Writing Tree data structure in C++

I was browsing through the Facebook and encountered ProudEngineers page. The implementation provided there is awesome.
After going through it, I couldn't resist to mention on this blog so that our readers like you could also benefit from it.
Here is the code:
#include <iostream.h>

#define TRUE 1
#define FALSE 0

class tree
{

	private:

		struct node
		{
			node *l;
			int data;
			node *r;
		}*p;

	public:

		tree();
		void search(int n, int &found, node * &parent);
		void insert(int n);
		void traverse();
		void in(node *q);
		void pre(node *q);
		void post(node *q);
		int operator == (tree t);
		int compare(node *pp, node *qq);
		void operator = (tree t);
		node * copy (node * q);
};

tree::tree()
{
	p = NULL;
}

void tree::search(int n, int &found, node * &parent)
{
	node *q;
	found = FALSE;
	parent = NULL;

	if(p == NULL)
		return;

	q = p;
	while(q != NULL)
	{
		if(q->data == n)
		{
			found = TRUE;
			return;
		}

		if(q->data > n)
		{
			parent = q;
			q = q->l;
		}
		else
		{
			parent = q;
			q = q->r;
		}

	}
}

void tree::insert(int n)
{
	int found;
	node *t,*parent;

	search(n, found, parent);

	if(found == TRUE)
		cout << endl << "such a node already exists";
	else
	{
		t = new node;
		t->data = n;
		t->l = NULL;
		t->r = NULL;

		if(parent == NULL)
			p = t;
		else
			parent->data > n?parent->l = t:parent->r = t;
	}
}

void tree::traverse()
{
	int choice;

	cout << endl << "1. Inorder"
		<< endl << "2. Preorder"
		<< endl << "3. Postorder"
		<< endl << "Your choice ";
	cin >> choice;

	switch(choice)
	{
		case 1:
			in(p);
			break;

		case 2:
			pre(p);
			break;

		case 3:
			post(p);
			break;
	}

}

void tree::in(node *q)
{
	if(q != NULL)
	{
		in(q->l);
		cout << "\t" << q->data;
		in(q->r);
	}
}

void tree::pre(node *q)
{
	if(q != NULL)
	{
		cout << "\t" << q->data;
		pre(q->l);
		pre(q->r);
	}
}

void tree::post(node *q)
{
	if(q != NULL)
	{
		post(q->l);
		post(q->r);
		cout << "\t" << q->data;
	}
}

int tree::operator == (tree t)
{
	int flag;

	flag = compare(p, t.p);
	return flag;
}

int tree::compare(node *pp, node *qq)
{
	static int flag;

	if((pp == NULL) && (qq == NULL))
		flag = TRUE;
	else
	{
		if((pp != NULL) && (qq != NULL))
		{
			if(pp->data != qq->data)
				flag = FALSE;
			else
			{
				compare(pp->l,qq->l);
				compare(pp->r,qq->r);
			}
		}
	}

	return (flag);
}

void tree::operator = (tree t)
{
	p = copy(t.p);
}

tree::node * tree:: copy(node *q)
{
	node *t;

	if(q != NULL)
	{
		t = new node;
		t->data = q->data;
		t->l = copy(q->l);
		t->r = copy(q->r);
		return (t);
	}
	else
		return (NULL);
}

void main()
{
	tree tt, ss;
	int i, num;

	for(i=0; i <= 6; i++)
	{
		cout << endl << "Enter data for the node to be inserted : ";
		cin >> num;
		tt.insert(num);
	}

	tt.traverse();
	ss = tt;
	ss.traverse();

	if(ss == tt)
		cout << endl << "Trees are equal";
	else
		cout << endl << "Trees are unequal";
}