Summary:
A robust, console-based simulation of an Automated Teller Machine. This project demonstrates the core pillars of Object-Oriented Programming (Encapsulation, Abstraction, and Data Integrity) by managing secure user sessions, balance persistence, and transaction validation.
Learning Objectives:
Encapsulation: Protecting sensitive data (PIN, Balance) using private access modifiers.
Input Validation: Implementing robust error handling for non-numeric inputs using <limits>.
Formatted Output: Using <iomanip> to ensure monetary values are displayed with two decimal places.
State Management: Handling the logic flow between authentication, transaction, and exit states.
The Source Code
This code is optimized for the MinGW compiler. It includes pre-emptive clearing of the input buffer to prevent common "looping" bugs in the Code::Blocks console environment.
#include <iostream>
#include <string>
#include <iomanip>
#include <limits>
using namespace std;
// Class representing the Bank Account / ATM Logic
class ATM {
private:
string accountHolder;
int pin;
double balance;
public:
// Constructor
ATM(string name, int p, double initialCap)
: accountHolder(name), pin(p), balance(initialCap) {}
// Validation
bool authenticate(int enteredPin) {
return enteredPin == pin;
}
// Transactions
void deposit(double amount) {
if (amount > 0) {
balance += amount;
cout << "\n[Success] Deposit of $" << fixed << setprecision(2) << amount << " processed.";
}
}
bool withdraw(double amount) {
if (amount > balance) {
cout << "\n[Error] Insufficient funds. Available: $" << fixed << setprecision(2) << balance;
return false;
} else if (amount <= 0) {
cout << "\n[Error] Invalid amount.";
return false;
}
balance -= amount;
cout << "\n[Success] Please collect your $" << fixed << setprecision(2) << amount;
return true;
}
double getBalance() const {
return balance;
}
string getName() const {
return accountHolder;
}
};
// Helper function to handle non-numeric input errors in MinGW/Code::Blocks
void clearBuffer() {
cin.clear();
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
int main() {
ATM myAccount("Academic User", 1234, 1000.00);
int enteredPin, choice;
double amount;
bool isAuthenticated = false;
cout << "--- WELCOME TO THE C++ ACADEMIC BANK ---" << endl;
// Login Loop
while (!isAuthenticated) {
cout << "Enter 4-Digit PIN: ";
if (!(cin >> enteredPin)) {
cout << "Invalid input type. Please enter numbers only." << endl;
clearBuffer();
continue;
}
if (myAccount.authenticate(enteredPin)) {
isAuthenticated = true;
cout << "\nAccess Granted. Welcome, " << myAccount.getName() << "!" << endl;
} else {
cout << "Incorrect PIN. Try again." << endl;
}
}
// Menu Loop
do {
cout << "\n\n--- MAIN MENU ---" << endl;
cout << "1. Check Balance" << endl;
cout << "2. Deposit" << endl;
cout << "3. Withdraw" << endl;
cout << "4. Exit" << endl;
cout << "Selection: ";
if (!(cin >> choice)) {
cout << "Error: Numeric input required." << endl;
clearBuffer();
choice = 0; // Reset
continue;
}
switch (choice) {
case 1:
cout << "Current Balance: $" << fixed << setprecision(2) << myAccount.getBalance();
break;
case 2:
cout << "Enter deposit amount: ";
cin >> amount;
myAccount.deposit(amount);
break;
case 3:
cout << "Enter withdrawal amount: ";
cin >> amount;
myAccount.withdraw(amount);
break;
case 4:
cout << "Thank you for using our ATM. Goodbye!" << endl;
break;
default:
cout << "Invalid selection." << endl;
}
} while (choice != 4);
return 0;
} |
Execution Trace (Sample Session)
--- WELCOME TO THE C++ ACADEMIC BANK ---
Enter 4-Digit PIN: 1234
Access Granted. Welcome, Academic User!
--- MAIN MENU ---
1. Check Balance
2. Deposit
3. Withdraw
4. Exit
Selection: 1
Current Balance: $1000.00
--- MAIN MENU ---
Selection: 3
Enter withdrawal amount: 200
[Success] Please collect your $200.00
--- MAIN MENU ---
Selection: 2
Enter deposit amount: -50
[Error] Invalid amount. |
Academic "Learning Corner"
The Input Fail-Safe: When using cin >> choice, if a user enters a character like 'A', the input stream enters a "fail state." Without cin.clear() and cin.ignore(), the program would enter an infinite loop because the 'A' remains in the buffer.
The fixed and setprecision Manipulators: In financial software, precision is critical. By default, C++ might show 1000.5 as 1000.5. Using fixed coupled with setprecision(2) forces the output to 1000.50, meeting standard accounting formats.
MinGW Compatibility: We use std::endl and flush the buffer frequently to ensure the Code::Blocks "Logs & Others" window displays output in real-time, as some versions of the MinGW console are heavily buffered.
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