C++ Mini Projects: ATM Simulator

This is an ATM simulator that requires users to log in with a PIN, perform transactions, and log out—just like a real ATM machine. Let's build the software inside the ATM!

Skills Used

• Handling files: Logging all transactions to a file
• Conditional statements: Managing invalid inputs and account rules
• Functions: Breaking down the program into smaller, manageable parts
• Loops: Navigating the menu and handling repeated PIN attempts
• Input and output management: Managing user inputs and displaying outputs

The Code to Build the Project

#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>

using namespace std;

// Function prototypes
bool login(int correctPIN);
void displayMenu();
void checkBalance(double balance);
void deposit(double &balance, ofstream &logfile);
void withdraw(double &balance, ofstream &logfile);
void logTransaction(ofstream &logfile, const string &type, double amount);

int main() {
    const int correctPIN = 1234; // Default PIN
    double balance = 1000.0; // Default balance
    ofstream logfile("transactions.txt", ios::app); // Logfile for transactions

    // Welcome message
    cout << "----- ATM Simulator -----\n";

    // Login process
    if (!login(correctPIN)) {
        cout << "Too many failed attempts. Exiting...\n";
        return 1;
    }

    // Main menu loop
    int choice;
    do {
        displayMenu();
        cout << "Enter your choice: ";
        cin >> choice;

        switch (choice) {
            case 1:
                checkBalance(balance);
                break;
            case 2:
                deposit(balance, logfile);
                break;
            case 3:
                withdraw(balance, logfile);
                break;
            case 4:
                cout << "Thank you for using the ATM!\n";
                break;
            default:
                cout << "Invalid choice. Please try again.\n";
        }
    } while (choice != 4);

    logfile.close(); // Close the log file
    return 0;
}

// Function to handle login
bool login(int correctPIN) {
    int attempts = 0, enteredPIN;
    while (attempts < 3) {
        cout << "Enter your PIN: ";
        cin >> enteredPIN;
        if (enteredPIN == correctPIN) {
            cout << "Login successful!\n";
            return true;
        } else {
            cout << "Incorrect PIN. Try again.\n";
            attempts++;
        }
    }
    return false;
}

// Function to display the menu
void displayMenu() {
    cout << "----- Main Menu -----\n";
    cout << "1. Check balance\n";
    cout << "2. Deposit money\n";
    cout << "3. Withdraw money\n";
    cout << "4. Exit\n";
}

// Function to check the balance
void checkBalance(double balance) {
    cout << "Your current balance: $" << fixed << setprecision(2) << balance << "\n";
}

// Function to deposit money
void deposit(double &balance, ofstream &logfile) {
    double amount;
    cout << "Enter the amount to deposit: $";
    cin >> amount;
    if (amount > 0) {
        balance += amount;
        cout << "Deposit successful. New balance: $" << balance << "\n";
        logTransaction(logfile, "Deposit", amount);
    } else {
        cout << "Invalid amount. Deposit failed.\n";
    }
}

// Function to withdraw money
void withdraw(double &balance, ofstream &logfile) {
    double amount;
    cout << "Enter the amount to withdraw: $";
    cin >> amount;
    if (amount > 0 && amount <= balance) {
        balance -= amount;
        cout << "Withdrawal successful. New balance: $" << balance << "\n";
        logTransaction(logfile, "Withdrawal", amount);
    } else if (amount > balance) {
        cout << "Insufficient balance. Withdrawal failed.\n";
    } else {
        cout << "Invalid amount. Withdrawal failed.\n";
    }
}

// Function to log transactions
void logTransaction(ofstream &logfile, const string &type, double amount) {
    logfile << type << ": $" << fixed << setprecision(2) << amount << "\n";
}

Explanation

Login Process

• The program prompts the user for a PIN.
• The user has three attempts to enter the correct PIN; otherwise, the program exits.

Menu Management

• The displayMenu() function shows the available options:
  • Check balance
  • Deposit money
  • Withdraw money
  • Exit
• The checkBalance() function displays the current balance.
• The deposit() function allows users to deposit money, updating the balance and logging the transaction.
• The withdraw() function enables users to withdraw money, ensuring the balance is sufficient.
• All transactions are recorded in transactions.txt.

Real-World Examples

• Real ATM transactions: Banks deploy similar logic in ATM machines, integrating database connectivity.
• Data management: In real-world banking applications, account details are stored in a centralized database, and transactions are logged for security purposes.
• Security protocols: Unlike this simple simulation, actual banking software enforces strict security measures.

Security and Error Handling

• In real banking systems, an incorrect PIN attempt would end the session and could temporarily lock the account.
• Additional security layers, such as two-factor authentication (2FA) and biometric scans, are often implemented.
• Banks use transaction logging to detect fraud. If unusual withdrawal patterns are observed, the account may be flagged for review.
• Implementing fraud detection in this ATM simulator would be an important improvement.

Problem-Solving Approaches

Improved Security

• Challenge: Currently, PINs are stored as simple integers.
• Solution: Encrypt stored PINs using a secure hashing algorithm like SHA-256.

Handling Large Transactions

• Challenge: Users may attempt to withdraw more than their available balance.
• Solution: Implement an overdraft protection feature or notify users of a low balance.

Expanded ATM Features

• Challenge: The current program lacks account management.
• Solution: Store multiple balances and accounts in a text file or database for better user management.

Thank you for reading! I hope you learned something valuable. See you next time!