Inserting a node.cpp

#include<iostream>
using namespace std;
class Node
{
	public:
	int data;
	Node* next;
};

void first(Node** head_ref,int new_data)
{
	Node* new_node=new Node();
	
	new_node->data=new_data;
	
	new_node->next=(*head_ref);
	
	(*head_ref) = new_node;
}

void insertAfter(Node* prev_node,int new_data)
{
	if(prev_node==NULL)
	{
		cout<<"the given previous node cannot be NULL"; 
      return; 
    }  
    Node* new_node= new Node();
    
    new_node->data  = new_data; 
    
    new_node->next=prev_node->next;
    
    prev_node->next = new_node; 
}

void append(Node** head_ref, int new_data) 
{
	Node* new_node= new Node();
    Node *last = *head_ref;	
	
	new_node->data  = new_data;
	
	new_node->next = NULL;
	
	if (*head_ref == NULL) 
    { 
       *head_ref = new_node; 
       return; 
    } 
    
    while (last->next != NULL) 
        last = last->next; 
        
    last->next = new_node; 
    return; 	
}
void printList(Node *node) 
{ 
  while (node != NULL) 
  { 
     cout<<node->data; 
     node = node->next; 
  } 
} 

int main() 
{ 
	Node* head = NULL; 
	append(&head, 6);
	first(&head, 7);
	first(&head, 1);
	append(&head, 4); 
	insertAfter(head->next, 8); 
	
	printList(head); 
}