CS2203 OBJECT ORIENTED PROGRAMMING 3 0 0 3

1
CS2203 OBJECT ORIENTED PROGRAMMING
3 0 0 3

• 
  (Common to CSE IT)
• Aim
• To understand the concepts of object-oriented
  programming and master OOP using C.
• Unit I
  
  
  
  9
• Object oriented programming concepts objects
  classes methods and messages abstraction and
  encapsulation inheritance abstract classes
  polymorphism. Introduction to C classes
  access specifiers function and data members
  default arguments function overloading friend
  functions const and volatile functions static
  members Objects pointers and objects
  constant objects nested classes local classes
• Unit II
  
  
  
  9
• Constructors default constructor
  Parameterized constructors Constructor with
  dynamic allocation copy constructor
  destructors operator overloading overloading
  through friend functions overloading the
  assignment operator type conversion explicit
  constructor
• Unit III
  
  
  
  9
• Function and class templates - Exception handling
  try-catch-throw paradigm exception
  specification terminate and Unexpected
  functions Uncaught exception.
• Unit IV
  
  
  
  9
• Inheritance public, private, and protected
  derivations multiple inheritance virtual base
  class abstract class composite objects
  Runtime polymorphism virtual functions pure
  virtual functions RTTI typeid dynamic
  casting RTTI and templates cross casting
  down casting .
• Unit V
  
  
  
  9
• Streams and formatted I/O I/O manipulators -
  file handling random access object
  serialization namespaces - std namespace ANSI
  String Objects standard template library.
• 
  
  
  Total 45
• TEXT BOOKS
• 1. B. Trivedi, Programming with ANSI C,
  Oxford University Press, 2007.
• REFERENCES
• 1. Ira Pohl, Object Oriented Programming using
  C, Pearson Education, Second

2
Unit I

• Object oriented programming concepts objects
  classes methods and messages abstraction and
  encapsulation inheritance abstract classes
  polymorphism.
• Introduction to C classes access specifiers
  function and data members default arguments
  function overloading friend functions const
  and volatile functions static members Objects
  pointers and objects constant objects
  nested classes local classes

3
Objects

• An object is an encapsulation of both functions
  and data
• Objects are an Abstraction
• represent real world entities
• Classes are data types that define shared common
  properties or attributes
• Objects are instances of a class
• All objects have attributes (characteristics),
  this is sometimes referred to as state.
• Objects have State
• have a value at a particular time
• Objects have Operations
• associated set of operations called methods that
  describe how to carry out operations (behavior)
• Objects have Messages
• request an object to carry out one of its
  operations by sending it a message
• messages are the means by which we exchange data
  between objects

4
Classes

• Class Whatever we can see in this world all the
  things are a object. And all the objects are
  categorized in a special group. That group is
  termed as a class.
• Class has many other features like creation and
  implementation of the object, Inheritance etc.

5
classes

• Every object belongs to (is an instance of) a
  class
• An object may have fields, or variables
• The class describes those fields
• An object may have methods
• The class describes those methods
• An Abstract Data Type (ADT) bundles together
• some data, representing an object or "thing"
• the operations on that data
• The operations defined by the ADT are the only
  operations permitted on its data
• Example a CheckingAccount, with operations
  deposit, withdraw, getBalance, etc.

6
Problem printing student mark sheet

• Class student
• Real world entities student, teacher, subject,
  mark sheet etc.
• Class student
• Public
• int RollNo
• string name
• string address
• void PrintDetails()
• cout ltltrollno
• cout ltltname
• cout ltlt address

7
TV-01 Class and 3 Instances
8
Object-Oriented Concept

• The rectangle area problem
• Define a class Rect
• Data width, length
• Functions compute_area()
• An object an instance of the class Rect
• To Solve the problem, create an object of Rect,
  and request this object to return the area of the
  rectangle

