C++ Access Specifiers

🔐 C++ Access Specifiers

Access specifiers in C++ control where class members (data and methods) can be accessed.
They are essential for encapsulation and data security in Object-Oriented Programming.

🔹 1. Types of Access Specifiers

C++ provides three access specifiers:

Access Specifier Accessibility
public Accessible from anywhere
private Accessible only inside the class
protected Accessible inside class and derived (child) classes

🔹 2. public Access Specifier

Members declared as public can be accessed from outside the class.

class Student {
public:
int id;
string name;
};int main() {
Student s;
s.id = 101; // allowed
s.name = “Amit”; // allowed
}

🔹 3. private Access Specifier

Members declared as private are not accessible outside the class.

class Account {
private:
int balance;public:
void setBalance(int b) {
balance = b;
}

int getBalance() {
return balance;
}
};

int main() {
Account a;
// a.balance = 5000; // ❌ error
a.setBalance(5000); // ✔ allowed
}

✔ Most secure
✔ Default access specifier in a class

🔹 4. protected Access Specifier

protected members are:

  • Accessible inside the class

  • Accessible in derived classes

  • Not accessible through objects

class Parent {
protected:
int x;
};class Child : public Parent {
public:
void setX(int val) {
x = val; // allowed
}
};

🔹 5. Default Access Specifiers

Keyword Default Access
class private
struct public
struct Demo {
int x; // public by default
};

🔹 6. Access Specifiers with Inheritance

class Base {
public:
int a;
protected:
int b;
private:
int c;
};
Member Accessible in Derived Class
a (public) ✔
b (protected) ✔
c (private) ❌

🔹 7. Real-Life Example

class ATM {
private:
int pin;public:
void setPin(int p) {
pin = p;
}

bool validate(int input) {
return pin == input;
}
};

✔ User cannot directly access pin
✔ Secure design

❌ Common Mistakes

class Test {
int x; // private by default
};int main() {
Test t;
// t.x = 10; // ❌ error
}

📌 Summary

  • Access specifiers control visibility

  • public → accessible everywhere

  • private → accessible only inside class

  • protected → class + derived classes

  • Default: class → private, struct → public

  • Essential for encapsulation and security

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