Interview Questions on Constructor in C++ Programming

The best way to prepare for an interview is reviewing the list of common questions asked in interviews like the one below.

1. What are constructor in C++ Programming?

A constructor in C++ is the function that is executed when an instance of a class is created. A constructor is called automatically when the object of the class with the constructor is created. The function can have parameters which are passed to it.

Constructors are invoked automatically when an instance of a class is created, so they are used to initialize variables with values set by default or values set by user input. This initialization method is called Default Constructor because it's the one we get for free and we don't need to define it.

2. What does a C++ constructor do?

A constructor is a special type of function which is used to initialize an object. This function will be called automatically when an object is created. The constructor also ensures that the values passed to the object are not null or invalid.

A C++ constructor achieves this by using a default value for the parameter, ensuring that any values passed to the parameters are not null or invalid, and initializing each variable in the class with a value from its parameter list.

3. What are the benefits of using constructor in C++?

There are various benefits of using constructor in C++.

These include:

  • It helps identify the type of an object at compile time.
  • Constructors allow us to initialize values in the object before its use by other functions or code.

4. How to use the constructor in C++?

A constructor is a special kind of function. It creates an object in memory, and its job is to initialize that object before it’s used. And here are some things that you need to know about constructors:

  1. Constructors are functions, but they have the name of the class.
  2. The arguments passed to a constructor are called arguments of initializers.
  3. The arguments passed to a constructor must be constants or previously declared members of the same class or inherited members from parent classes (in other words, they can't change).
  4. Constructors cannot return values which means they cannot use the return statement. Instead, they yield an object using the "this" keyword.

5. How many types of constructors are there in C++?

There are many different types of constructors in C++.

The main types of constructors in C++ are:

  1. Default: Default constructor is the one that will be called when you declare a new object without supplying any parameters.
  2. Copy: C++ Copy constructor is the one that will be called when a copy of a class object is created. It can be used to initialize the new object's values from those of the old one.
  3. Move: The C++ move constructor is called when a class is assigned to another variable. This should be the default constructor for any class, and it can be used to make a copy of an object.
  4. Virtual: The virtual constructor has a default implementation that will be called when an object of a given type is constructed. This defaults to calling the copy constructor on the object, which will initialize the object by copying it from another object of the same type.

To prepare for the C++ interview, why not try our MCQ on constructors in C++ and other C++ interview questions? All the best for your technical interview!

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