9
Encapsulation
class Circle private int radius public
Circle(int r) // The area of a circle int
compute_area()
class Triangle private int edgea, edgeb,
edgec public Triangle (int a, int b, int
c) // The area of a triangle int
compute_area()
10
Example Code
class Rect private int width,
length public Rect (int w, int l)
width w length l int
compute_area() return widthlength
main() Rect rect1(3,5) int
x xrect1.compute_area() coutltltxltltendl
11
Methods Messages

• Sending a message is our way of
• interacting with objects.
• manipulating an objects state.
• Tells the object what to do with itself
• Example To change the channel on TV
• We use the channel selection buttons ,This
  sends a message that we want to select a new
  channel
• The TV responds to the message by selecting
  and executing a method.
• The TV now receives a new signal which is the
  channel we selected

12

• Method
• Tells the object how to respond to a message
• Our TV-01 objects respond to the
• following messages
• Turn the television set on or off
• Change the channel
• Change the volume

13
(No Transcript)
14
Characteristics of OOPL

• Encapsulation Combining data structure with
  actions
• Data structure represents the properties, the
  states, or characteristics of objects
• Actions permissible behaviors that are
  controlled through the member functions
• Data hiding Process of making certain data
  inaccessible
• Inheritance Ability to derive new objects from
  old ones
• permits objects of a more specific class to
  inherit the properties (data) and behaviors
  (functions) of a more general/base class
• ability to define a hierarchical relationship
  between objects
• Polymorphism Ability for different objects to
  interpret functions differently

15
O-O Principles and C Constructs

• O-O Concept C Construct(s)
• Abstraction Classes
• Encapsulation Classes
• Information Hiding Public and Private Members
• Polymorphism Operator overloading,
• templates, virtual functions
• Inheritance Derived Classes

16
OOP Features

• 4 major features in OOP
• encapsulation
• information hiding
• inheritance
• overloading

17
Encapsulation

• an object encapsulates both its attributes
  methods
• implications
• an attribute/ method is attached to an object/
  class
• when you mention an attribute/ methods, you have
  to specify which object/ class it comes from
• why encapsulation?
• when you get hold of an object, you also get hold
  of its data behaviour components
• good for reuse

18
Information Hiding

• an object can hide its internal details
• e.g. you dont know how your mobiles electronics
  works except punching the buttons
• can selectively show some details to the outside
  world
• e.g. your mobile only shows the number it dials
• defines an interface to interact with the
  outside world
• e.g. your mobile interacts with your through the
  buttons screen

19
Why Information Hiding?

• the object can have a complex internal but simple
  interface
• making interaction with the outside world easier
• you dont need to know about the internal of an
  object
• only the interface is important
• i.e. how to interact with it
• facilitate code reuse
• hiding any internal change from the outside world
  by keeping the interface unchanged

20
Inheritance

• a class may be similar to another class but being
  more specialised
• e.g. the class student is similar to the class
  person but student is more specialised
• a person has attributes like sex, age, name
• a student has all these a student no.

21
Inheritance (contd)

• a subclass
• extends/ specialises a superclass
• inherits attributes methods from its superclass
• may have more attributes/ methods than its
  superclass
• may change the content/ procedure of an inherited
  method
• i.e. same method name/ signature but different
  behaviour
• why inheritance?
• reuse existing class definition
• customise/ specialise if needed

22
Overloading

• different functions/ procedures/ methods can have
  the same name
• provided that the parameters are of different
  types
• giving a unique signature
• the system will figure out which one to invoke
• e.g. you can have 2 procedures, both named
  call, taking a dog or person object as
  parameter respectively. Depending on you give it
  a dog or person object as the parameter, Java
  will know which one to use.

23
Why Overloading?

• you can call the same method (name) but invoke
  different behaviour
• dynamic binding of method
• which method to invoke is determined at runtime
• code reuse
• in term of the calling code

24

• Encapsulation is the mechanism that binds
  together code and data, and keeps both safe from
  outside interference or misuse.1. Both data and
  member functions treated as single unit2.
  Abstract focuses on behavior of object,
  encapsulation focuses on actual implementation
  3. Encapsulation achieved through data hiding
  4. For abstractions to work, implementations
  must be encapsulated.

