Protected Access Specifier in C++

 

1️⃣ What is the protected Access Specifier?

In C++, the protected access specifier is used in classes to restrict access to members. It allows:

• Access within the same class.
• Access in derived (child) classes.
• ❌ Not accessible outside the class (unlike public).

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2️⃣ Syntax of protected Access Specifier

class Base {
protected: 
    int protectedVar;  // Accessible in derived class
};

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3️⃣ Example: Using protected in Inheritance

#include <iostream>
using namespace std;

// Base Class
class Parent {
protected:
    int protectedVar; // Protected member

public:
    Parent(int val) {
        protectedVar = val;
    }

    void showValue() {
        cout << "Protected Variable: " << protectedVar << endl;
    }
};

// Derived Class
class Child : public Parent {
public:
    Child(int val) : Parent(val) {}

    void modifyValue(int newVal) {
        protectedVar = newVal;  // Allowed because it is protected
    }
};

int main() {
    Child obj(100);
    obj.showValue();  // ✅ Allowed: Public function of Base
    obj.modifyValue(200);
    obj.showValue();
    
    // obj.protectedVar = 300; ❌ ERROR: Cannot access protected member outside the class
    return 0;
}

🔹 Output

Protected Variable: 100
Protected Variable: 200

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4️⃣ Key Differences: private vs protected vs public

Access Modifier	Accessible in Same Class	Accessible in Derived Class	Accessible Outside Class
private	✅ Yes	❌ No	❌ No
protected	✅ Yes	✅ Yes	❌ No
public	✅ Yes	✅ Yes	✅ Yes

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5️⃣ When to Use protected?

🔹 When you want derived classes to access a member, but not external code.
🔹 Useful in inheritance to share data between base and derived classes.
🔹 Helps enforce encapsulation while allowing subclass flexibility.

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