What is the purpose of the 'const' keyword when used with member functions?

The correct answer is B: To prevent modification of member variables within the function. A const member function cannot modify any member variables of the object. It guarantees that the function will not alter the state of the object.

In C++, when a derived class object is created, which constructor is called first?

The correct answer is B: Base class constructor. The base class constructor is always called before the derived class constructor to ensure proper initialization of inherited members.

Which type of inheritance can lead to the Diamond Problem in C++?

The correct answer is B: Multiple inheritance. Multiple inheritance can lead to the Diamond Problem where a class inherits from two classes that share a common base. This is solved using virtual inheritance.

What is the output of operator overloading in the following context? class Complex { public: int real, imag; Complex operator+(const Complex &c) { Complex temp; temp.real = real + c.real; temp.imag = imag + c.imag; return temp; } }; Complex c1, c2, c

The correct answer is A: c3 has real=4, imag=6. The + operator is overloaded to add two Complex numbers. c1 + c2 calls the overloaded operator+, resulting in real=1+3=4 and imag=2+4=6.

What happens when you try to access a private member of a class from outside?

The correct answer is B: Compilation error. Accessing private members from outside the class results in a compilation error. The compiler enforces access control at compile time.

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C++ Programming

Object oriented C++ for GATE and placement

49 Q 1 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 49

Topics in C++ Programming

All OOP Concepts 100

Q.1 Medium OOP Concepts

In C++, when a derived class overrides a virtual function from a base class, which access specifier must be used to ensure proper polymorphic behavior?

A The derived class function must use the same access specifier as the base class

B The derived class function can use any access specifier regardless of base class

C The derived class function must always be public

D The derived class function must be private for security

Correct Answer: B. The derived class function can use any access specifier regardless of base class

EXPLANATION

In C++, a derived class can override a virtual function with a different access specifier than the base class. The access specifier controls who can call the function, but it doesn't affect the polymorphic behavior. However, it's a best practice to maintain the same access level.

Test

Q.2 Medium OOP Concepts

Which of the following best describes the concept of method overloading?

A Multiple functions with the same name and same parameters

B Multiple functions with the same name but different parameters or return types

C A derived class defining a function with the same name as the base class

D Using virtual functions to achieve runtime polymorphism

Correct Answer: B. Multiple functions with the same name but different parameters or return types

EXPLANATION

Method overloading allows multiple functions with the same name but different parameter lists (number, type, or order). Return type alone is insufficient for overloading.

Test

Q.3 Medium OOP Concepts

What is the primary use of the 'const' keyword when applied to member functions?

A To prevent the function from modifying object data members

B To prevent the function from being called

C To make the function static

D To optimize function execution speed

Correct Answer: A. To prevent the function from modifying object data members

EXPLANATION

A const member function cannot modify any non-static data members of the object. It guarantees that calling the function will not change the object's state.

Test

Q.4 Medium OOP Concepts

Which of the following statements about constructors is correct?

A Constructors can have a return type

B Constructors are automatically called when an object is created

C A class can have only one constructor

D Constructors are inherited automatically in all derived classes

Correct Answer: B. Constructors are automatically called when an object is created

EXPLANATION

Constructors have no return type, a class can have multiple constructors (constructor overloading), and constructors are not automatically inherited in C++ (until C++11 explicit inheritance). They are automatically invoked when objects are created.

Test

Q.5 Medium OOP Concepts

What is the output of the following code?
class A { public: virtual void func() { cout

A A

B B

C C

D Compilation Error

Correct Answer: C. C

EXPLANATION

With virtual functions, the actual object type (C) determines which function is called, not the pointer type. C::func() is invoked through multilevel inheritance.

Test

Q.6 Medium OOP Concepts

Consider a scenario where a derived class needs to access a base class member that should not be accessible to external code. Which access specifier should be used in the base class?

A public

B protected

C private

D internal

Correct Answer: B. protected

EXPLANATION

The 'protected' access specifier allows access within the class and derived classes, but not to external code. This is ideal for members that derived classes need to use but external code should not access.

Test

Q.7 Medium OOP Concepts

What will be the output of the following code?
class Base { public: void show() { cout

A Base

B Derived

C Compilation Error

D Runtime Error

Correct Answer: A. Base

EXPLANATION

Without virtual keyword, function overriding doesn't occur. The pointer type (Base*) determines which function is called, so Base::show() is invoked.

Test

Q.8 Medium OOP Concepts

In which scenario would you use an abstract base class instead of a concrete base class?

A When you want to create many instances of the base class

B When you want to define an interface that derived classes must implement

C When you want faster execution

D When you want to save memory

Correct Answer: B. When you want to define an interface that derived classes must implement

EXPLANATION

Abstract base classes are used to define interfaces and contracts that derived classes must follow. They cannot be instantiated but force derived classes to implement certain behaviors through pure virtual functions.

Test

Q.9 Medium OOP Concepts

Which of the following is an example of operator overloading as a member function?

A friend ostream& operator

B Class operator+(const Class&);

C operator Class() { return *this; }

D operator==() friend function

Correct Answer: B. Class operator+(const Class&);

EXPLANATION

Option B shows operator overloading as a member function. The operator is defined as a member function of the class, which takes the second operand as a parameter.

Test

Q.10 Medium OOP Concepts

What is the primary advantage of using virtual functions in a base class?

A To improve compilation speed

B To enable runtime polymorphism and allow derived classes to override behavior

C To reduce memory usage

D To make functions faster

Correct Answer: B. To enable runtime polymorphism and allow derived classes to override behavior

EXPLANATION

Virtual functions enable runtime polymorphism, allowing the correct derived class method to be called through a base class pointer or reference, facilitating flexible and extensible code design.

Test

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