25
Abstract Types
class Shape public Shape() //
Calculate the area for // this shape virtual
int compute_area() 0
26
ABSTRACTION AND ENCAPSULATION
?? Definition Data Encapsulation or Information
Hiding is the concealing of the implementation
details of a data object from the outside
world. ?? Definition Data Abstraction is the
separation between the specification of a data
object and its implementation. ?? Definition A
data type is a collection of objects and a set of
operations that act on those objects. ??
Definition An abstract data type (ADT) is a data
type that is organized in such a way that the
specification of the objects and the
specification of the operations on the objects is
separated from the representation of the
objects and the implementation of the operation
27

• Advantages of Data Abstraction and
• Data Encapsulation
• ?? Simplification of software development
• ?? Testing and Debugging
• ?? Reusability
• ?? Modifications to the representation of a data
  type

28
Abstract Classes May Contain abstract
methods Some methods and data may be
defined abstract class ColouredShape private
Colour c // storage allocated for each public
abstract void draw() public Colour getColour()
return c public abstract void erase()
No instances allowed Subclasses must implement
all abstract methods or they are also abstract
29
Florida Community College at Jacksonville

• Object-oriented Principle -
  Inheritance
• Inheritance is the process by which one object
  acquires the properties of another object. By use
  of inheritance, an object need only define all of
  its characteristics that make it unique within
  its class, it can inherit its general attributes
  from its parent.

Account
Checking
Mortgage
Loan
29 of 10 slides
COP 2551 Object-Oriented Programming OO
Concepts Overview
30
Florida Community College at Jacksonville

• Object-oriented Principle Encapsulation
• Encapsulation is the mechanism that binds
  together the code and the data it manipulates,
  and keeps both safe from outside interference and
  misuse.

A Class
Public variables and methods
Private variables and methods
Public variables is not recommended
30 of 10 slides
COP 2551 Object-Oriented Programming OO
Concepts Overview
31

• Encapsulation
• Hides the implementation details of a class
• Forces the user to use an interface to access
  data
• Makes the code more maintainable
• API doc as an example

32
Inheritance and Polymorphism
class Circle public Shape private int
radius public Circle (int r) int
compute_area()
class Triangle public Shape private int
edgea, edgeb, edgec public Triangle (int a,
int b, int c) int compute_area()
int sum_area(Shape s1, Shape s2) return
s1.compute_area() s2.compute_area() //
Example of polymorphism
33
INTRODUCTION TO C

• Inherit all ANSI C directives
• Inherit all C functions

34
Basic C Extension from C

• comments
• / You can still use the old comment style, /
• / but you must be very careful about mixing them
  /
• // It's best to use this style for 1 line or
  partial lines
• / And use this style when your comment
• consists of multiple lines /
• cin and cout (and include ltiostream.hgt)
• cout ltlt Hello"
• char name10
• cin gtgt name
• cout ltlt Hi, " ltlt name ltlt ", nice name." ltlt endl
• cout ltlt endl // print a blank line
• declaring variables almost anywhere
• // declare a variable when you need it
• for (int k 1 k lt 5 k)
• char am
• cout ltlt k ltlt a

35
CLASSES
36
A Graphical Representation of Classes
the Dog class
the Person class
attributes (data component)
colour name where
name own
interface to the outside world
walk instruct write_email
walk swim bark
methods (procedural component)
37
A Graphical Representation of Objects
Paki, a Dog object
Lassie, a Dog object
Ravi, a Person object
colour yellow name Paki where xxx
colour white/brown name Lassie where Annur
name Ravi own Lassie
walk swim bark
walk instruct write_email
walk swim bark
, another Dog object
Raja, a Person object
nameRaja own null
, another Dog object
, another Person object
walk instruct write_email
38
Access specifiers

• Specify whether the data defined will be
  available to the users of the objects of the
  class.
• Public
• Private
• Protected
• Public the data defined under public is
  available to objects.
• Private data defined under private is not
  available to objects.

