I need help with appending and retrieving information from the un() part of this program. I am trying to think of different ways to get information to and from a text file. If you could help I would be greatly appreciative. Thanks, kiknwing.

Code:
#include "stdafx.h"

class Index
{
	ofstream myFile;
	HANDLE np;
	unsigned threadID;


	char selection;
	string user;


public : 
	
	Index(void);
	~Index(void);
	int m(void);		//menu
	void r(void);		//register
	void l(void);		//login			
	void un (void);		//username
	void pw (void);		//password
	void notepad(void);
	
	static unsigned int __stdcall notepadThread(void* arg);
	void AI (void);


	void c(void);	//clearscreen
	void p(void);	//pause


} index;




int Index::m(void)
{
	c();
	
	cout<<"Register = 1\nLogin = 2"<<endl;
	cin>>selection;
	
	switch (selection)
	
	{
	
	case '1' : {	AI();
	break;
			   }
	
	case '2' : {	AI();
	break;
			   }


	default : { cout<<"nope";
	break;
			  }
	}
	 
	return 1;
}


void Index::AI(void)
{
	if (selection == 1 || 2)
	{ 
		c();
		cout<<"Please Enter Your Username."<<endl<<"Username: ";
		cin>>user;
		un();
	}
}


Index::~Index (void)
{


}


void Index::un(void)
{
	
}


void Index::pw(void)
{


}


Index::Index (void) {
np = 0;
}


unsigned int __stdcall Index::notepadThread(void* arg) {
system("notepad.exe record.txt");
_endthreadex(0);
arg = 0;
return 0;
}


void Index::notepad(void) {
np = (HANDLE)_beginthreadex( NULL, 0, &Index::notepadThread, np, 0, &threadID );
}


void Index::c(void)
{
	system("CLS");
}


void Index::p(void)
{
	system("pause");
}


int _tmain(int argc, _TCHAR* argv[])
{
Index index;
while(index.m());
return 0;
}