CS Week 8 - Inheritance and Polymorphism

Question 1

Derived class

Answer 1

a class that is derived from another class (base class or superclass)

Question 2

Inheritance

Answer 2

the derived class inherits the properties of the base class

Question 3

Declaring a derived class

Answer 3

place “:” after derived class name, followed by a member access specifier like “public” and base class name

class DerivedClass:public BaseClass {…};

Question 4

member access

Answer 4

Members of a derived class have access to the public members of the base class, but not to the private members of the base class

Question 5

protected
private
public

Answer 5

protected - accessible by self and derived classes
private - only accessible by self
public - accessible by anyone

Question 6

specifiers in the class definition

Answer 6

public - “public->public, protected->protected” - public members of base are accessible as public members of Derived and protected members of base are accessible as protected members of derived

protected - “public->protected, protected->protected” - public and protected members of base are accessible as protected members of derived

private - “public->private, protected->private” - public and protected member of base are accessible as private members of derived, this is the default if none of these are typed (class derived :base{..};)

Question 7

override

Answer 7

When a derived class defines a member function with same name and parameters as a base class function, member function overrides the base class function

Question 8

override vs overloading

Answer 8

Overloading has different parameters, derived function does not hide base function
Overriding, all the same

Question 9

hasa vs isa

Answer 9

Has-a - object has an object, no inheritance

Is-a - object is a kind of object

Question 10

Polymorphism

Answer 10

determining which program behavior to execute depending on data types

Question 11

Compile-time polymorphism

Answer 11

when the compiler determines which function to call at compile time

Question 12

Runtime polymorphism

Answer 12

when the compiler is unable to determine which function to call at compile time, so the determination is made while the program is running

Question 13

derived/base class pointer conversion

Answer 13

where a pointer to a derived class is converted to a pointer to the base class without explicit casting

Question 14

Virtual function

Answer 14

member function that may be overridden in a derived class and is used for runtime polymorphism

Declared by prepending the keyword “virtual”, ex virtual string GetDescription() const

At runtime, when a virtual function is called using a pointer, the correct function to call is dynamically determined based on the actual object type to which the pointer or reference refers

Question 15

override

Answer 15

keyword -optional - indicate that a virtual function is overridden in a derived class

Question 16

virtual table

Answer 16

To implement virtual functions, the compiler creates a virtual table that allows the computer to quickly lookup which function to call at runtime

Table contains an entry for each virtual function with a function pointer that points to the most-derived function that is accessible to each class

Looking up which function to call makes runtime polymorphism slower than compile-time polymorphism

Question 17

Pure virtual function

Answer 17

a virtual function that provides no definition in base class and all derived classes must override it

Declared like a virtual function but assigned with 0

virtual string GetHours() const = 0;

Question 18

Abstract base class

Answer 18

class that has at least one pure virtual function
Cannot declare as an object

Question 19

Classes

Answer 19

a class encapsulates data and behavior to create objects

Question 20

Inheritance

Answer 20

allows one class (subclass) to be based on another class (a base class or superclass)

Question 21

Abstract classes

Answer 21

a class that guides the design of subclasses but cannot itself be instantiated as an object

Question 22

Pure virtual function

Answer 22

not implemented in base class, all derived classes must override the function

virtual type name() = 0;

Question 23

Abstract class

Answer 23

cannot be instantiated as an object

Is the superclass for a sub class and specifies how subclasses must be implemented

When class has one or more pure virtual functions

Question 24

Concrete class

Answer 24

not abstract, can be instantiated

Question 25

Unified modeling language (UML)

Answer 25

a language for software design that uses different types of diagrams to visualize the structure and behavior of program

Question 26

Structural diagram

Answer 26

visualizes static elements of software, such as attributes (variables) and operations (functions) used in the program

Question 27

Behavioral diagram

Answer 27

visualizes dynamic behavior of software, such as the flow of an algorithm

Question 27

A UML class diagram

Answer 27

a structural diagram that can be used to visually model the classes of a computer program, including member variables and functions

Question 27

Project management tools

Answer 27

automate the compilation and linking process

Question 28

Make

Answer 28

one project management tool that is commonly used on Unix and Linux computer systems

Question 29

makefile

Answer 29

to recompile and link a program whenever changes are made to the source or header files

Question 30

Makerules

Answer 30

used to specify dependencies between a target file (object files and executable) and a set of prerequisite files that are needed to generate the target file (source and header files)

Question 31

make recipe

Answer 31

A make rule can include one or more commands - referred to as make recipe that will be executed in order to generate the target file

Question 32

Enumeration type

Answer 32

enum - declared a name for a new type and possible values for that type