Is my class bypassing my do/while loop?

[andyman105070]

My program for homework is nearly completed. However, my input validation which is inside the class member getData (rational.getData) is not breaking when its supposed too. For example if user inputs 2/0, it should read "DIVISION BY ZERO ERRROR! " and then break, starting the do while loop over for another input. In previous programs (this is my first one utilizing class/struct) this format has worked fine, but i wonder if the way the class is set up, that the compiler will accept any data, despite the boolean foundFlag signaling true. Also, if you look at my "Check" function which puts out the "reduced form", if Standard Input goes (0/2) it should just print out "0", but its output will do the "O" and also "0/2".
I hope this information can be addressed. I personally just started programming at the end of August, with no prior experience, and I was just looking at my previous posts, and I am dumbfounded at the progression I have made. To all people on here who help noobs like myself. It is greatly appreciated. Thank You.

  #include<iostream>
#include<iomanip>

using namespace std;

class rational
{
private:
	int numerator, denominator;
public:

	void reduce2();
	rational(); //constructor
	void getData();
	void printToConsole();
	rational operator * (const rational &c2);
	rational operator / (const rational &c2);
	rational operator + (const rational &c2);
	rational operator - (const rational &c2);
	bool foundFlag;
	void Check();
	double Evaluate();


};
rational::rational() // rational a
{ 

}
void rational:: Check()
{
	cout << "\nJust Checking...Reduced Form Is:";
	reduce2();
	if(numerator==0&&denominator!=0)
	{	
		cout<< " == 0"<<endl;
	}
	if((numerator==denominator)&&numerator!=0)
	{
		cout << "  == 1"<<endl;
	}
	if ((denominator == 1)&& numerator!=0)
	{
		cout<< " == "<< numerator<<endl;
	}
	else 
		cout<< " == " << numerator<<"/"<<denominator<<endl;
}

rational rational::operator +(const rational &c2)
{
	rational temp;
	fflush(stdin);
	temp.denominator=rational::denominator*c2.denominator;
	temp.numerator= (rational::numerator*c2.denominator)+(c2.numerator*rational::denominator);
	cout<< numerator<<"/"<<denominator<< " + "<< c2.numerator<<"/"<<c2.denominator<<" == ";
	cout<< temp.numerator<< "/"<< temp.denominator;


	return temp;
}


rational rational:: operator -(const rational &c2)
{
	fflush(stdin);
	rational temp;
	temp.denominator=rational::denominator*c2.denominator;
	temp.numerator= (rational::numerator*c2.denominator)-(c2.numerator*rational::denominator);
	cout<< numerator<<"/"<<denominator<< " - "<< c2.numerator<<"/"<<c2.denominator<<" == ";
	cout<< temp.numerator<< "/"<< temp.denominator;
	return temp;
}

double rational::Evaluate()
{ 
	fflush(stdin);
	double n = numerator;
	double d = denominator;
	cout<<" == : "<<fixed<<setprecision(2)<< n/d<<endl;
	return (n/d);
}
rational rational :: operator *(const rational &c2)
{ 
	fflush(stdin);
	rational temp;
	temp.numerator=numerator*c2.numerator;
	temp.denominator=denominator*c2.denominator;

	cout<< numerator<<"/"<<denominator<< " * "<< c2.numerator<<"/"<<c2.denominator<<" == ";
	cout<< temp.numerator<< "/"<< temp.denominator;
	return temp;
}
rational rational :: operator /(const rational &c2)
{
	fflush(stdin);
	rational temp;
	temp.numerator= numerator*c2.denominator;
	temp.denominator=denominator*c2.numerator;
	cout<< numerator<<"/"<<denominator<< " / "<< c2.numerator<<"/"<<c2.denominator<<" == ";
	cout<< temp.numerator<< "/"<< temp.denominator;

	return temp;
}

void rational:: reduce2()
{
	int tmpNum, tmpDen, n;

	if (denominator < 1)
	{
		numerator = numerator * -1;
		denominator = denominator * -1;
	}//end if
	//reduce to lowest terms

