Lecture 21

Question 1

Polymorphism is

Answer 1

one of the central ideas of object-orientation (OO): that a single object may take on multiple different roles within a program.

Question 2

The word originates from Greek,

meaning

Answer 2

– “poly”: many

– “morph”: forms

Question 3

class Shape
{
public:
virtual double area() = 0;
virtual double perimeter() = 0;
}
//=0 does what?

Answer 3

The “= 0” on each method indicates that our class Shape
does not define the method – it is the responsibility of
any class fulfilling this role to implement them instead.

Question 4

class Shape
{
public:
virtual double area() = 0;
virtual double perimeter() = 0;
}
//virtual means what?

Answer 4

The keyword “virtual” on the methods indicates that
Shape expects implementing classes to provide their own
definition, and will allow those to be accessed from the
Shape perspective.

Question 5

class Circle: public Shape
{
public:
Circle(double r);
double area();
double perimeter();
void draw();
private:
double radius;
}
//public shape allows what?

Answer 5

public shape-indicates that
Circle is inheriting the specifications and
preexisting blueprint of the type Shape.
public indicates that the original access
modifiers of Shape should remain
unchanged.