Day 50: The Ultimate Bank System (Mini project)

🎉 DAY 50: HALF CENTURY 🎉

From "Hello World" to "Bank System Architect".

50 Days of Code. No Breaks. Pure Grind.

🏦 Project: The Ultimate Bank System

Today, we are not learning a new topic. We are combining Everything we have learned so far into one powerful software.

We will build a banking system where:

• Encapsulation: Customer data (Balance) is secure.
• Inheritance: We have different account types (Savings, Current) inheriting from a base Account.
• Polymorphism: The withdraw() function works differently for Savings (Strict) vs Current (Overdraft allowed).

---

📐 The Architecture (Logic)

Before coding, a good developer designs the system.

1. Class: BankAccount (Parent)

• Properties: AccountNumber, Name, Balance (Protected).
• Functions: deposit(), display().

2. Class: SavingsAccount (Child)

• Rule: Cannot withdraw if balance falls below ₹500.

3. Class: CurrentAccount (Child)

• Rule: Can withdraw extra money (Overdraft) up to ₹1000.

---

💻 The Source Code

Copy this code into your IDE to run the system.

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

// ------------------------------------------
// 1. ABSTRACT BASE CLASS (The Blueprint)
// ------------------------------------------
class BankAccount {
    protected:
        int accNum;
        string name;
        double balance;

    public:
        // Constructor
        BankAccount(int a, string n, double b) {
            accNum = a;
            name = n;
            balance = b;
        }

        // Common Function: Deposit
        void deposit(double amount) {
            balance += amount;
            cout << "✅ " << amount << " Deposited. New Balance: " << balance << endl;
        }

        // Virtual Function (Polymorphism)
        // We let the children decide how to withdraw
        virtual void withdraw(double amount) = 0; 

        // Display Info
        void display() {
            cout << "\n-----------------------" << endl;
            cout << "👤 Account Holder: " << name << endl;
            cout << "🔢 Account No: " << accNum << endl;
            cout << "💰 Balance: ₹" << balance << endl;
            cout << "-----------------------" << endl;
        }
};

// ------------------------------------------
// 2. SAVINGS ACCOUNT (Strict Rules)
// ------------------------------------------
class SavingsAccount : public BankAccount {
    public:
        // Constructor passing data to Parent
        SavingsAccount(int a, string n, double b) : BankAccount(a, n, b) {}

        // Overriding Withdraw Logic
        void withdraw(double amount) {
            if (balance - amount < 500) {
                cout << "❌ Transaction Failed: Minimum Balance (₹500) rule!" << endl;
            } else {
                balance -= amount;
                cout << "✅ Withdraw Success: ₹" << amount << endl;
            }
        }
};

// ------------------------------------------
// 3. CURRENT ACCOUNT (Flexible Rules)
// ------------------------------------------
class CurrentAccount : public BankAccount {
    public:
        CurrentAccount(int a, string n, double b) : BankAccount(a, n, b) {}

        void withdraw(double amount) {
            // Allow overdraft of 1000
            if (balance - amount < -1000) {
                cout << "❌ Transaction Failed: Overdraft Limit Exceeded!" << endl;
            } else {
                balance -= amount;
                cout << "✅ Withdraw Success: ₹" << amount << endl;
            }
        }
};

// ------------------------------------------
// MAIN FUNCTION (The Driver)
// ------------------------------------------
int main() {
    cout << "=== 🏦 WELCOME TO SAHIL BANK SYSTEM 🏦 ===\n" << endl;

    // 1. Creating a Savings Account for Sahil
    cout << "--- Creating Savings Account ---" << endl;
    SavingsAccount s1(101, "Sahil Tiwari", 2000);
    s1.display();

    s1.deposit(500);       // Add Money
    s1.withdraw(2100);     // Try to empty account (Should Fail due to min balance)
    s1.withdraw(1000);     // Valid Withdraw

    // 2. Creating a Current Account for Business
    cout << "\n--- Creating Current Account ---" << endl;
    CurrentAccount c1(102, "Sahil Tech Solutions", 5000);
    c1.display();

    c1.withdraw(5500);     // Withdraw more than balance (Should Pass due to Overdraft)
    c1.display();

    return 0;
}

---

📟 The Final Output

When you compile and run this code, here is what the console looks like:

=== 🏦 WELCOME TO SAHIL BANK SYSTEM 🏦 ===

--- Creating Savings Account ---

-----------------------

👤 Account Holder: Sahil Tiwari

🔢 Account No: 101

💰 Balance: ₹2000

-----------------------

✅ 500 Deposited. New Balance: 2500

❌ Transaction Failed: Minimum Balance (₹500) rule!

✅ Withdraw Success: ₹1000

--- Creating Current Account ---

-----------------------

👤 Account Holder: Sahil Tech Solutions

🔢 Account No: 102

💰 Balance: ₹5000

-----------------------

✅ Withdraw Success: ₹5500

-----------------------

👤 Account Holder: Sahil Tech Solutions

🔢 Account No: 102

💰 Balance: ₹-500

-----------------------

---

🚀 50 Days Complete!

We started with int a = 10; and today we built a Banking System using Polymorphism. This is the power of consistency.

Next Mission (Day 51-100): We dive into Advanced Data Structures (Linked Lists, Stacks, Queues) and Competitive Programming. The real game begins now.