Object Oriented Programming — One Question at a Time

Practise 150 Object-Oriented Programming multiple-choice questions covering classes, objects, constructors, inheritance, polymorphism, C++ templates, exceptions and smart pointers. Work through one question at a time, check the correct answer with an explanation, and select Next Question to continue. This is self-paced practice without automatic scoring.

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Practice Set 1 · Question 1 of 150

Question 1. In object-oriented programming, what is a class?

A hardware register
A compiler error
A blueprint defining data and behaviour
A single running process

Show Answer and Explanation

Correct answer: C. A blueprint defining data and behaviour

A class specifies an object’s attributes and operations.

Object Oriented Programming — One Question at a Time

Object Oriented Programming — One Question at a Time

Question 1. In object-oriented programming, what is a class?

Question 2. What is an object?

Question 3. Which OOP principle bundles data and related methods together?

Question 4. In C++, which access specifier usually makes a member accessible only inside its class and friends?

Question 5. A class Employee stores name and salary. Which is an example of an instance?

Question 6. What is a constructor used for?

Question 7. In C++, a class destructor is named using which prefix?

Question 8. What is true of a static data member in C++?

Question 9. In a C++ const member function, what is generally disallowed?

Question 10. When is a local C++ object’s destructor normally called?

Question 11. What distinguishes function overloading in C++?

Question 12. What relationship is typically represented by composition?

Question 13. Which relation is best described as ‘is-a’?

Question 14. Which example most naturally illustrates aggregation?

Question 15. In C++, what can operator overloading do?

Question 16. Which access specifier lets derived classes access a C++ base-class member but normally restricts unrelated code?

Question 17. What is runtime polymorphism in C++ usually achieved through?

Question 18. What is the purpose of a pure virtual function in C++?

Question 19. If Dog publicly derives from Animal, which is generally an acceptable substitution?

Question 20. What does an abstract class in C++ prohibit?

Question 21. What is a C++ function template?

Question 22. Which standard C++ container provides contiguous dynamic storage of elements?

Question 23. For a std::vector<int> v = {2,4,6}, what does v.size() return?

Question 24. What is the main idea of generic programming?

Question 25. What is the role of a try block in C++ exception handling?

Question 26. Which keyword explicitly signals an exception in C++?

Question 27. What does serialization generally mean?

Question 28. Why should input from a serialized file be validated before reconstructing an object?

Question 29. What is the main purpose of a catch block?

Question 30. Which principle best supports robust exception handling?

Question 31. A C++ struct differs from a class by default in which way?

Question 32. In C++, what is printed by: class C {public: int x=4;}; C a; C b=a; b.x=9; std::cout<<a.x; ?

Question 33. Which initialization invokes a C++ copy constructor?

Question 34. For a member object owned by another C++ object, which is destroyed first when the outer object is destroyed?

Question 35. Which feature permits initialization of a const data member in C++?

Question 36. If class D publicly inherits B, how are public B members generally accessed through D?

Question 37. A protected base member under private inheritance becomes what access in the derived class?

Question 38. Which mechanism addresses repeated virtual base subobjects in diamond inheritance?

Question 39. What happens if a derived class has a function with the same name as a base-class overload set?

Question 40. Which keyword explicitly disallows further overriding of a virtual function in C++?

Question 41. For virtual void f() and a base reference bound to a derived object, which implementation is invoked?

Question 42. What does override help the C++ compiler verify?

Question 43. Why should a C++ base class intended for polymorphic deletion normally have a virtual destructor?

Question 44. In C++, what is object slicing?

Question 45. Can a C++ abstract class define non-pure member functions?

Question 46. Which declarations are valid C++ function overloads?

Question 47. What is the purpose of an explicit single-argument constructor?

Question 48. What does std::vector::push_back normally do?

Question 49. For std::vector<int> v{8,3,5}; what is v.at(1)?

Question 50. What can happen when std::vector reallocates due to growth?

Question 51. What does a catch(const std::exception& e) handler avoid compared with catch by value?

Question 52. What is the role of noexcept on a function declaration?

Question 53. Which data should normally be included in serialized objects?

Question 54. In C++, what does this print? int x=4; int& r=x; r=9; std::cout<<x;

Question 55. A class owns a dynamically allocated buffer. Which special member is used when an existing object is assigned from another existing object by copy?

Question 56. What is printed? class A {public: static int f(){return 6;}}; std::cout<<A::f();

Question 57. What is printed? struct B {virtual int f(){return 1;}}; struct D:B {int f() override {return 5;}}; D d; B& b=d; std::cout<<b.f();

Question 58. What is printed? struct C {int n=3; int get() const {return n;}}; const C c; std::cout<<c.get();

Question 59. What is printed? std::vector<int> v{1,2}; v.push_back(3); std::cout<<v.size();

Question 60. What is printed? struct X {X(int v):n(v){} int n;}; X a(8); std::cout<<a.n;

Question 61. What does this print? int n=3; auto f=[n](){return n+2;}; n=10; std::cout<<f();

Question 62. Which C++ rule applies to the order of non-static data-member initialization?

Question 63. What does the C++ keyword delete mean in Widget(const Widget&)=delete?

Question 64. Which class is automatically noncopyable because it owns a std::unique_ptr member (unless custom copy support is supplied)?

Question 65. What is the main benefit of std::unique_ptr?

Question 66. Which pair is required for overriding a C++ virtual function?

Question 67. A derived object is accessed through a base pointer. Calling a non-virtual method normally selects which implementation?

Question 68. In C++, which keyword specifies that a virtual function cannot be overridden further?

Question 69. Which class design best models a Car containing and owning its Engine value member?

Question 70. When might aggregation be preferable to composition?

Question 71. Which declaration is a simple C++ function template?

Question 72. For std::vector<int> v{10,20,30}, what does v.at(3) do?

Question 73. Which C++ construct automatically releases owned resources if an exception unwinds the stack?

Question 74. What happens if an exception escapes a noexcept function?

Question 75. Which handler is generally preferable for standard exceptions?

Question 76. Why is serializing a raw pointer’s numerical address generally unsuitable for persistent data?

Question 77. For repeated insertion at the back and indexed random access, which STL container is often a good starting choice?

Question 78. Why should a class expose a small stable public interface?