what is wrong is this link list?

/*
can yoou please tell me what is wrong with this linklist? i think it is overiding during my read.But how to fix it?

*/

// Created by: Pierre-Michel Jean-Louis
// Date: Febuary 29th 2003
// File name: exercise2.cc
// Purpose: Reads linklist to a file
// input: list.txt
// output: onscreen

# include <iostream.h>
# include <fstream.h>
# include <iomanip.h>
# include <stdlib.h>
# include <string.h>
# include <ctype.h>
# include <stddef.h>
# include <math.h>

struct nodetype;
typedef int itemtype;
typedef nodetype * ptrtype;


struct nodetype
{
itemtype item;
ptrtype link;
};


int main()
{
ptrtype head;
ptrtype newp;
ptrtype currentp;
itemtype temp;
ifstream file;
file.open("list.txt");
head = new nodetype;
file >> head->item;
if (file)
{
currentp = head;
file >> temp;

while (file)
{
newp = new nodetype;
newp->item = temp;
currentp->link = newp;
file >> temp;
}
currentp->link = NULL;
}
else
head = NULL;
currentp = head;
while(currentp != NULL)
{
cout << currentp->item <<endl;
currentp = currentp->item;
}




return 0;
}

Code:

/*
can yoou please tell me what is wrong with this linklist? i think it is overiding during my read.But how to fix it?

*/

// Created by: 	Pierre-Michel Jean-Louis
// Date:	Febuary 29th 2003
// File name: 	exercise2.cc
// Purpose:	Reads linklist to a file 
// input:	list.txt
// output:	onscreen

# include <iostream.h>
# include <fstream.h>

struct nodetype;
typedef int itemtype;
typedef nodetype * ptrtype;


struct nodetype
{
	itemtype item;
	ptrtype link;
};


int main()
{
	ptrtype head, newp, currentp;
	itemtype temp;
	ifstream file;  

	file.open("list.txt");

	head = new nodetype;
	file >> head->item;
	if (file)
	{
		currentp = head;
		file >> temp;
		
		while (file)
		{
			newp = new nodetype;
			newp->item = temp;
			currentp->link = newp;
			file >> temp;
		}
		currentp->link = NULL;
	}
	else 
		head = NULL;
	currentp = head;
	while(currentp != NULL)
	{
		cout << currentp->item <<endl;
		currentp = currentp->item;
	}
		
	

	
	return 0;
}

May I ask why you need all those headers? As far as I can tell, all you need is iostream and fstream... perhaps even just fstream, as it includes iostream.

you never closed the file

Code:

int main()
{
  ptrtype head;
  itemtype temp;
  head = new nodetype;
  file >> head->item;
  if (file)
  {
     currentp = head;
     file >> temp;

In the code snippet above neither temp nor head->item are initialized to a valid value before you try to write them to the file. You are writing junk to the file.