i get an error that "unhandled exception at (msvcr100d.dll) in .exe access violation reading location" in following programme

#include<iostream>
#include<conio.h>
#include<fstream>
#include<process.h>
#include<string>

using namespace std;

class bus
{
private:
	int busno,seat_no;
	string driver_name,destination,start_station,arrival_time,departure_time;
public:
	bus()
	{
	busno=0;
	seat_no=0;
	driver_name="";
	destination="";
	start_station="";
	arrival_time="";
	departure_time="";
	}
	void get_bus_info()
	{
	cout<<"Enter busno : ";
	cin >> busno;
	cout<<"Enter Driver name : ";
	cin>>driver_name;
	cout<<"From : ";
	cin>>start_station;
	cout<<"To : ";
	cin>>destination;
	cout<<"Enter arrival time : ";
	cin>>arrival_time;
	cout<<"Enter departure time : ";
	cin>>departure_time;
	cout<<"Enter Total no of seats : ";
	cin>>seat_no;
	}

	int getbusno()
	{
	return busno;
	}

	void display()
	{
	cout<<busno<<"\t"<<driver_name<<"\t"<<start_station<<"\t"<<destination<<"\t"<<arrival_time<<"\t"<<departure_time<<"\t"<<seat_no<<"\t"<<endl;
	}
};

class bus_reservation_user
{
public:
	void do_reservation()
	{
	cout<<"do bus info ";
	}
	void check_bus_availability()
	{
	cout<<"check bus info ";
	}
	void cancel_reservation()
	{
	cout<<"cancel bus info ";
	}
};

class bus_reservation_admin:public bus_reservation_user
{
private:
	char username[25];
	char password[5];
public:
	void add_bus_info(int i)
	{
	bus b;
	if(i==1)
	{
	ofstream ofile;
	ofile.open("bus_reservation.dat",ios::binary|ios::app);
	b.get_bus_info();
	ofile.write(reinterpret_cast<char*>(&b), sizeof(b));
	ofile.close();
	cout<<"Bus information added sucessfully!!!!"<<endl;
	}

	else if(i==3)
	{
	cout<<"Bus no\tDriver name\tFrom\tTo\tarrival time\tdeparture time\tTotal no of seats"<<endl;
	
	ifstream ifile;
	ifile.seekg(1,ios::beg);
	ifile.open("bus_reservation.dat",ios::binary|ios::in);

	while(ifile.read(reinterpret_cast<char*>(&b), sizeof(b)))
	{
	//ifile.read(reinterpret_cast<char*>(&b), sizeof(b));
	b.display();
	}
	ifile.close();
	}
	}

	void delete_bus_info()
	{
	cout<<"delete bus info ";
	}

	void check_username_password();

	void display_all_bus_info()
	{
	
	cout<<"Bus no\tDriver name\tFrom\tTo\tarrival time\tdeparture time\tTotal no of seats"<<endl;
	bus b1;
	ifstream ifile;
	ifile.seekg(1,ios::beg);
	ifile.open("bus_reservation.dat",ios::binary|ios::in);

	while(ifile.read(reinterpret_cast<char*>(&b1), sizeof(b1)))
	{
	//ifile.read(reinterpret_cast<char*>(&b), sizeof(b));
	b1.display();
	}
	ifile.close();
	}
	
	
};


void bus_reservation_admin::check_username_password()
{
char c[]="admin";
cout<<"Enter username ";
cin>>username;
cout<<"Enter Password ";
for(int i=0;i<5;i++)
    {
       password[i]=getch();
       cout<<"*";
    }
int a=0;
for(int j=0;j<5;j++)
    {
        if(password[j]==c[j])
		{
		a+=1;
		}
    }

int opt;
cout<<endl;
if(strcmp(username,"admin")==0 && a==5)
	{
		cout<<"1.Add new bus information"<<endl;
		cout<<"2.Delete Bus information"<<endl;
		cout<<"3.Display all bus information"<<endl;
		cout<<"4.Exit"<<endl;
		cout<<"Enter option ";
		cin>>opt;
		switch(opt)
			{
			case 1:
			add_bus_info(1);
			break;

			case 2:
			delete_bus_info();
			break;

			case 3:
			add_bus_info(3);
			//display_all_bus_info();
			break;

			case 4:
			exit(1);
			break;

			default:
			cout<<"Sorry wrong option!!!!!!!!!!!!!!!!";
			break;
			}
	}
else
	{
	cout<<"Wrong password or username;";
	}
};

void main()
{
	cout<<"-------------------BUS RESERVATION SYSTEM--------------"<<endl;
	cout<<"Name : LIKHITA ASHOK KADAM (A-12)"<<endl;
	cout<<"       SHRUTIKA SANJIVAN DESHMUKH (A-07)"<<endl;
	cout<<"Project Guide : "<<endl;
	int option;
	cout<<"1.Admin"<<endl;
	cout<<"2.Bus reservation"<<endl;
	cout<<"3.Exit"<<endl;
	cout<<"Enter option ";
	cin>>option;

	bus_reservation_admin bsr;
	switch(option)
	{
	case 1:
	bsr.check_username_password();
	break;

	case 2:
	bsr.do_reservation();
	break;

	case 3:
	exit(1);
	break;

	default:
	cout<<"Sorry Wrong input";
	break;
	}
getch();
}