ATM machine program in c++ using functions

#include <iostream>
#include <string>

using namespace std;

// Function to handle user login
bool login() {
    string username, password;

    cout << "Enter username: ";
    cin >> username;
    cout << "Enter password: ";
    cin >> password;

    // Verify username and password against a database or file
    // Return true if login is successful, false otherwise
    if(username=="admin" && password=="password")
      return true;
    else
      return false;
}

// Function to check account balance
void check_balance() {
    // Get account balance from a database or file
    int balance = 1000;
    cout << "Your current balance is: $" << balance << endl;
}

// Function to handle money withdrawal
void withdraw() {
    int amount;
    cout << "Enter amount to withdraw: $";
    cin >> amount;

    // Check if the entered amount is valid and there are sufficient funds
    if (amount > 0 && amount <= 1000) {
        // Update account balance in a database or file
        cout << "Please collect your cash." << endl;
        cout << "Your current balance is: $" << (1000-amount) << endl;
    } else {
        cout << "Invalid amount entered." << endl;
    }
}

// Function to handle money deposit
void deposit() {
    int amount;
    cout << "Enter amount to deposit: $";
    cin >> amount;

    // Check if the entered amount is valid
    if (amount > 0) {
        // Update account balance in a database or file
        cout << "Deposit accepted." << endl;
        cout << "Your current balance is: $" << (amount+1000) << endl;
    } else {
        cout << "Invalid amount entered." << endl;
    }
}

// Function to handle changing the ATM pin
void change_pin() {
    int current_pin, new_pin;

    cout << "Enter current pin: ";
    cin >> current_pin;
    cout << "Enter new pin: ";
    cin >> new_pin;

    // Verify current pin against a database or file
    // Update pin in a database or file if current pin is correct
    if (current_pin == 1234) {
        cout << "Pin changed successfully." << endl;
    } else {
        cout << "Incorrect pin entered." << endl;
    }
}

// Function to handle viewing transaction history
void transaction_history() {
    // Retrieve transaction history from a database or file
    cout << "Transaction history:" << endl;
    cout << "Date \t\t Amount \t\t Balance" << endl;
    cout << "01/01/2022 \t $100 \t\t $900" << endl;
    cout << "01/02/2022 \t $50 \t\t $850" << endl;
}