Object-Oriented Programming (OOP) in C++ revolutionizes software design by organizing code around data (objects) rather than relying solely on functions and logic. Introduced by Bjarne Stroustrup as “C with Classes,” C++ fully supports the four fundamental pillars of OOP: encapsulation, abstraction, inheritance, and polymorphism. By utilizing access specifiers (public, private, protected), C++ enforces strict data hiding and memory security. Advanced features like virtual functions, abstract classes, and multiple inheritance give C++ immense architectural power and flexibility. Mastering C++ OOP principles is critical for building scalable, maintainable systems, preventing memory leaks through virtual destructors, and passing technical software engineering interviews.
1. What is OOP?
Correct Answer: a) A programming paradigm based on objects
Explanation:
OOP organizes software around objects that combine data and behavior.
2. What is a class in C++?
Correct Answer: b) A blueprint for objects
Explanation:
A class defines the data and operations that its objects will have.
3. What is an object in C++?
Correct Answer: c) An instance of a class
Explanation:
Objects are concrete instances created from a class.
4. What is encapsulation?
Correct Answer: d) Bundling data and methods together
Explanation:
Encapsulation keeps related data and behavior inside a class and controls access.
5. Which access specifier is commonly used for data hiding?
Correct Answer: a) private
Explanation:
Private members are not directly accessible from outside the class.
6. What is abstraction?
Correct Answer: b) Exposing only essential features
Explanation:
Abstraction hides implementation details and presents a clear interface.
7. What is inheritance?
Correct Answer: c) Deriving new classes from existing classes
Explanation:
Inheritance lets a new class reuse and extend an existing class.
8. What is polymorphism?
Correct Answer: d) The same interface with different behavior
Explanation:
Polymorphism allows different classes to respond to the same interface.
9. Which keyword is used to define a class in C++?
Correct Answer: a) class
Explanation:
The class keyword introduces a class definition.
10. What is the default access specifier in a C++ class?
Correct Answer: b) private
Explanation:
Class members are private by default unless specified otherwise.
11. What is the default access specifier in a C++ struct?
Correct Answer: c) public
Explanation:
Struct members are public by default unless specified otherwise.
12. Which specifier restricts access to members within the same class only?
Correct Answer: d) private
Explanation:
Private members can only be accessed by members and friends of that class.
13. Which access specifier allows access in derived classes?
Correct Answer: a) protected
Explanation:
Protected members are accessible in the class and its derived classes.
14. What is true about a member function defined inside a class body?
Correct Answer: b) It is inline by default
Explanation:
Member functions defined inside the class are implicitly inline.
15. Which statement creates an object of class MyClass?
Correct Answer: c) MyClass obj;
Explanation:
A variable declaration using the class name creates an object.
16. What is the dot operator used for?
Correct Answer: d) Accessing object members
Explanation:
The dot operator accesses members through an object.
17. Which operator allocates dynamic memory in C++?
Correct Answer: a) new
Explanation:
new allocates memory and constructs objects in C++.
18. Which operator releases memory allocated by new?
Correct Answer: b) delete
Explanation:
delete destroys objects and releases memory allocated by new.
19. What is the name of a constructor?
Correct Answer: c) The same as the class name
Explanation:
Constructors have the same name as their class.
20. What is the return type of a constructor?
Correct Answer: d) It has no return type
Explanation:
Constructors do not specify a return type.
21. When is a constructor called?
Correct Answer: a) When an object is created
Explanation:
Constructors initialize objects during creation.
22. What is a default constructor?
Correct Answer: b) A constructor that can be called with no arguments
Explanation:
A default constructor can create an object without providing arguments.
23. What does a copy constructor copy?
Correct Answer: c) An object of the same class
Explanation:
A copy constructor initializes a new object from an existing object.
24. What is the name of a destructor for class MyClass?
Correct Answer: d) ~MyClass
Explanation:
Destructors use the class name prefixed with a tilde.
25. When is a destructor called?
Correct Answer: a) When an object is destroyed
Explanation:
Destructors clean up resources when object lifetime ends.
26. Can a class have multiple constructors?
Correct Answer: b) Yes
Explanation:
Constructors can be overloaded with different parameter lists.
27. What is constructor overloading?
Correct Answer: c) Providing multiple constructors with different parameters
Explanation:
Overloading allows different ways to initialize objects.
28. What is a member initializer list used for?
Correct Answer: d) Initializing members before the constructor body runs
Explanation:
Initializer lists initialize members directly during construction.
