Creating objects in C++ - Quick Revision & Summary

Recall & Review

beginner

What is an object in C++?

An object is a specific instance of a class that holds data and can perform actions defined by the class.

beginner

How do you create an object of a class named <code>Car</code>?

You create an object by declaring it with the class name, like: <code>Car myCar;</code>

intermediate

What is the difference between creating an object on the stack vs the heap in C++?

Stack objects are created with simple declarations and automatically destroyed when out of scope. Heap objects are created with new and must be manually deleted.

beginner

What does the new keyword do when creating an object?

new allocates memory on the heap and returns a pointer to the newly created object.

beginner

How do you delete an object created with new?

You use the delete keyword followed by the pointer to free the memory, like: delete myObject;

How do you create an object named dog of class Animal on the stack?

A new Animal dog;

B Animal* dog = new Animal();

C Animal dog;

D Animal dog = new Animal();

Declaring Animal dog; creates an object on the stack.

Which keyword is used to create an object on the heap?

A new

B alloc

C create

D malloc

The new keyword allocates memory on the heap for an object.

What must you do after creating an object with new to avoid memory leaks?

A Use <code>free()</code> function

B Call the destructor manually

C Nothing, it cleans up automatically

D Use <code>delete</code> to free memory

You must use delete to free memory allocated by new.

What type of variable holds the address of an object created with new?

A Pointer

B Reference

C Integer

D Array

Objects created with new return a pointer to the object.

Which of the following creates an object on the heap?

A Car myCar;

B Car* myCar = new Car();

C Car myCar = Car();

D Car myCar = &Car();

Car* myCar = new Car(); creates an object on the heap and stores its address in a pointer.

Explain how to create an object of a class in C++ both on the stack and on the heap.

Think about simple declaration vs using new keyword.

Describe why it is important to use delete with objects created using new.

Consider what happens if memory is not freed.