39

• Class student
• Public
• int RollNo
• private
• string name
• string address
• public
• void PrintDetails()
• cout ltltrollno
• cout ltltname
• cout ltlt address
• void main()
• student student1

40
Function and data member

• Functions can be defined either inside or outside
  the class.
• Defining function members outside class
• very simple to define functions outside class
• If the functions are bigdefine outside
• Static data members of class
• Static members are stored at a location where
  they are retained throughout the execution of the
  program and are not stored with class objects.
• Stored only as a single copy similar to member
  functions.
• All the static data members are initialized to
  zero at the time of declaration.

41

• Class student //defining function
  members outside class
• Public
• int RollNo
• string name
• string address
• void PrintDetails() //prototype
• void student PrintDetails()
• cout ltltrollno
• cout ltltname
• cout ltlt address
• void main()
• student student1

42

• class student
• public
• static int PassingMark
• int SubjectMark5 bool fail
• void DisplayMarks()
• for (int i0ilt5i)
• cout ltltMarks of subject
  No.
• cout ltltiltltis
  ltltSubjectMarki
• void SetMarks (int Marks5
• for (int i0 ilt5 i)
• 
  SubjectMarksiMarksi
• bool CheckPassing()
• failfalse
• for (int i0ilt5 i)
• if (SubjectMarkiltPassi
  ngMark)

43

• int student PassingMark
• //required definition
• void main()
• studentPassingMark35
• student X
• student Y
• int Xmarks75,55,65,56,89
• int Ymarks15,25,100,98,89
• X.SetMarks(Xmarks)
• Y.SetMarks(Ymarks)
• X.CheckPassing()
• Y.CheckPassing()

44
Default Arguments

• A default argument is a value given in the
  function declaration that the compiler
  automatically inserts if the caller does not
  provide a value for that argument in the function
  call.
• Syntax

return_type f(, type x default_value,)
45
Default Arguments (Examples)

• The default value of the 2nd argument is 2.
• This means that if the programmer calls pow(x),
  the compiler will replace that call with
  pow(x,2), returning x2

double pow(double x, int n2) // computes and
returns xn
46
Default Arguments (Rules)

• Once an argument has a default value, all the
  arguments after it must have default values.
• Once an argument is defaulted in a function call,
  all the remaining arguments must be defaulted.

int f(int x, int y0, int n) // illegal
int f(int x, int y0, int n1) // legal
47
Function overloading

• Function redefined with different set of
  arguments.
• EX
• add(float, float)
• Add(int, int)
• Add (int, int, int)
• Function overloading is useful when similar
  function is required to be called with either
  variable number of arguments or arguments of
  different type or both.

48
Function Overloading

• Two or more functions can have the same name but
  different parameters
• Example

int max(int a, int b) if (agt b) return
a else return b
float max(float a, float b) if (agt b) return
a else return b
49

• What is a Friend Function?
• A friend function is used for accessing the
  non-public members of a class. A class can allow
  non-member functions and other classes to access
  its own private data, by making them friends.
  Thus, a friend function is an ordinary function
  or a member of another class.
• How to define and use Friend Function in C
• The friend function is written as any other
  normal function, except the function declaration
  of these functions is preceded with the keyword
  friend. The friend function must have the class
  to which it is declared as friend passed to it in
  argument.
• Some important points
• The keyword friend is placed only in the function
  declaration of the friend function and not in the
  function definition.
• It is possible to declare a function as friend
  in any number of classes.
• When a class is declared as a friend, the friend
  class has access to the private data of the class
  that made this a friend.
• It is possible to declare the friend function as
  either private or public.
• The function can be invoked without the use of an
  object.

