Object Oriented Programming Development

1
Object Oriented ProgrammingDevelopment

• By
• Marc Conrad
• University of Luton
• Email
• Marc.Conrad_at_luton.ac.uk
• Room
• D104

2
What are we doing today?

• Introduction of
• the lecturer
• Objects
• Basic Terminology
• C
• the module

3
What is Object Oriented Programming?

• Identifying objects and assigning
  responsibilities to these objects.
• Objects communicate to other objects by sending
  messages.
• Messages are received by the methods of an object

• An object is like a black box.
• The internal details are hidden.

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What is an object?

• Tangible Things as a car, printer, ...
• Roles as employee, boss, ...
• Incidents as flight, overflow, ...
• Interactions as contract, sale, ...
• Specifications as colour, shape,

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So, what are objects?

• an object represents an individual, identifiable
  item, unit, or entity, either real or abstract,
  with a well-defined role in the problem domain.
• Or
• An "object" is anything to which a concept
  applies.
• Etc.

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Why do we care about objects?

• Modularity - large software projects can be split
  up in smaller pieces.
• Reuseability - Programs can be assembled from
  pre-written software components.
• Extensibility - New software components can be
  written or developed from existing ones.

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Example The Person class

• includeltstringgt
• includeltiostreamgt
• class Person
• char name20
• int yearOfBirth
• public
• void displayDetails()
• cout ltlt name ltlt " born in "
• ltlt yearOfBirth ltlt endl
  
• //...

private data
public processes
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The two parts of an object

• Object Data Methods
• or to say the same differently
• An object has the responsibility to know and the
  responsibility to do.

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Basic Terminology

• Abstraction is the representation of the
  essential features of an object. These are
  encapsulated into an abstract data type.
• Encapsulation is the practice of including in an
  object everything it needs hidden from other
  objects. The internal state is usually not
  accessible by other objects.

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Basic TerminologyInheritance

• Inheritance means that one class inherits the
  characteristics of another class.This is also
  called a is a relationship

A car is a vehicle
A dog is an animal
A teacher is a person
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Basic TerminologyPolymorphism

• Polymorphism means having many forms. It allows
  different objects to respond to the same message
  in different ways, the response specific to the
  type of the object.

E.g. the message displayDetails() of the Person
class should give different results when send to
a Student object (e.g. the enrolment number).
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Basic TerminologyAggregation

• Aggregation describes a has a relationship. One
  object is a part of another object.
• We distinguish between composite aggregation (the
  composite owns the part) and shared aggregation
  (the part is shared by more then one composite).

A car has wheels.
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Basic TerminologyBehaviour and Messages

• The most important aspect of an object is its
  behaviour (the things it can do). A behaviour is
  initiated by sending a message to the object
  (usually by calling a method).

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The two steps of Object Oriented Programming

• Making Classes Creating, extending or reusing
  abstract data types.
• Making Objects interact Creating objects from
  abstract data types and defining their
  relationships.

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Historical Notes

• C owes most to C. Other ancestors are
  Simula67and Algol68.
• First versions of C in 1980 under the name C
  with classes. Since 1983 the name C is used.
• 1990 ANSI/ISO 9899 defines a standard for C
• 1998 ISO/IEC 14882 specifies the standard for C

C 1987
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C and C

• C is a subset of C.Advantages Existing C
  libraries can be used, efficient code can be
  generated.But C has the same caveats and
  problems as C (e.g. pointer arithmetic,).
• C can be used both as a low level and as a high
  level language.

We focus on the high level aspects.
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C and Java

• Java is a full object oriented language, all code
  has to go into classes.
• C - in contrast - is a hybrid language, capable
  both of functional and object oriented
  programming.

So, C is more powerful but also more difficult
to handle than Java.
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Module Outline

• Introduction
• The non object oriented basics
• Classes
• Design Approaches
• Testing

• Inheritance
• Aggregation
• Polymorphism
• Multifile Development

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Assessment Details

• 50 in course and 50 exam.
• For more details for the in course assignment see
  separate handout.

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Books

• Teach Yourself C in 10 minutes,J. Liberty,
  SAMS 1999.
• C - How to program, Deitel Deitel, Prentice
  Hall, 2001.
• Object Oriented Programming with C, David
  Parson, Letts Educational, London 1997.

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Websites

• A C online tutorialhttp//www.cplusplus.com/do
  c/tutorial/
• The C FAQhttp//www.parashift.com/c-faq-lite
  
• The homepage of Bjarne Stroustrup, the inventor
  of Chttp//www.research.att.com/bs

And many, many more!