29. Which member usually must be initialized in a constructor initializer list?
Correct Answer: a) A non-static const data member
Explanation:
Const non-static data members need initialization before the constructor body.
30. What does the explicit keyword prevent for a constructor?
Correct Answer: b) Implicit conversion from the constructor argument
Explanation:
explicit stops unintended implicit conversions during object creation.
31. What is true about an explicit constructor?
Correct Answer: c) It requires direct initialization for that conversion
Explanation:
explicit constructors are used for direct initialization, not implicit conversion.
32. What does MyClass obj; invoke if available?
Correct Answer: d) Default constructor
Explanation:
Creating an object without arguments uses a default constructor.
33. What does MyClass obj2(obj1); invoke?
Correct Answer: a) Copy constructor
Explanation:
Direct initialization from another object uses the copy constructor.
34. What does obj2 = obj1; invoke when both objects already exist?
Correct Answer: b) Copy assignment operator
Explanation:
Assigning to an existing object uses copy assignment.
35. Which function is part of the Rule of Three?
Correct Answer: c) Copy assignment operator
Explanation:
The Rule of Three includes destructor, copy constructor, and copy assignment.
36. Which function is added in the Rule of Five?
Correct Answer: d) Move assignment operator
Explanation:
The Rule of Five adds move constructor and move assignment.
37. If no user-defined constructor exists, what may the compiler generate?
Correct Answer: a) A default constructor
Explanation:
The compiler can implicitly declare a default constructor when needed.
38. If no destructor is declared, what may the compiler generate?
Correct Answer: b) A default destructor
Explanation:
The compiler provides an implicit destructor if none is declared.
39. What is the this pointer?
Correct Answer: c) A pointer to the current object
Explanation:
Inside member functions, this points to the object on which the function is called.
40. Can a static member function access the this pointer?
Correct Answer: d) No
Explanation:
Static member functions are not associated with an object instance.
41. What is true about a static data member?
Correct Answer: a) It is shared by all objects of the class
Explanation:
Static data members belong to the class, not to individual objects.
42. How can a static member function be called?
Correct Answer: b) Using the class name
Explanation:
Static member functions can be called without an object.
43. Where is a non-inline static data member usually defined?
Correct Answer: c) Outside the class definition
Explanation:
Static data members typically need a separate definition outside the class.
44. What is true about a const member function?
Correct Answer: d) It promises not to modify non-mutable members
Explanation:
const member functions cannot change non-mutable member variables.
45. What does the mutable keyword allow?
Correct Answer: a) A member to be modified in a const member function
Explanation:
mutable members can change even inside const member functions.
46. What is a friend function?
Correct Answer: b) A non-member function that can access private members
Explanation:
friend functions are granted access to private and protected members.
47. What does a friend class do?
Correct Answer: c) Can access private members of the class that declares it friend
Explanation:
Friendship gives another class access to private and protected members.
48. Which operator cannot be overloaded?
Correct Answer: d) ::
Explanation:
The scope resolution operator cannot be overloaded.
49. Which operator can be overloaded?
Correct Answer: a) +
Explanation:
Arithmetic operators such as + can be overloaded for class types.
50. Which operator cannot be overloaded?
Correct Answer: b) .
Explanation:
The member access operator . cannot be overloaded.
51. How is operator<< usually overloaded for output?
Correct Answer: c) As a non-member or friend function
Explanation:
The left operand is usually ostream, so a non-member is natural.
52. What is a pure virtual function?
Correct Answer: d) A virtual function declared with = 0
Explanation:
A pure virtual function has no required implementation in the base class.
53. What is an abstract class?
Correct Answer: a) A class that cannot be instantiated
Explanation:
Abstract classes define interfaces and cannot create direct objects.
54. What usually makes a class abstract?
Correct Answer: b) At least one pure virtual function
Explanation:
A class with a pure virtual function cannot be instantiated.
55. What does the virtual keyword enable?
Correct Answer: c) Runtime polymorphism
Explanation:
virtual allows derived classes to override functions selected at runtime.
56. What does overriding mean?
Correct Answer: d) Redefining a virtual function in a derived class
Explanation:
An override provides a derived implementation of a base virtual function.
57. Which specifier helps ensure a function overrides a base function?
Correct Answer: a) override
Explanation:
override makes the compiler check that the function overrides a base function.
58. What does final do when applied to a virtual function?
Correct Answer: b) Prevents overriding
Explanation:
A final virtual function cannot be overridden by derived classes.