	//need abs to find gcd
	tmpNum = abs(numerator); //temporary numerator becomes absoluted.
	tmpDen = abs(denominator);


	if (tmpDen > tmpNum){
		n = tmpDen;
		tmpDen = tmpNum;
		tmpNum = n;
	}//endif


	for(int i = tmpDen; i > 0;i--)
	{
		if((tmpDen % i == 0) && (tmpNum % i == 0))
		{
			numerator = numerator/i;
			denominator = denominator/i;
			break;
		}//endif
	}//endfor
	fflush(stdin);
}


void rational::getData()
{
	do
	{
	char n[20], num[20], den[20];
	bool foundFlag;  // signal invalid entry
	int countDot=0;	 // count how many colon entered so far	
	unsigned len;    // length of input value
	int x = 0;
	
		fflush(stdin);
		cout<<"\n Please enter a fraction in (a/b) format: ";
		countDot = 0; // there was no dot found at first
		foundFlag = false; // there was nothing wrong at first
		fflush(stdin);

		cin.getline(n, 20); // read in a value entered from keyboard
		len = strlen(n);

		if (len == 0)
		{
			cout << "Oops! No value was entered!\n";
			foundFlag = true; // cannot have empty input
			break;
		}
		else 
		{
			int x = 0;
		for (unsigned i = 0;  i<len; i++)  //unsigned is positive integer
		{	
			if ( n[i] == ' ' ) // space was not allowed - like 1 :56
			{	
				cout << "\nspace was not allowed.\n";
				foundFlag = true;
				fflush(stdin);
				break;
			}	
			if(n[i]=='/')
			{
				x=i;
			}
		}
		for (int i=0; i<x; i++)
		{
			if((n[i]<'0' || n[i]>'9') && (n[0]!='-'))
			{
				cout<< "Invalid:\n ";
				foundFlag=true;
				fflush(stdin);
				break;
			}				
			int j=0;
			for (int i=0; i<x; i++)
			{
				num[j]=n[i];
				j++;						
			}
			numerator=atoi(num);
		}
		fflush(stdin);
		int j=0;

		for(int i=x+1; i<len; i++)
		{
			if((n[i]<48||n[i]>57)&& n[x+1]!='-')
			{
				cout<< "Invalid: Not numbers.\n";
				foundFlag=true;
				fflush(stdin);
				break;
			}
			else
			{				
				den[j]=n[i];
				j++;
			}		
			denominator=atoi(den);
		}
		if(denominator == 0)
		{
			cout<< "\nERROR DIVISION BY ZERO! TRY AGAIN!";
			foundFlag=true;
			break;
			fflush(stdin);
		}
		}
	}while(foundFlag==true);
	
}



int main()
{
	char again;
	do
	{
		rational c1, c2;
		c1.getData();
		c1.reduce2();
		c1.Check();

		fflush(stdin);
		c2.getData();
		c2.reduce2();
		c2.Check();
		fflush(stdin);
		(c1 + c2).Evaluate();
		(c1 - c2).Evaluate();
		(c1 * c2).Evaluate();
		(c1 / c2).Evaluate();

		cout << "\n\nRun again (y/n)? ";
		fflush(stdin);
		cin >> again;
		while (toupper(again) != 'Y' && toupper(again) != 'N')
		{
			fflush(stdin);
			cout << "Please enter \'y\' for Yes, or \'n\' for No: ";
			cin >> again;			
		}

		fflush(stdin);

		if(again=='y'||again=='Y')
		{
			system("cls");
		}
	}while(again=='y'||again=='Y');
	cout << "\nProgrammer:Andrew HOlder I FREAKING HATE PROGRAMMING!";	
	cout << "Good bye! Press <Enter> key to end the program... ";
	fflush(stdin);
	cin.get();

	return 0;

}