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Computer Science > Section 12 - Object-Orientated Programming - USE NOTES > Flashcards

Section 12 - Object-Orientated Programming - USE NOTES Flashcards

1
Q

What is a procedural language?

A

A program consisting of:
- Step-by-step instructions
- Function and procedure calls
- Local and global variables

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2
Q

How does procedural programming work?

A

Code is broken down into a number of smaller modules, with the program consisting of a series of calls to procedures and functions, each of which may in turn call other procedures or functions

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3
Q

How does object orientated programming work?

A

The world is viewed as a system of objects, each of which is responsible for its own data and the operations on that data. All processing carried out is done by the objects

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4
Q

What are attributes?

A

Data that is associated with the class

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5
Q

What features do objects have?

A
  • Attributes
  • State
  • Behaviours
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6
Q

What are states?

A

The value of an objects instance variables

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7
Q

What are behaviours?

A

Actions that can be performed by an object

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8
Q

What is a class?

A

A blueprint or template for an object that defines the attributes and behaviours of those objects

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9
Q

What is a method?

A

Attributes and behaviours of an object, they are the functionality of a class

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10
Q

What is a constructor?

A

Something used to create objects in a class

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11
Q

What are setter methods?

A

Procedures

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12
Q

What are getter methods?

A

Functions

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13
Q

What is instantiation?

A

Where a new object (an instance of a class) is created

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14
Q

Can multiple instances of the same class be created?

A

Yes, they will share identical methods and attributes, however the value of their attributes will be unique to each instance

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15
Q

What is a reference type variable?

A

Variables that hold a pointer or reference to where the object itself is stored

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16
Q

What is a variable reference diagram?

A

A graphical form showing how objects are referenced by reference variables

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17
Q

What is an instance of a class?

A

Objects created from that class

18
Q

What is encapusaltion?

A

All the data and methods of an object are combined into a single entity so that the attributes or behaviours of one object cannot affect the way in which another object functions

19
Q

What is a subclass?

A

A “child” class in object-orientated programming

19
Q

Why do programmers use encapsulation?

A
  • Different programmers can work on different classes and not have to worry about how other parts of the system may affect any code they write
  • They can use methods from other classes without having to know how they work
20
Q

How can you determine whether to use inheritance?

A

Use the “is a” rule. Ask “is object A an object B?”, and if it is then object A should inherit the data and behaviours from object B

21
Q

What is a superclass?

A

A “parent” class in object-orientated programming

21
Q

What is an inheritance diagram?

A

A diagram showing the inheritance relationship between different classes

21
Q

What is inheritance?

A

Child classes inherit data and behaviours from their parent class

22
Q

What is association?

A

A “has a” relationship between classes, meaning there is no ownership between objects and they can be created and deleted independently

23
Q

What is aggregation?

A

A more specific interpretation where a class is a collection or container of other classes, however they do not have a lifecycle dependency

24
Q

What is composition?

A

A stronger form of association, where if the container object is destroyed then every instance of the contained class is also destroyed

25
Q

How is aggregation shown in class diagrams?

A

A hollow diamond shape next to the container object

26
Q

How is composition shown in class diagrams?

A

A filled in diamond shape next to the container object

27
Q

What is polymorphism?

A

A programming languages ability to process objects differently depending on their class.

28
Q

What is overriding?

A

Defining a method with the same name and formal argument types as a method inherited from a superclass

29
Q

Why is composition favoured over inheritence?

A
  • It allows for greater flexibility as composition is a less rigid relationship between the 2 objects
  • An object may be composed of several other objects but cannot be said in a real-world sense to “inherit” their characteristics
30
Q

What is information hiding?

A

Where the objects instance variables are hidden so other objects must use messages to interact with that object’s state

31
Q

What are the 3 access modifiers?

A
  • Public
  • Private
  • Protected
32
Q

What can access a method/instance variable that has been declared public?

A

Code within any class

33
Q

What can access a method/instance variable that has been declared private?

A

Code within the class itself can access it

34
Q

What can access a method/instance variable that has been declared protected?

A

The definition varies between languages, however the most common definitions are only members of the same subclass, and only members in the same package/library of classes

35
Q

What is an interface?

A

A collection of abstract methods that a group of unrelated classes may implement

36
Q

What is the advantage of using an interface?

A

New classes can be added which use the interface without affecting existing classes

37
Q

What is the point of encapsulating what varies?

A

It reduces maintenance and testing effort

38
Q

What is encapsulating what varies?

A

When something changes in a program, if the concept in question is encapsulated in a single module then only that module needs to change

39
Q

What are the advantages of OOP?

A
  • The object-orientated methodology forces programmers to go through extensive planning, making better designs with less weaknesses
  • Encapsulation means that source code for an object can be written, tested and maintained independently of the code for other objects
  • Once an object is created, knowledge of how its methods are implemented is no necessary for it to be used
  • New objects with small differences to existing ones can be created easily
  • Objects that are already defined, coded and tested can be reused in other programs
  • An object-orientated program is much easier to maintain because of its modular structure

Computer Science (13 decks)

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