Function Overloading in C++
15 questions · 12 min · Medium
Friend Functions in C++
Test your knowledge of friend functions in C++, including friend declarations, private and protected member access, syntax, classes, and common use cases.
- 15
- Questions
- 12 min
- Time limit
- Medium
- Difficulty
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All 15 questions and answers Spoilers: this shows the questions and answers. Try the quiz first! Open
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1. What is a friend function in C++?
- A. A function that can access private and protected members of a class
- B. A function that can only access public members
- C. A function that must be a class member
- D. A function that cannot access class data
Show answer
A. A function that can access private and protected members of a class
A friend function is not a member of the class, but it is granted access to the class's private and protected members.
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2. Which keyword is used to declare a friend function in C++?
- A. friend
- B. private
- C. access
- D. trusted
Show answer
A. friend
The friend keyword is used inside a class declaration to grant a function or another class access to private and protected members.
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3. Where is a friend function typically declared?
- A. Inside the class declaration
- B. Only inside main()
- C. Only inside a namespace
- D. Inside a header file only
Show answer
A. Inside the class declaration
A friend function is declared inside the class using the friend keyword, although its definition is normally outside the class.
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4. Is a friend function a member function of the class that declares it?
- A. No
- B. Yes, always
- C. Only if it is private
- D. Only if it is static
Show answer
A. No
A friend function is a non-member function that has been granted special access to the class.
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5. Which access levels can a friend function access directly?
- A. Private and protected
- B. Public only
- C. Protected only
- D. Private only
Show answer
A. Private and protected
Friend functions can directly access private and protected members of the class that grants friendship.
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6. Which of the following is a correct friend function declaration?
- A. friend void display();
- B. friendly void display();
- C. friendship void display();
- D. private void display();
Show answer
A. friend void display();
The friend keyword followed by the function declaration correctly declares a friend function inside a class.
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7. How is a friend function normally called?
- A. Like a regular non-member function
- B. Only using the dot operator
- C. Only using the arrow operator
- D. Only through the class constructor
Show answer
A. Like a regular non-member function
Because a friend function is not a member function, it is normally called like an ordinary function rather than through an object using the dot operator.
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8. Can a friend function be declared in more than one class?
- A. Yes, the same function can be declared as a friend of multiple classes
- B. No, it can only belong to one class
- C. Only if all classes are derived classes
- D. Only if the function is static
Show answer
A. Yes, the same function can be declared as a friend of multiple classes
A non-member function can be declared as a friend by multiple classes, allowing it to access the private and protected members of each class.
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9. Which statement about friendship in C++ is correct?
- A. Friendship is not automatically inherited
- B. Friendship is always inherited
- C. Friendship is automatically transferred to every derived class
- D. Friendship applies to all classes in the program
Show answer
A. Friendship is not automatically inherited
Friendship is granted explicitly and is not automatically inherited by derived classes.
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10. Is friendship in C++ automatically mutual?
- A. No
- B. Yes, always
- C. Only between derived classes
- D. Only for constructors
Show answer
A. No
If class A declares class B as a friend, that does not automatically make A a friend of B.
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11. Can a friend function be declared as a member of another class?
- A. Yes, a member function of another class can be declared as a friend
- B. No, friend functions must always be global functions
- C. Only if both classes have the same name
- D. Only if both classes are abstract
Show answer
A. Yes, a member function of another class can be declared as a friend
C++ allows a specific member function of another class to be declared as a friend.
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12. What is one common use of friend functions?
- A. Allowing closely related external functions to access private data
- B. Preventing all access to class members
- C. Replacing every constructor
- D. Creating namespaces automatically
Show answer
A. Allowing closely related external functions to access private data
Friend functions are useful when an external function needs controlled access to a class's private or protected data.
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13. Which operator is commonly overloaded using a friend function because the left operand may not be an object of the class?
- A. operator<<
- B. operator.
- C. operator::
- D. operator?
Show answer
A. operator<<
The stream insertion operator is commonly implemented as a friend function so it can access private data while supporting expressions such as std::cout << object.
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14. Which statement about a friend function is correct?
- A. It does not have a this pointer
- B. It always has a this pointer
- C. It must be declared static
- D. It must be declared private
Show answer
A. It does not have a this pointer
A friend function is not a member function, so it does not have the implicit this pointer.
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15. Which statement best describes the purpose of the friend keyword in C++?
- A. It grants specific non-member functions or classes access to private and protected members
- B. It makes every member public
- C. It creates an inheritance relationship
- D. It prevents a class from being instantiated
Show answer
A. It grants specific non-member functions or classes access to private and protected members
The friend keyword provides selective access to private and protected members without making the function or class a member of the granting class.