C++ Inheritance Access

C++ Tutorial

🔐 C++ Inheritance Access (Access Modes)

Inheritance access in C++ defines how the members of a base class are inherited into a derived class.
It depends on two things:

  1. Access specifiers of base class members (public, protected, private)

  2. Inheritance mode (public, protected, private)

🔹 1. Base Class Member Access


Member Accessible in Derived Class
public ✔
protected ✔
private ❌

👉 private members are never inherited directly

🔹 2. Inheritance Modes

🔹 3. Public Inheritance (Most Common)

Base Member Becomes in Derived
public public
protected protected
private not accessible

✔ Represents is-a relationship

🔹 4. Protected Inheritance

Base Member Becomes in Derived
public protected
protected protected
private not accessible

✔ Limits outside access
❌ Not commonly used

🔹 5. Private Inheritance

Base Member Becomes in Derived
public private
protected private
private not accessible

✔ Used for has-a implementation
❌ No polymorphism

🔹 6. Accessing Inherited Members


 

🔹 7. Access from Object (Important)

Derived d;
// d.x; // ❌ protected not accessible

Protected members are accessible inside class, not via object.

🔹 8. Real-World Example


 

✔ Car is a Vehicle
✔ Speed not accessible directly by user

🔹 9. Quick Summary Table

Inheritance public protected private
public public protected ❌
protected protected protected ❌
private private private ❌

❌ Common Mistakes

class Child : private Parent {};

➡ Breaks is-a relationship unintentionally.

📌 Summary

  • Inheritance access controls visibility of base members

  • Public inheritance preserves access levels

  • Protected/private inheritance restrict access

  • private members are never inherited

  • Use public inheritance for polymorphism

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