ADSL Binary Search Tree (BST)

#include <iostream>
using namespace std;

class node
{
public:
int data;
node *left, *right;

};

class BT
{
public:
node *root, *temp;
void create();
void traverse();
void display();
void insert(node *,node *);
void preorder(node *);
void postorder(node *);
void inorder(node *);
BT()
{
root=temp=NULL;
}
};

int main()
{
int ch;
BT obj;
do
{
cout<<"\n1. Create Binary Tree\n2. Traverse Binary Tree\n3. Exit\nSelect your option:";
cin>>ch;
switch(ch)
{
case 1:
cout<<endl<<"\t\t****Create Binary Tree****";
obj.create();
break;
case 2:
obj.display();
break;
default:
    cout<<endl<<"Invalid choice!!!";
    break;
}
}while(ch!=3);
return 0;
}

void BT::display()
{
int ch1;
do
{
cout<<endl<<"\t\t****Traversing a Binary Tree****";
cout<<endl<<"How to Traverse?\n1.Preorder\n2.Postorder\n3.Inorder\n4.Back";
cin>>ch1;
switch(ch1)
{
case 1:
preorder(temp);
break;
case 2:
postorder(temp);
break;
case 3:
inorder(temp);
break;
default:
cout<<endl<<"Invalid option!!!";
break;
}
  }while(ch1!=4);
}

void BT::create()
{
char op;
int val;
node *temp;
do
{
cout<<endl<<"Enter element: ";
cin>>val;
temp=new node;
temp->data=val;
temp->left=NULL;
temp->right=NULL;
if(root==NULL)
{
root=temp;
}
else
{
insert(root,temp);

}
cout<<endl<<"Add more elements?(Y/N)";
cin>>op;
}while(op=='y'||op=='Y');
}

void BT::insert(node *root,node *temp)
{
char op;
cout<<endl<<"Current root: "<<root->data;
cout<<endl<<"Where to insert element?(L/R)";
cin>>op;
if(op=='L'||op=='l')
{
if(root->left==NULL)
root->left=temp;
else
insert(root->left,temp);
}
else
{
if(root->right==NULL)
root->right=temp;
else
insert(root->right,temp);
}
}

void BT::preorder(node *temp)
{
if(temp!=NULL)
{
cout<<endl<<"Preorder: "<<temp->data;
preorder(temp->left);
preorder(temp->right);
}

}

void BT::postorder(node *temp)
{
if(temp!=NULL)
{
postorder(temp->left);
postorder(temp->right);
cout<<endl<<"Postorder: "<<temp->data;
}

}

void BT::inorder(node *temp)
{
if(temp!=NULL)
{
inorder(temp->left);
cout<<endl<<"Inorder: "<<temp->data;
inorder(temp->right);
}

}