59. When is a virtual destructor especially important?
Correct Answer: c) When deleting derived objects through base pointers
Explanation:
A virtual destructor ensures the derived destructor runs.
60. What can happen if a base destructor is not virtual when deleting a derived object through a base pointer?
Correct Answer: d) It can cause undefined behavior
Explanation:
Without a virtual destructor, only the base destructor may run.
61. Which mechanism achieves dynamic polymorphism in C++?
Correct Answer: a) Virtual functions
Explanation:
Virtual function dispatch selects implementations at runtime.
62. Which is an example of compile-time polymorphism?
Correct Answer: b) Function overloading or templates
Explanation:
Compile-time polymorphism resolves calls during compilation.
63. What is function overloading?
Correct Answer: c) Using the same function name with different parameters
Explanation:
Overloaded functions differ by parameter types or counts.
64. What does operator overloading change?
Correct Answer: d) Operator behavior for class types
Explanation:
Overloading defines how operators behave for user-defined types.
65. What is true about a derived class?
Correct Answer: a) It can inherit members from a base class
Explanation:
Derived classes extend base classes with new or overridden members.
66. Which syntax shows public inheritance?
Correct Answer: b) class D : public B
Explanation:
C++ uses a colon and access specifier for inheritance.
67. In public inheritance, public base members become what in the derived class?
Correct Answer: c) public
Explanation:
Public inheritance preserves public access for base members.
68. In protected inheritance, public base members become what?
Correct Answer: d) protected
Explanation:
Protected inheritance lowers public base members to protected.
69. In private inheritance, public base members become what?
Correct Answer: a) private
Explanation:
Private inheritance makes inherited members private in the derived class.
70. When is a base class constructor called during derived construction?
Correct Answer: b) Before the derived constructor body
Explanation:
Base subobjects are initialized before derived members and body.
71. When is a base class destructor called during destruction?
Correct Answer: c) After the derived destructor body
Explanation:
Destruction proceeds from derived to base.
72. What is the order of construction in single inheritance?
Correct Answer: d) Base then derived
Explanation:
Base classes are constructed before derived classes.
73. What is the order of destruction in single inheritance?
Correct Answer: a) Derived then base
Explanation:
Derived destructors run before base destructors.
74. What is multiple inheritance?
Correct Answer: b) A class inherits from more than one base class
Explanation:
A derived class can have several direct bases.
75. What causes the diamond problem?
Correct Answer: c) Multiple inheritance paths to the same base class
Explanation:
Two paths to one base can create ambiguity.
76. What helps solve the diamond problem?
Correct Answer: d) Virtual inheritance
Explanation:
Virtual inheritance creates one shared base subobject.
77. In virtual inheritance, what exists for the virtual base?
Correct Answer: a) One shared base subobject
Explanation:
Virtual inheritance avoids duplicated base parts.
78. Which keyword is used for a virtual base class?
Correct Answer: b) virtual
Explanation:
The virtual keyword in the base list enables virtual inheritance.
79. What relationship does composition usually model?
Correct Answer: c) Has-a
Explanation:
Composition means one object contains another.
80. What relationship does inheritance often model?
Correct Answer: d) Is-a
Explanation:
A derived object is a kind of base object.
81. Which is often preferred to reuse behavior without exposing implementation?
Correct Answer: a) Composition
Explanation:
Composition can combine objects while keeping implementation hidden.
82. What is a common C++ interface-like construct?
Correct Answer: b) An abstract class with pure virtual functions
Explanation:
Pure virtual functions define an interface for derived classes.
83. What is a concrete class?
Correct Answer: c) A class that can be instantiated
Explanation:
A concrete class has implementations for all required functions.
84. What does Base* p = new Derived; create?
Correct Answer: d) A base pointer pointing to a Derived object
Explanation:
A base pointer can refer to a derived object.
85. What is needed to call an overridden function through a base pointer?
Correct Answer: a) A virtual function
Explanation:
Virtual dispatch selects the derived implementation.
86. Without virtual, calls through a base pointer use which type?
Correct Answer: b) Static pointer type
Explanation:
Non-virtual calls are resolved using the pointer type.
87. What is static binding?
Correct Answer: c) Compile-time resolution
Explanation:
Static binding decides the function call during compilation.
88. What is dynamic binding?
Correct Answer: d) Runtime resolution
Explanation:
Dynamic binding selects functions while the program runs.
89. What does a virtual table usually contain?
Correct Answer: a) Pointers to virtual functions
Explanation:
The vtable stores addresses of virtual functions for dispatch.
