Understanding Access Modifiers in C++

Access modifiers in C++ are keywords that define the accessibility of classes and their members (attributes and methods). Grasping these modifiers is essential for achieving encapsulation, a fundamental principle of object-oriented programming.

Key Access Modifiers

1. Public
   • Members declared as public can be accessed from anywhere in the program.
   • Example:
2. Private
   • Members declared as private can only be accessed within the class itself and are not accessible from outside.
   • Example:
3. Protected
   • Members declared as protected can be accessed within the class and by derived classes (subclasses), but they are not accessible from outside the class.
   • Example:

class Base {
protected:
    int protectedVar;
};

class Derived : public Base {
public:
    void accessProtectedVar() {
        protectedVar = 10; // Accessible here
    }
};

class MyClass {
private:
    int privateVar;
    void privateMethod() {
        // Method implementation
    }
};

class MyClass {
public:
    int publicVar;
    void publicMethod() {
        // Method implementation
    }
};

Summary of Access Modifier Behavior

• Public Members: Accessible from anywhere.
• Private Members: Accessible only within the class.
• Protected Members: Accessible within the class and its derived classes.

Example of All Access Modifiers

#include <iostream>
using namespace std;

class Example {
public:
    int publicVar; // Public member
private:
    int privateVar; // Private member
protected:
    int protectedVar; // Protected member

public:
    Example() : publicVar(1), privateVar(2), protectedVar(3) {}

    void show() {
        cout << "Public: " << publicVar << ", Private: " << privateVar << ", Protected: " << protectedVar << endl;
    }
};

int main() {
    Example obj;
    obj.publicVar = 10; // Accessible
    // obj.privateVar = 20; // Not accessible (will cause an error)
    obj.show(); // Outputs: Public: 10, Private: 2, Protected: 3
    return 0;
}

Conclusion

Understanding access modifiers is essential for controlling how data is accessed and modified in your classes. By properly utilizing public, private, and protected, you can create robust and secure C++ programs that adhere to best practices in object-oriented programming.