Program in C++ to demonstrate Circular SinglyLinked List.

#include<iostream.h>
#include<stdio.h>
#include<conio.h>
struct node
    {
    int data;
    node *next;
    node *prev;
    };
node * addnode(node*);
void shownodes(node*);
node *delete_node(node*);
node *head;
void main()
{
    clrscr();
    int ch;
    ch=1;
    head=NULL;
    while( ch != 0)
    {
    cout<<"\nMENU\n";
    cout<<"\t1.ADD A NODE\n";
    cout<<"\t2.DISPLAY THE NODES\n";
    cout<<"\t3.DELETION\n";
    cout<<"\t0.QUIT\n";
    cin>>ch;switch(ch)
        {
        case 1:
            head=addnode(head);break;
        case 2:
            shownodes(head);break;
        case 3:
            head=delete_node(head);break;
        case 0:
            ch=0;break;
        default:
            cout<<"INVALID CHOICE  ?? \n";break;
        }
    }
}
node * addnode(node *f)
{
    node *n;
    int ch;
    n=new node;
    cout<<"ENTER A ELEMENT TO BE INSERTED :";
    cin>>n->data;
    n->next=n->prev=NULL;
    if(f==NULL)
    {f=n;cout<<"\nLIST IS EMPTY.. NODE IS INSERTED AT THE BEGINING..\n";}
    else{
    cout<<"WHERE YOU WANT TO INSERT :\n";
    cout<<"From\n\t1.BEG\n\t2.END\n";
    cin>>ch;
    switch(ch)
    {
    case 1:n->next=f;f->prev=n;f=n;cout<<"SUCCESS\n";break;
    case 2:    node *temp=f;
        while(temp->next != NULL)
        {temp=temp->next;}
        temp->next=n;n->prev=temp;cout<<"SUCCESS \n";break;
    default:cout<<"INVALID ??\n";break;}}
    return f;
}
void shownodes(node *f)
{
    node *temp=f;
    if ( temp == NULL ){
    cout<<endl<<"EMPTY LIST ..\n";
    return;}
    else{
    cout<<"HEAD";
    while(temp!=NULL)
    {cout<<" <=> ";
    cout<<temp->data;temp=temp->next;}
    cout<<" -> NULL "<<endl;}
}
node * delete_node(node *f)
{
    node *temp1,*temp2;int ch;
    temp1=temp2=f;
    if( temp1 == NULL ){
    cout<<"\nEMPTY LIST ... CANNOT BE DELETED \n";}
    else{
    cout<<"From\n\t1.BEG\n\t2.END\n";
    cin>>ch;
    switch(ch){
    case 1:f=f->next;cout<<"SUCCESS\n";break;
    case 2: while(temp1->next!=NULL){
        temp2=temp1;temp1=temp1->next;}
        temp2->next=NULL;
        cout<<"SUCCESS \n";break;
    default:cout<<"INVALID ??\n";break;}}
    return f;
}