Access Modifiers

Overview

Access modifiers control who can see and modify class members. They enforce Encapsulation.

Syntax

cpp

class Security {
private:
    int secretKey; // Only accessible inside this class

protected:
    int accessLevel; // Accessible here AND in derived classes

public:
    string username; // Accessible from anywhere
};

Common Pitfalls

Making everything `public`. This completely defeats the purpose of classes and object-oriented design.

Interview Tips

By default, all members of a `class` in C++ are `private`. In a `struct`, all members are `public` by default.

Real-World Example

Using private variables to prevent external tampering.

example

cpp

#include <iostream>
using namespace std;

class BankAccount {
private:
    double balance = 0; // Hidden from outside world

public:
    void deposit(double amount) {
        if (amount > 0) balance += amount;
    }
    double getBalance() {
        return balance;
    }
};

int main() {
    BankAccount acc;
    // acc.balance = 1000000; // ERROR: balance is private!
    acc.deposit(50);
    cout << acc.getBalance();
    return 0;
}

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