Encapsulation is the process of bundling data (variables) and the methods that operate on them into a single unit (Class). It also involves hiding internal details using access specifiers (private, protected).

Always! Use encapsulation to protect your data from being modified directly by external code and to enforce valid states (e.g., using setAge() with validation).

• Member Access: $O(1)$.

cpp Standard
class Employee {
private:
    int salary; // Hidden

public:
    void setSalary(int s) {
        if (s > 0) salary = s; // Validation
    }
    int getSalary() { return salary; }
};

• Making all members public (defeats the purpose).
• Not providing getters/setters for data that should be read/modified.
• Exposing internal implementation details in the public interface.