90. What is a vptr?
Correct Answer: b) A pointer in an object to its vtable
Explanation:
Objects with virtual functions often contain a vptr.
91. When is a vptr typically initialized?
Correct Answer: c) During construction
Explanation:
The constructor sets up the object's vptr.
92. Can a constructor be virtual?
Correct Answer: d) No
Explanation:
Constructors cannot be virtual because the object type is being created.
93. Can a destructor be virtual?
Correct Answer: a) Yes
Explanation:
Virtual destructors support safe polymorphic deletion.
94. Can a copy constructor be virtual?
Correct Answer: b) No
Explanation:
Constructors, including copy constructors, cannot be virtual.
95. Can a member function be both static and virtual?
Correct Answer: c) No
Explanation:
Virtual dispatch requires an object, while static functions do not have this.
96. Can a const member function be virtual?
Correct Answer: d) Yes
Explanation:
const member functions can be virtual and overridden.
97. What is object slicing?
Correct Answer: a) Copying only the base part when a derived object is copied as a base value
Explanation:
Value assignment to a base type can lose derived data.
98. How can slicing be avoided?
Correct Answer: b) Using pointers or references
Explanation:
Pointers and references preserve the dynamic type.
99. What does dynamic_cast require for downcasting?
Correct Answer: c) A polymorphic source type
Explanation:
dynamic_cast needs virtual functions for runtime type checking.
100. What does dynamic_cast return if a pointer cast fails?
Correct Answer: d) nullptr
Explanation:
For pointer types, a failed dynamic_cast returns nullptr.
101. Which cast is usually safest for polymorphic downcasting?
Correct Answer: a) dynamic_cast
Explanation:
dynamic_cast checks the actual runtime type.
102. What is true about static_cast downcasting?
Correct Answer: b) It does not check runtime type
Explanation:
static_cast assumes the cast is valid.
103. What does RTTI stand for?
Correct Answer: c) Runtime Type Information
Explanation:
RTTI provides type identity features such as dynamic_cast and typeid.
104. What can typeid provide?
Correct Answer: d) Type information
Explanation:
typeid returns a type_info object describing the type.
105. Which header is needed for typeid?
Correct Answer: a) typeinfo
Explanation:
The typeinfo header defines type_info.
106. What is a class with at least one virtual function called?
Correct Answer: b) Polymorphic
Explanation:
Virtual functions make a class capable of runtime dispatch.
107. What is a class with a pure virtual function called?
Correct Answer: c) Abstract
Explanation:
Pure virtual functions prevent direct instantiation.
108. Can a pure virtual function have a definition?
Correct Answer: d) Yes, separately outside the class
Explanation:
A pure virtual function can still be defined explicitly.
109. Which is the correct syntax for a virtual destructor?
Correct Answer: a) virtual ~Base() { }
Explanation:
The virtual keyword appears before the destructor declaration.
110. Where is the override specifier placed?
Correct Answer: b) After the function declaration in the derived class
Explanation:
override follows the member function declarator.
111. Where can final be used?
Correct Answer: c) After a virtual function or after a class name
Explanation:
final can prevent overriding or inheritance.
112. What does class Derived final mean?
Correct Answer: d) Derived cannot be used as a base class
Explanation:
A final class cannot be inherited.
113. What does a function marked final prevent?
Correct Answer: a) Further overriding
Explanation:
Derived classes cannot override a final virtual function.
114. What can happen if a derived class declares a member with the same name as a base member?
Correct Answer: b) The base member may be hidden
Explanation:
Name hiding can shadow base class members.
115. What is name hiding?
Correct Answer: c) A derived member shadows a base member
Explanation:
The derived declaration can hide same-named base declarations.
116. How can a hidden base member be accessed explicitly?
Correct Answer: d) Using Base::member
Explanation:
Scope resolution selects the base class member.
117. What can a using declaration in a derived class do?
Correct Answer: a) Bring base overloaded functions into scope
Explanation:
using Base::name can prevent hiding of overloads.
118. How are constructors inherited in C++11 and later?
Correct Answer: b) using Base::Base;
Explanation:
A using declaration can inherit base constructors.
119. What is a nested class?
Correct Answer: c) A class defined inside another class
Explanation:
Nested classes are declared within the scope of another class.
120. What is true about a nested class?
Correct Answer: d) It is scoped inside the enclosing class
Explanation:
A nested class name is scoped by its enclosing class.
