check2 = true;
        }

        else if (isdigit(Action[i]) && Check2)
        {
            Ent2 << Action[i];
        }
    }

    a = Ent1.str();
    b = Ent2.str();

    x = atoi(a.c_str());
    y = atoi(b.c_str());

    Calc -> SetVal(x,y);



    ;cout << "\n\nPress Enter to exit . . .";
    cin.sync();
    cin.get();
    return 0;
}