0

The below code, is a source code which i am trying to learn double linked lists from, as for a 2nd year assignment.

For some reason my editor keeps returning the error messages

```
'cout' : undeclared identifier
'cin' : undeclared identifier
```

Can someone please help me??

All help is VERY much appreciated

```
/* Strictly --- Enter Only Integer Data otherwise It'll go in Infinite Loop */
#include <iostream>
#include <process.h>
class doubly
{
doubly * next;
doubly * pre;
int data,ch;
public:
doubly * link(doubly * );
void traverse (doubly * );
};
doubly * doubly::link(doubly * temp)
{
doubly * newlink;
doubly * cur;
newlink = new doubly;
cout<<"\nEnter Element (only possitive number):";
cin>>data;
cur = temp;
if(temp == NULL)
{
newlink->data = data;
newlink->pre = NULL;
newlink->next = NULL;
temp = newlink;
return temp;
}
else
{
while(cur->next != NULL)
{
cur = cur->next ;
}
newlink->data = data;
newlink->pre = cur;
newlink->next = NULL;
cur->next = newlink;
return temp;
}
}
void doubly::traverse(doubly *temp)
{
int ch;
doubly * dummy;
dummy = temp;
cout<<"\n[1] Start From Begainning\n[2] Start From End\n";
cout<<"\nEnter Your Choice :";
cin>>ch;
switch(ch)
{
case 1:
if(dummy != NULL)
{
while(temp->next !=NULL)
{
cout<<temp->data<<endl;
temp=temp->next;
}
if (temp->next == NULL)
cout<<temp->data<<endl;
}
break;
case 2:
if(temp != NULL)
{
temp = dummy;
while(dummy->next !=NULL)
{
dummy=dummy->next;
}
while(dummy->pre !=NULL)
{
cout<<dummy->data<<endl;
dummy=dummy->pre;
}
if (dummy->pre == NULL)
cout<<dummy->data<<endl;
}
break;
}
}
void main()
{
doubly *first=NULL,d1;
int choice;
while(1)
{
cout<<"\n************** DOUBLY LINK LIST **************\n\n";
cout<<"Choices Are :-\n=>[1] For Insert \n=>[2] For Traverse \n=>[3] For Exit";
cout<<"\n\nEnter Your choice : ";
cin>>choice;
switch (choice)
{
case 1:
first=d1.link(first);
break;
case 2:
d1.traverse(first);
break;
case 3:
exit(0);
}
}
}
```