121. What is a local class?
Correct Answer: a) A class defined inside a function
Explanation:
Local classes are declared within function scope.
122. Can a local class have static data members?
Correct Answer: b) No
Explanation:
Local classes cannot contain static data members.
123. Can a local class define member functions outside the class body?
Correct Answer: c) No
Explanation:
Local class member functions must be defined inside the class.
124. Can a local class have constructors and destructors?
Correct Answer: d) Yes
Explanation:
Local classes may define constructors and destructors inside the class.
125. Can a class be declared without being defined?
Correct Answer: a) Yes, with a forward declaration
Explanation:
class MyClass; declares an incomplete type.
126. What is a forward declaration useful for?
Correct Answer: b) Reducing dependencies and incomplete type usage
Explanation:
Forward declarations can reduce header coupling.
127. What is an incomplete type?
Correct Answer: c) A declared but not defined class
Explanation:
Incomplete types lack a full definition.
128. Can you create an object of an incomplete type?
Correct Answer: d) No
Explanation:
Objects require a complete class definition.
129. Can you declare a pointer to an incomplete type?
Correct Answer: a) Yes
Explanation:
Pointers can refer to incomplete types.
130. What is the PIMPL idiom?
Correct Answer: b) Pointer to implementation to hide details
Explanation:
PIMPL separates interface from implementation.
131. What does RAII stand for?
Correct Answer: c) Resource Acquisition Is Initialization
Explanation:
RAII ties resource management to object lifetime.
132. What does RAII tie resource lifetime to?
Correct Answer: d) Object lifetime
Explanation:
Resources are acquired in constructors and released in destructors.
133. Which is a smart pointer type?
Correct Answer: a) unique_ptr
Explanation:
unique_ptr manages dynamically allocated memory.
134. What kind of ownership does unique_ptr provide?
Correct Answer: b) Exclusive
Explanation:
Only one unique_ptr should own a resource.
135. What does shared_ptr provide?
Correct Answer: c) Reference-counted shared ownership
Explanation:
shared_ptr deletes the object when the last owner is gone.
136. What is weak_ptr?
Correct Answer: d) A non-owning observer
Explanation:
weak_ptr observes shared_ptr without extending ownership.
137. What helps break circular references with shared_ptr?
Correct Answer: a) weak_ptr
Explanation:
weak_ptr avoids increasing the reference count.
138. What does make_shared do?
Correct Answer: b) Creates a shared_ptr efficiently
Explanation:
make_shared allocates the object and control block together.
139. What is move semantics?
Correct Answer: c) Transferring resources from one object to another
Explanation:
Move semantics avoid unnecessary copying.
140. How is an rvalue reference declared?
Correct Answer: d) &&
Explanation:
Rvalue references use double ampersand.
141. What does std::move do?
Correct Answer: a) Casts an object to an rvalue reference
Explanation:
std::move enables move operations but does not move by itself.
142. What does a move constructor do?
Correct Answer: b) Transfers resources from the source object
Explanation:
Move constructors take resources from rvalue sources.
143. What state should a moved-from object usually be in?
Correct Answer: c) Valid but unspecified
Explanation:
Moved-from objects should be safe to destroy or assign.
144. What is a common problem caused by shallow copying?
Correct Answer: d) Double deletion
Explanation:
Two objects may delete the same resource.
145. What does a deep copy do?
Correct Answer: a) Copies owned resources
Explanation:
Deep copying duplicates the underlying resource.
146. What does the copy-and-swap idiom help implement?
Correct Answer: b) Copy assignment safely
Explanation:
It uses a temporary copy and swap to provide strong exception safety.
147. What is a swap member function used for?
Correct Answer: c) Exchanging object states
Explanation:
swap exchanges internals of two objects efficiently.
148. What does noexcept indicate?
Correct Answer: d) The function is not expected to throw
Explanation:
noexcept can enable optimizations and safer move operations.
149. Why mark move operations noexcept?
Correct Answer: a) To enable optimizations and safe container behavior
Explanation:
Containers may prefer noexcept move operations.
150. What is a functor?
Correct Answer: b) A function object
Explanation:
A functor is an object that can be called like a function.
151. What is a lambda expression?
Correct Answer: c) An anonymous function object
Explanation:
Lambdas create callable objects inline.
152. What does an empty lambda capture [] mean?
Correct Answer: d) Capture nothing
Explanation:
An empty capture list uses no local variables.
153. What does [&] capture mean?
Correct Answer: a) Capture by reference
Explanation:
All used local variables are captured by reference.
