Help w/adjustment to program

The following code works well, it takes input from sample.txt which is just a list of five integers. The main, as you can see, just adds, subtracts, etc. Here is code, then I'll tell you what I want to change:

Code:

#include<iostream.h>
#include<fstream.h>

struct Node{
	char digit;
	Node *next;
};

class BigInt{
	int Num;
public:
	friend BigInt operator+(BigInt A, BigInt B);
	friend BigInt operator-(BigInt A, BigInt B);
	friend istream& operator>>(istream& in, BigInt &B);
	friend ostream& operator<<(ostream& o, BigInt &B);
};

BigInt operator+(BigInt A, BigInt B)
{
	A.Num += B.Num;
	return A;
}

BigInt operator-(BigInt A, BigInt B)
{
	A.Num -= B.Num;
	return A;
}

istream& operator>>(istream& in, BigInt &B)
{
	in >> B.Num;
	return in;
}

ostream& operator<<(ostream& o, BigInt &B)
{
	o << B.Num;
	return o;
}


void main()
{
	BigInt v1, v2, v3, v4, v5;

	ifstream in;

	in.open("sample.txt");

	in >> v1 >> v2 >> v3 >> v4 >> v5;

	cout << v1+v2 << endl;
	cout << v3-v4 << endl;
}

Ok, I want to change:

Code:

class BigInt{
	int Num;

to:

Code:

class BigInt{
	Node *Num;

How do I change the overload operator functions to accomodate this??
Thanks!!

PHP Code:

BigInt operator+(BigInt A, BigInt B)
{
    A.Num->digit += B.Num->digit;
    return A;
} 


Thanks disolve.....now my output is letters??? Here is the overload functions I have in place:

Code:

BigInt operator+(BigInt A, BigInt B)
{
    A.Num->digit += B.Num->digit;
    return A;
}

BigInt operator-(BigInt A, BigInt B)
{
    A.Num->digit -= B.Num->digit;
    return A;
}

istream& operator>>(istream& in, BigInt &B)
{
	in >> B.Num->digit;
	return in;
}

ostream& operator<<(ostream& o, BigInt &B)
{
	o << B.Num->digit;
	return o;
}

That's because 'digit' is type char.. I assumed when you said you wanted Node *Num that you wanted to use 'Node.digit' for storage.. change digit to int if so.

hmmm....I want to use Node.digit as storage, but as char...but output as int's...does that make sense??? I can't figure this darn thing out!!

Ok, it's occurred to me I need some sort of insert function. I'm not a good coder, so please bear with me. This is my current code, and my errors follow:

Code:

#include<iostream.h>
#include<fstream.h>

struct Node{
	char digit;
	Node *next;
};

class BigInt{
	Node *Num;
	int cap;
	int top;
public:

	void insert ( int);
	void remove (int);
	int isEmpty () {return !top;};
	int isElement (int);
	int size() {return top;};
	friend BigInt operator+(BigInt A, BigInt B);
	friend BigInt operator-(BigInt A, BigInt B);
	friend istream& operator>>(istream& in, BigInt &B);
	friend ostream& operator<<(ostream& o, BigInt &B);
};

int BigInt::isElement (int target)
{
	for (int i=0; i < top; i++)
		if (Num [i] == target) //<Error 1	

	        return 1;

	return 0;
}

void BigInt::insert (int target)
{
	if (isElement(target))
		return;

	if (top == cap) {
		Node *temp = new Node [cap + 5];
		for (int i=0; i<top; i++) temp [i] = Num->next [i];
		cap =+5;
		delete []Num;
		Num->next = temp;
	}
	Num->next [top++] = Num.target; //<ERROR 2
}

void BigInt::remove (int target)
{
	char i;

	if (! isElement (target))
		return;

	for (i = 0; i < cap; i ++)
		if (Num[i] == target) //<ERROR 3
			break;

		while (i < cap -1){
			Num [i] = Num [i+1];
			i++;
		}
		top --;
}

BigInt operator+(BigInt A, BigInt B)
{
    A.Num->digit += B.Num->digit;
    return A;
}

BigInt operator-(BigInt A, BigInt B)
{
    A.Num->digit -= B.Num->digit;
    return A;
}

istream& operator>>(istream& in, BigInt &B)
{
	in >> B.Num->digit;
	return in;
}

ostream& operator<<(ostream& o, BigInt &B)
{
	o << B.Num->digit;
	return o;
}



void main()
{
	BigInt v1, v2, v3, v4, v5;

	ifstream in;

	in.open("sample.txt");

	in >> v1 >> v2 >> v3 >> v4 >> v5;

	cout << v1+v2 << endl;
	cout << v3-v4 << endl;
}

Errors:

ERROR 1>> error C2676: binary '==' : 'struct Node' does not define this operator or a conversion to a type acceptable to the predefined operator

ERROR 2>> error C2228: left of '.target' must have class/struct/union type

ERROR 3>> error C2676: binary '==' : 'struct Node' does not define this operator or a conversion to a type acceptable to the predefined operator
Error executing cl.exe.