Question

Write a C++ program to allow an user to enter username and password, and then compare the entered values with the values which stored in a file called login.txt. Display an message "Login successful" if the values are matched, otherwise display "Login fail!. This program allow the user to have three times of tries, if exceeded the number of times, display a message "Number of times is exceeded, please contact administrator

(Assume, the stored username is "INTI-IU and password is "1234567)

Answer 1

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

// Function to read user id and password from file
// Returns user id and password by reference
void readFile(string &userId, string &password)
{
// ifstream class object declared to write data from file
ifstream fileRead;

// Opens both the file for reading
fileRead.open("loginData.txt");

// Checks if the file unable to open for reading display's error message and stop
if(!fileRead)
{
cout<<"\n ERROR: Unable to open the file for reading.";
exit(0);
}// End of if condition

// Reads user id and password
fileRead>>userId>>password;
// Close the file
fileRead.close();
}// End of function

// Function to accept user id and password from user
// Returns user id and password by reference
void acceptIdPassword(string &id, string &pass)
{
fflush(stdin);

// Accepts user id and password
cout<<"\n Enter user id: ";
cin>>id;
cout<<"\n Enter password: ";
cin>>pass;
}// End of function

// Function to check user id and password and returns success status
int login(string userId, string password, string id, string pass)
{
// Checks if system userId and user entered id is equal
if(userId.compare(id) == 0)
{
// Checks if system password and user entered password is equals
if(password.compare(pass) == 0)
// Returns 1 for login successful
return 1;
// Otherwise returns 3 for invalid password
else
return 3;
}// End of if condition

// Otherwise returns 2 for invalid user id
else
return 2;
}// End of function

// main function definition
int main()
{
// Counter for 3 attempts
int counter = 0;
// To store system and user entered user id and password
string userId, password, id, pass;

// Calls the function to read user id and password from file
readFile(userId, password);

// Loops 3 attempts
do
{
// Calls the function to accept user id and password from user
acceptIdPassword(id, pass);

// Calls the function to check login status
// and stores return login status
int status = login(userId, password, id, pass);
// Increase the number of attempts counter by one
counter++;

// Checks if status is 1 then login successful come out of the loop
if(status == 1)
{
cout<<"\n Login successful.";
break;
}// End of if condition

// Otherwise checks if status is 2 then display invalid user id
// continue the loop
else if(status == 2)
cout<<"\n Login fail! \t Invalid user id.";

// Otherwise checks if status is 3 then display invalid password
// continue the loop
else if(status == 3)
cout<<"\n Login fail! \t Invalid user password.";

  // Checks if counter value is more than 3 then display error message
if(counter == 3)
cout<<"\n Number of times is exceeded, please contact administrator";
}while(counter < 3); // End of do - while loop

}// End of main function

Sample Output 1:

Enter user id: pyari

Enter password: 1234567

Login fail! Invalid user id.
Enter user id: INTI-IU

Enter password: 123

Login fail! Invalid user password.
Enter user id: INTI-IU

Enter password: 1234567

Login successful.

Sample Output 2:

Enter user id: Pyari

Enter password: 1234567

Login fail! Invalid user id.
Enter user id: INTI-IU

Enter password: 12345

Login fail! Invalid user password.
Enter user id: INTI-IU

Enter password: 123456789

Login fail! Invalid user password.
Number of times is exceeded, please contact administrator