154. What does [=] capture mean?
Correct Answer: b) Capture by value
Explanation:
All used local variables are copied into the lambda.
155. Can a lambda be stored in std::function?
Correct Answer: c) Yes, if signatures are compatible
Explanation:
std::function can hold callable objects.
156. What is a generic lambda?
Correct Answer: d) A lambda using auto parameters
Explanation:
Generic lambdas accept arguments of deduced types.
157. What is a template?
Correct Answer: a) A generic blueprint for types or functions
Explanation:
Templates allow code parameterized by types.
158. What do templates primarily support?
Correct Answer: b) Compile-time generic programming
Explanation:
Templates generate type-specific code during compilation.
159. Which keyword begins a template definition?
Correct Answer: c) template
Explanation:
The template keyword introduces template parameters.
160. Which is correct class template syntax?
Correct Answer: d) template <typename T> class C { }
Explanation:
Template parameters appear in angle brackets after template.
161. Can templates be overloaded?
Correct Answer: a) Yes
Explanation:
Different template or parameter combinations can be overloaded.
162. What is template specialization?
Correct Answer: b) A custom definition for a specific type
Explanation:
Specializations tailor templates for particular arguments.
163. What does SFINAE mean?
Correct Answer: c) Substitution failure is not an error
Explanation:
Failed template substitution removes candidates instead of causing an error.
164. What does constexpr enable?
Correct Answer: d) Compile-time constant evaluation
Explanation:
constexpr functions and variables can be evaluated at compile time.
165. Can a constructor be constexpr?
Correct Answer: a) Yes, if requirements are met
Explanation:
constexpr constructors allow compile-time object initialization.
166. What is an enum class?
Correct Answer: b) A scoped enumeration
Explanation:
enum class keeps enumerators in the enum scope.
167. What does a namespace do?
Correct Answer: c) Groups identifiers
Explanation:
Namespaces organize names and avoid collisions.
168. What can using namespace std; cause?
Correct Answer: d) Name collisions
Explanation:
Importing many names can create ambiguity.
169. What is the scope resolution operator?
Correct Answer: a) ::
Explanation:
It accesses names in namespaces, classes, and global scope.
170. What does the -> operator do?
Correct Answer: b) Accesses a member through a pointer
Explanation:
Arrow combines dereference and member access.
171. What is a pointer-to-member?
Correct Answer: c) A pointer to a member of a class
Explanation:
It points to a member rather than an object address.
172. Which operator accesses a member using an object and a pointer-to-member?
Correct Answer: d) .*
Explanation:
The .* operator applies a pointer-to-member to an object.
173. Which operator accesses a member using an object pointer and a pointer-to-member?
Correct Answer: a) ->*
Explanation:
The ->* operator applies a pointer-to-member through a pointer.
174. What is type erasure?
Correct Answer: b) Hiding the concrete type behind an interface
Explanation:
Type erasure stores different types behind a common interface.
175. What concept does std::function demonstrate?
Correct Answer: c) Type erasure
Explanation:
std::function can hold many callable types with a signature.
176. What is design by contract?
Correct Answer: d) Specifying obligations for interfaces
Explanation:
Contracts define preconditions, postconditions, and invariants.
177. What is SOLID?
Correct Answer: a) A set of OOP design principles
Explanation:
SOLID guides maintainable object-oriented design.
178. What does the Single Responsibility Principle mean?
Correct Answer: b) A class should have one reason to change
Explanation:
Each class should focus on one responsibility.
179. What does the Open/Closed Principle mean?
Correct Answer: c) Open for extension, closed for modification
Explanation:
Behavior can be extended without changing existing code.
180. What does the Liskov Substitution Principle mean?
Correct Answer: d) Derived objects should be usable through base interfaces
Explanation:
Derived classes must preserve base class expectations.
181. What does the Interface Segregation Principle suggest?
Correct Answer: a) Avoid large, forced interfaces
Explanation:
Clients should not depend on unneeded methods.
182. What does the Dependency Inversion Principle suggest?
Correct Answer: b) Depend on abstractions
Explanation:
High-level modules should rely on stable interfaces.
183. What is tight coupling?
Correct Answer: c) Strong dependency between classes
Explanation:
Tightly coupled classes are hard to change independently.
184. What is loose coupling?
Correct Answer: d) Components are relatively independent
Explanation:
Loose coupling improves maintainability.
185. What is high cohesion?
Correct Answer: a) Related responsibilities are kept together
Explanation:
Cohesive classes have focused responsibilities.
