How can i incorporate polymorphism into this program without changing it too much?

[yin]

Does my program employ any operator or function overloading? If not, is there any way i can incorporate it without changing it too much?

#include <iostream>
using namespace std;
#include <fstream>
#include <string>

class user {
	public:
		char choice1;		
		string newpass;
		fstream usernames;
		fstream pswd;
		fstream npswd;
		fstream rnusernames;
		fstream rnpass;
		fstream rmaide;
};

class login : public user {
	private:
	string temp;
	string temp1;
	string temp2;
	string username;
	string userpass;
	string newuserpass;
	string loginyn;
	string mynewpass;

	public:
		int checkusername(){
		usernames.open("names.txt");
		cout << "\nplease enter your username   ";
		cin >> username; 
		while ((usernames >> temp)) { 
			if (temp.compare(username) == 0) {
				//cout << "found";
				usernames.close();
				return 1;
			}
		}
		usernames.close();
		return 0;
		}
		int checkpassword(){
		cout<<"please enter your password   ";
		cin>>userpass;
		pswd.open("pass.txt");
			while (pswd >> temp1) { 
				if (temp1.compare(userpass) == 0){
					cout<<"\n[ "<<username<<" ] having password [ "<<userpass<<" ] has been found in the database.\n\n";
					pswd.close();
					return 1;
				}
			}
		pswd.close();
		return 0;
		}
		int checknewpassword(){
		cout<<"please enter your password   ";
		cin>>newuserpass;
		npswd.open("newpass.txt");
			while (npswd >> temp2) { 
				if (temp2.compare(newuserpass) == 0){
					cout<<"Congratulations!!! You have successfully logged in with your new password.";
					npswd.close();
					return 1;
				}
				else{
					cout<<"ACCESS DENIED";
				}
			}
		npswd.close();
		return 0;
		}
		int creatnewpass(){
		cout<<"Password: ";
		cin>>mynewpass;
		npswd.open("newpass.txt");
		npswd<<mynewpass;
		npswd.close();
			cout<<"\nLogin now? (y/n) ";
		cin>>loginyn;
			if(loginyn=="y"){
				cout<<"\n        [LOGIN PROCESS STARTING...]\n";
				checkusername();
				checknewpassword();
			}
		return 0;
		}
		private:
};

class registration :  public user {
	private:
	string nusername;
	string rpass;
	string maiden;

	public:
		void askusername(){
			cout<<"\nUsername: ";
			cin>>nusername;
			rnusernames.open("newnames.txt");
			rnusernames<<nusername;
			rnusernames.close();
		}

		void askuserpass(){
			cout<<"Password: ";
			cin>>rpass;
			rnpass.open("newpass.txt");
			rnpass<<rpass;
			rnpass.close();
		}

		void askMMN(){
			cout<<"Mother's maiden name: ";
			cin>>maiden;
			rmaide.open("maidennames.txt");
			rmaide<<maiden;
			rmaide.close();
		}
};

int main() {
registration r;
user u;   
login verify; 
int attempts, success;
cout<<"\nAre you a new user? (y/n) ";
cin>>u.choice1;
	if (u.choice1 == 'n'){
		for (attempts = 1; attempts < 4; attempts++){
			success = verify.checkusername();
				if (success == 1) { 
					break; 
				}
			}
		if (success == 0){
			cout<<"\nACCESS DENIED\n";
			cin.ignore();
			abort();
		}
		verify.checkpassword();
		cout<<"would you like to create a new password? (y/n) ";
		cin>>u.newpass;
			if (u.newpass=="y"){
				verify.creatnewpass();
			}
			else if (u.newpass=="n"){
				cin.ignore();
				abort();
			}
	}
	else if (u.choice1 == 'y'){
		r.askusername();
		r.askuserpass();
		r.askMMN();
		cin.ignore();
		abort();
	}
	else {
		cout<<"Error";
	}
return 0;
}

[TheToaster]

The first thing I notice is your concept of inheritance itself is wrong.

The way you have it set up is that login is-a user, and registration is-a login, and thus registration is a user (?) That doesn't make any sense. There is no real need for inheritance or polymorphism in this hierarchy at all, and most of the class methods are extremely repetitive. You could have just made a single user class with the methods register() and login(). Everything else could be abstracted.

There is no need to make things complicated.

[yin]

i know but that's how the assignment is laid out. I do see your point and will change them to old user and new user. i know doing all this stuff isn't necessary but it's the objective of the assignment.

[TheToaster]

Did the assignment tell you to make a class called "user" that is the base class of "registration" and 'login"?