Object Oriented Programming
Development
By:
Marc Conrad
University of Luton
Email:
Marc.Conrad@luton.ac.uk
Room:
D104
1
What are we doing today?
Introduction of:
the lecturer
Objects
Basic Terminology
C++
the module
2
What is Object Oriented
Programming?
An object is like a
black box.
The internal
details are
hidden.
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
3
What is an object?
Tangible Things
Roles
Incidents
Interactions
Specifications
as a car, printer, ...
as employee, boss, ...
as flight, overflow, ...
as contract, sale, ...
as colour, shape, …
4
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.
5
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
#include<string>
#include<iostream>
class Person{
private
char name[20];
data
int yearOfBirth;
public:
void displayDetails() {
cout << name << " born in "
<< yearOfBirth << endl;
public
}
processes
//...
};
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.
=
+
8
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.
9
Basic Terminology:
Inheritance
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
10
Basic Terminology:
Polymorphism
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 Terminology:
Aggregation
Aggregation describes a “has a”
relationship. One object is a part of
another object.
A car has wheels.
We distinguish between composite
aggregation (the composite “owns” the
part) and shared aggregation (the part is
shared by more then one composite).
12
Basic Terminology:
Behaviour 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).
13
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.
14
Historical Notes
C++ owes most to C.
Other ancestors are Simula67
C++ 1987
and 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
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standard for C++
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.
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high
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.
17
Module Outline
Introduction
The non object
oriented basics
Classes
Design Approaches
Testing
Inheritance
Aggregation
Polymorphism
Multifile Development
18
Assessment Details
50% in course and 50% exam.
For more details for the in course
assignment see separate handout.
19
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.
20
Websites
A C++ online tutorial:
http://www.cplusplus.com/doc/tutorial/
The C++ FAQ:
http://www.parashift.com/c++-faq-lite
The homepage of Bjarne Stroustrup, the
inventor of C++:
http://www.research.att.com/~bs
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