186. What is low cohesion?
Correct Answer: b) Unrelated responsibilities together
Explanation:
Low cohesion makes classes harder to understand.
187. Which is an example of has-a?
Correct Answer: c) Car contains Engine
Explanation:
Containment models ownership or composition.
188. Which is an example of is-a?
Correct Answer: d) Square inherits Shape
Explanation:
Inheritance expresses a subtype relationship.
189. What does uses-a mean?
Correct Answer: a) One class uses another through methods or parameters
Explanation:
Uses relationships are often temporary dependencies.
190. What is aggregation?
Correct Answer: b) Association without necessarily owning the object
Explanation:
Aggregation is a weaker has-a relationship than composition.
191. What is composition?
Correct Answer: c) Strong has-a with lifetime ownership
Explanation:
Composed parts often live and die with the owner.
192. What is multiple dispatch?
Correct Answer: d) Function selection based on multiple objects
Explanation:
C++ natively dispatches on one dynamic type.
193. What does a pure interface class often contain?
Correct Answer: a) Only pure virtual functions
Explanation:
Interfaces often avoid state.
194. What is an abstract base class used for?
Correct Answer: b) Providing a common interface for derived classes
Explanation:
Abstract bases define shared behavior.
195. What is a covariant return type?
Correct Answer: c) An override returning a derived type
Explanation:
Overrides can return more specific pointer or reference types.
196. What does covariant return require?
Correct Answer: d) Related base and derived return types with pointers or references
Explanation:
Covariance works with related class hierarchies.
197. What is object lifetime?
Correct Answer: a) From construction to destruction
Explanation:
Lifetime is the period an object exists.
198. What is stack allocation?
Correct Answer: b) Automatic storage
Explanation:
Stack objects are created and destroyed automatically.
199. What is heap allocation?
Correct Answer: c) Dynamic allocation via new
Explanation:
Heap objects require manual or smart pointer management.
200. What is a memory leak?
Correct Answer: d) Allocated memory that is not freed
Explanation:
Leaks exhaust memory over time.
201. What is a dangling pointer?
Correct Answer: a) A pointer to freed or deleted memory
Explanation:
Dereferencing it causes undefined behavior.
202. What is double free?
Correct Answer: b) Deleting the same dynamic memory twice
Explanation:
Double free corrupts memory.
203. What is undefined behavior?
Correct Answer: c) No guaranteed result
Explanation:
The standard imposes no requirements on undefined behavior.
204. What is a vtable used for?
Correct Answer: d) Virtual function dispatch
Explanation:
The vtable enables runtime selection of overrides.
205. Which is valid virtual inheritance syntax?
Correct Answer: a) class B : virtual public A
Explanation:
virtual in the base list creates a virtual base.
206. How can ambiguous member access in multiple inheritance be resolved?
Correct Answer: b) Scope resolution or virtual inheritance
Explanation:
Qualify the base or share one base subobject.
207. What is true about object layout with a virtual base?
Correct Answer: c) It may include a virtual base pointer
Explanation:
Implementations need to locate the shared base.
208. What is a polymorphic base class?
Correct Answer: d) A class with at least one virtual function
Explanation:
Polymorphic classes support dynamic dispatch.
209. What is a final class?
Correct Answer: a) A class that cannot be inherited
Explanation:
final prevents derivation.
210. What is the C++ keyword closest to a sealed class?
Correct Answer: b) final
Explanation:
C++ uses final to prevent inheritance.
211. What is a protected destructor used for?
Correct Answer: c) Controlling deletion through derived classes or factories
Explanation:
Protected destructors restrict who can destroy objects.
212. What is a private constructor used for?
Correct Answer: d) Preventing direct object creation
Explanation:
Private constructors restrict instantiation.
213. What does the Singleton pattern often use?
Correct Answer: a) A private constructor and static accessor
Explanation:
Singleton controls creation of one instance.
214. What does the Factory pattern do?
Correct Answer: b) Creates objects without exposing exact creation logic
Explanation:
Factories encapsulate object creation.
215. What does the Observer pattern do?
Correct Answer: c) Notifies dependent objects about changes
Explanation:
Observers subscribe to subject state changes.
216. What does the Adapter pattern do?
Correct Answer: d) Converts one interface into another
Explanation:
Adapters make incompatible interfaces work together.
217. What does the Decorator pattern do?
Correct Answer: a) Adds behavior dynamically
Explanation:
Decorators wrap objects to extend functionality.
