C++ is a general-purpose programming language that supports both procedural and object-oriented programming. It is an extension of C with features like classes, objects, inheritance, and polymorphism.
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C Plus Plus Interview Questions
1. What is C++?
2. What are the key features of C++?
- Object-Oriented
- Faster than most high-level languages
- Supports OOP concepts (Encapsulation, Inheritance, Polymorphism)
- Rich Standard Template Library (STL)
- Memory management using pointers
3. What is the difference between C and C++?
C is procedural, while C++ supports both procedural and object-oriented programming (OOP). C++ also supports features like classes, objects, and function overloading.
4. What is a class and an object?
- Class: Blueprint or template.
- Object: Real-world instance of a class.
class Car {
public:
void drive() { cout << "Driving"; }
};
Car myCar;
MyCar.drive(); 5. What is a constructor?
A constructor is a special function that runs when an object is created. It initializes the object.
class Car {
public:
Car() { cout << "Car created"; }
}; 6. What is a destructor?
A destructor runs when an object is destroyed. Used to release resources like memory or files.
~Car() {
cout << "Car destroyed";
} 7. What is function overloading?
Function with the same name but different parameters.
void show(int a); Void show(double b);
8. What is operator overloading?
Giving new meaning to existing operators like + or ==.
class A {
public:
int x;
A(int val) : x(val) {}
A operator+(A obj) {
return A(x + obj.x);
}
}; 9. What is inheritance?
One class (child) inherits features of another class (parent).
class Animal {
public:
void sound() { cout << "Some sound"; }
};
Class Dog : public Animal {}; 10. What is polymorphism?
"Many forms" – same function behaves differently in different classes (runtime and compile-time).
11. What is a virtual function?
Allows function overriding in inheritance for runtime polymorphism.
class Base {
public:
virtual void show() { cout << "Base"; }
};
class Derived : public Base {
public:
void show() override { cout << "Derived"; }
}; 12. What is the use of this pointer?
this is a pointer that refers to the current object in a class.
13. What is a smart pointer (C++11)?
Automatically manages memory. Types:
- unique_ptr
- shared_ptr
- weak_ptr
#include <memory> Std::unique_ptr<int> ptr(new int(10));
14. What is the difference between new and malloc()?
new calls constructor, supports OOP, type-safe.
malloc() doesn’t call constructor and is from C.
15. What is a template?
Used to write generic functions or classes.
template <typename T>
T add(T a, T b) {
return a + b;
} 16. What is the Standard Template Library (STL)?
Ready-made templates like:
- Vector – Dynamic array
- Map – Key-value
- Set – Unique values
- Stack/Queue – Data structures
17. What is the difference between struct and class in C++?
In C++:
- struct: Members are public by default
- class: Members are private by default
18. What is nullptr (C++11)?
It replaces NULL. It is type-safe.
int* p = nullptr;
19. What is lambda expression (C++11)?
Inline anonymous function.
auto add = [](int a, int b) { return a + b; };
Cout << add(3, 4); // Outputs 7 20. What are move semantics and rvalue references (C++11)?
Used to avoid unnecessary copying and improve performance.
std::string a = "hello"; Std::string b = std::move(a); // Moves instead of copying