Free Test Virtual base classes a... – C++ Lan...

Q1: What is the main purpose of a virtual base class?

A. To avoid multiple copies of a base class in multiple inheritance B. To make a class abstract C. To allow runtime polymorphism D. To restrict access to base class members

Q2: Which keyword is used to declare a virtual base class?

A. virtual B. base C. inherit D. abstract

Q3: What problem does virtual inheritance solve?

A. Diamond problem B. Slicing problem C. Memory leak D. Access violation

Q4: How do virtual functions enable runtime polymorphism?

A. By allowing function overriding and dynamic dispatch B. By compile-time binding C. By static function calls D. By function overloading

Q5: Which table is used by C++ to support virtual function calls?

A. Virtual table (vtable) B. Function pointer table C. Jump table D. Call stack

Q6: When a virtual function is called through a base class pointer, which function is executed?

A. Derived class version if overridden B. Base class version only C. Compiler error D. Depends on function visibility

Q7: Can constructors be declared virtual?

A. No, constructors cannot be virtual B. Yes, always C. Only in abstract classes D. Only base constructors

Q8: What happens if a base class has a virtual destructor?

A. Derived class destructors are called properly B. Derived class destructors are ignored C. Only base destructor is called D. Compiler error

Q9: If a class contains a virtual function, what does it typically contain?

A. Pointer to vtable B. Function pointer table C. Static function table D. No additional members

Q10: Can a virtual function be called from a constructor?

A. Yes, but calls base class version B. Yes, calls derived version C. No, not allowed D. Only if explicitly called

Q11: What is the diamond problem in multiple inheritance?

A. Multiple inheritance paths to the same base class B. Ambiguous function overloading C. Constructor ambiguity D. Multiple virtual functions

Q12: How does virtual inheritance address the diamond problem?

A. By sharing one common base class instance B. By disabling multiple inheritance C. By duplicating base class members D. By hiding base class

Q13: Which of the following is true about virtual base classes?

A. They are initialized by the most derived class B. They are initialized by intermediate classes C. They cannot have constructors D. They are static classes

Q14: What keyword is used to override a virtual function explicitly in derived class?

A. override B. virtual C. final D. abstract

Q15: Can a virtual function be pure virtual?

A. Yes, to make class abstract B. No, virtual functions cannot be pure C. Only in base classes D. Only in derived classes

Q16: What happens if a pure virtual function has a body?

A. It is allowed and can be called B. Compilation error C. Runtime error D. Undefined behavior

Q17: Which keyword prevents further overriding of a virtual function?

A. final B. override C. const D. virtual

Q18: How do you declare a virtual destructor?

A. virtual ~ClassName() {} B. ~ClassName() virtual {} C. destructor virtual ClassName() D. virtual destructor ClassName()

Q19: Which of the following is NOT true about virtual functions?

A. They support dynamic dispatch B. They cannot be static C. They are resolved at compile time D. They enable runtime polymorphism

Q20: What is vptr?

A. A pointer in each object pointing to its vtable B. A virtual function C. A base class pointer D. A friend function

Quiz for Virtual base classes and virtual functions