218. What does the Strategy pattern provide?
Correct Answer: b) Interchangeable algorithms
Explanation:
Strategy selects behavior at runtime.
219. What does the Command pattern do?
Correct Answer: c) Encapsulates a request as an object
Explanation:
Commands can be queued, logged, or undone.
220. What does the Template Method pattern do?
Correct Answer: d) Defines an algorithm skeleton in a base class
Explanation:
Derived classes override selected steps.
221. What does comparing two pointers usually compare?
Correct Answer: a) Addresses
Explanation:
Pointer comparison checks location, not value.
222. What operator is often overloaded to compare object contents?
Correct Answer: b) operator==
Explanation:
Equality can be defined for class types.
223. What is copy elision?
Correct Answer: c) Compiler omission of a copy operation
Explanation:
The compiler can avoid creating temporary copies.
224. What does return value optimization do?
Correct Answer: d) Reduces temporary objects
Explanation:
RVO constructs return values directly where needed.
225. What is a temporary object?
Correct Answer: a) An unnamed object created by an expression
Explanation:
Temporaries are often created during evaluation.
226. Can a const reference extend the lifetime of a temporary?
Correct Answer: b) Yes
Explanation:
A const lvalue reference can bind to a temporary.
227. What is a conversion constructor?
Correct Answer: c) A constructor that can convert from another type
Explanation:
It creates an object from a compatible argument.
228. What is a risk of conversion constructors?
Correct Answer: d) Implicit unwanted conversions
Explanation:
Implicit conversions can cause surprising behavior.
229. How can implicit constructor conversion be prevented?
Correct Answer: a) explicit
Explanation:
explicit stops implicit conversion during initialization.
230. What is a user-defined conversion operator?
Correct Answer: b) operator Type()
Explanation:
It converts an object to another type.
231. What does operator int() do?
Correct Answer: c) Converts the object to int
Explanation:
Conversion operators define type conversion.
232. What does an explicit conversion operator prevent?
Correct Answer: d) Implicit conversion in many contexts
Explanation:
explicit requires a direct cast or initialization.
233. What does = default mean for a function?
Correct Answer: a) Ask the compiler to generate the default implementation
Explanation:
Defaulted functions use compiler-generated behavior.
234. What does = delete mean for a function?
Correct Answer: b) Prevent use of the function
Explanation:
Deleted functions cause compile errors when used.
235. Why delete a copy constructor?
Correct Answer: c) To prevent copying
Explanation:
Deleted copy constructors make objects non-copyable.
236. What is a special member function?
Correct Answer: d) A constructor, destructor, copy, or move operation
Explanation:
Special members control object lifecycle operations.
237. What is aggregate initialization?
Correct Answer: a) Initializing an aggregate with braces
Explanation:
Aggregates can be initialized element by element.
238. What does POD historically stand for?
Correct Answer: b) Plain Old Data
Explanation:
POD types have simple layout and copying rules.
239. What is a trivially copyable type?
Correct Answer: c) It can be copied by copying its object representation
Explanation:
Trivially copyable types can be moved as bytes.
240. What is a standard-layout type?
Correct Answer: d) A type with C-compatible layout
Explanation:
Standard layout helps interoperability with C.
241. What is a benefit of encapsulation?
Correct Answer: a) Controlled access to data
Explanation:
Encapsulation protects internal state.
242. What is a benefit of abstraction?
Correct Answer: b) Simplifying how code is used
Explanation:
Abstraction hides complexity behind interfaces.
243. What is a benefit of inheritance?
Correct Answer: c) Code reuse and polymorphism
Explanation:
Inheritance shares behavior across related classes.
244. What is a benefit of polymorphism?
Correct Answer: d) Different implementations through a common interface
Explanation:
Polymorphism enables flexible, extensible designs.
245. What is a member function?
Correct Answer: a) A function belonging to a class
Explanation:
Member functions define class behavior.
246. What is a data member?
Correct Answer: b) A variable inside a class
Explanation:
Data members store object state.
247. What is a class invariant?
Correct Answer: c) A condition that should hold for a valid object
Explanation:
Invariants preserve object consistency.
248. What is const correctness?
Correct Answer: d) Using const to enforce immutability
Explanation:
const correctness improves safety and clarity.
249. What is true about a const object?
Correct Answer: a) Its non-mutable state cannot be modified
Explanation:
const objects cannot be changed through non-mutable members.
250. What is true about a const member function?
Correct Answer: b) It promises not to modify object state
Explanation:
const member functions support const correctness.
