Introduction to C++ I

Question 1

What is C++?

Answer 1

Object-oriented language built on top of C.

Question 2

What are some functionalities of C++?

Answer 2

• Operator overloading
• We have classes and objects
• Namespaces for organisation
• Pass-by-reference
• In C++ usage of objects implicitly triggers default or programmer defined functions for managing lifecycle.

Question 3

What are the types/visibility of member variables we can have in a C++ class?

Answer 3

• private
• public
• protected
• friend
• static

Question 4

Where are constructors of classes typically declared?

Answer 4

In the public scope (can be protected or private).

Question 5

What does public declaration of a class allow?

Answer 5

• Initialisation
• Copying (duplication of resource)
• Moving (transferring ownership of resource)

Question 5

What does a destructor deceleration specify?

Answer 5

Destructor declaration specifies how to clean up a class type.

Question 6

When are destructors callled?

Answer 6

Destructors are automatically called when a class is deleted (e.g. out of scope or explicitly free the memory allocated for the class).

Question 6

What are member functions?

Answer 6

Functions of the class that do stuff. Specify name, parameters, return type.

Question 7

What are const functions?

Answer 7

Functions that do not change the state of the class.

Question 8

Can member function be declared and defined in the header class?

Answer 8

Yes, we can provide implementation as well in the header file.

Question 9

What is the default visibility for a class member?

Answer 9

Private

Question 10

What visibility can C++ class members be?

Answer 10

• private
• public
• protected

Question 11

Where are private members accessible from?

Answer 11

Inside the class or through member functions.

Question 12

Where are public members accessible?

Answer 12

Outside the class (they form the class interface) and should either be accessors or mutators.

Question 13

Do we use header guards in C++?

Answer 13

Yes, they are needed in the header files.

Question 14

What is the encourage method of storing declaration and implementation?

Answer 14

Store the declaration in the header and the definition/implementation in an implementation file (.cpp).

Question 15

What are initialisation lists?

Answer 15

Used to set a member variable to function parameter value.

Question 16

What is the this pointer?

Answer 16

A pointer to the current instance of the class object, only visible withing a member function of a class instance. Only needed if you have to refer to class member.

Question 17

What is stored in the dereferencing of *this?

Answer 17

*this is the value at the address of the class instance.

Question 18

What is overloading?

Answer 18

Multiple functions with the same name, but different parameters and qualifiers (e.g. const)

Question 19

What are structs in C++?

Answer 19

They are classes where visibility is default public.

Question 20

How are structs in C++ different to C?

Answer 20

Structs in C++ have the option to add functions to them but you don’t have to.

Question 21

What happens when a class instance is out of scope?

Answer 21

The destructor is automatically called.

Question 22

If we use the new keyword what must we use later in the program?

Answer 22

delete, when we have finished using a variable.

Question 23

If we use the new[] keyword what must we use later in the program?

Answer 23

delete[]

Question 24

What is are the comparison of C and C++ dynamic allocation?

Answer 24

• C allocates raw bytes of memory with malloc.
• C++ allocates memory for a number of elements
• C scaling is easy to forget (sizeof(int)!)
• In C++ byte scaling is implicit

Question 25

Why do we need namespaces?

Answer 25

• Large codebases can have many hundreds of types and functions.
• Everyone wants to name their types and functions concisely and succinctly (in a brief manner)
• Allows us to deal with many similar but unrelated things sharing a common namespace.

Question 26

How do we avoid using a namespace repeatedly in a file?

Answer 26

‘using’ keyword

Question 27

How do we represent true or false in C++?

Answer 27

Using bool (which is not available in C).

Question 28

What can we do with bool and int in C++?

Answer 28

Convert implicitly to each other.

Question 29

What is wchar_t?

Answer 29

Wide character. ASCII is limited to the values 0-127 (7 bits). Not enough for some languages.

Question 30

What is nullptr in C++?

Answer 30

Keyword used instead of NULL in C++.

Question 31

What are namespaces?

Answer 31

Namespaces are a way to logically group and organize code elements such as classes, functions, and variables to prevent naming conflicts and improve code readability and maintainability.

Question 32

What is encapsulation?

Answer 32

The process of bundling information into objects such as classes. Helps hide the internal state of an object and prevents unintended modifications.

Question 33

What is a const variable?

Answer 33

A variable that cannot be changed once it has been initialized.

Question 34

What is undefined behaviour?

Answer 34

Situations where the behavior of a program is not defined by the language specification and instead relies on the compiler, leading to unpredictable outcomes that can include crashes, unexpected results, or seemingly correct behavior.