50
Friend function

• class class1privateint numpublicvoid
  get()coutltlt"Number"cingtgtnumfriend void
  display(class1 cl)void display(class1
  c1)coutltltC1.NUMint main()class1
  clscls.get()display(cls)

51

• //static member friend function matrix
  multiplication
•  
• includeltiostream.hgt
• includeltconio.hgt
•  
• class matrixvector
• static int a33
• static int b3
• static int c3
• public
• void getmatrix(void)
• void getvector(void)
• friend int multiply(matrixvector mv)
•  
• int matrixvectora33
• int matrixvectorb3
• int matrixvectorc3

52

• void matrixvectorgetvector(void)
• coutltlt"\n"
• coutltlt"\n enter the vector "
• for(int k0 klt3k)
• cingtgtbk
•  
• int multiply(matrixvector mv)
• coutltlt"matrix - vector multiplication \n"
• coutltlt"\n the vector \n"
•  
• for(int m0mlt3m)
• coutltlt"\n"
• coutltltmv.bm

53

• coutltlt"\n"
• for(int e0elt3e)
• for(int d0dlt3d)
• mv.cemv.cemv.aedmv.bd
• coutltlt"\n the result is \n"
• for(int n0nlt3n)
• coutltltmv.cn
• coutltlt"\n"
• return 0
•  int main()
• clrscr()

54
const member functions

• A function, which guarantees not to modify the
  invoking object.
• If the body of the const function contains a
  statement that modifies the invoking object, the
  program does not compile.
• One exception here is the mutable member. A
  mutable data member can be modified by const
  function.

55

• void PrintDetails()const
• cout ltltrollno
• cout ltltname
• cout ltlt address
• rollno4 //error
• If rollno definition is changed to
• mutable int rollno
• in the student class ,then there will not be an
  error.

56
Volatile functions

• A member function invoked by a volatile object.
• A volatile object s value can be changed by
  external parameters which are not under the
  control of the program.

57

• volatile member functions. Declare a member
  function with the volatile specifier to ensure
  that it can be called safely for a volatile
  object
• class B
• int x
• public
• void f() volatile // volatile member
  function
• int main()
• volatile B b // b is a volatile
  object
• b.f() // call a volatile
  member function safely
• The object b is declared volatile. Calling a
  non-volatile member function from this object is
  unsafe, because b's state might have been changed
  by a different thread in the meantime.
• To ensure that f() can be called safely for a
  volatile object, it's declared volatile too.

58
Pointers and objects
int x 10 int p p x p gets the
address of x in memory.
p
x
10
59
What is a pointer?
int x 10 int p p x p 20 p is
the value at the address p.
p
x
20
60
What is a pointer?
Declares a pointer to an integer
int x 10 int p NULL p x p 20
is address operator gets address of x
dereference operator gets value at p
61
Allocating memory using new

• Point p new Point(5, 5)
• new allocates space to hold the object.
• new calls the objects constructor.
• new returns a pointer to that object.

62
Deallocating memory using delete

• // allocate memory
• Point p new Point(5, 5)
• ...
• // free the memory
• delete p
• For every call to new, there must be
• exactly one call to delete.

63
Using new with arrays

• int x 10
• int nums1 new int10 // ok
• int nums2 new intx // ok
• Initializes an array of 10 integers on the heap.

64

• A pointer can point to an object created by a
  class.
• Object pointers are useful in creating objects at
  run time.
• student s1
• student ptr s1
• s1. getdata()
• s1.show() equivalent to ptr-gtgetdata()
• 
  ptr-gt show() or
• 
  (ptr).show()
• we can also create the objects using pointers
  and new operator
• student ptr new student
• This allocates enough memory for the data members
  in the object structure and assigns the address
  of the memory space to ptr.
• We can also create an array of objects using
  pointers.
• student ptr new student5

65
constant objects

• const student s1(x,y) // object s1 is
  constant
• Any attempt to modify the values of x and y will
  generate compile time error.
• A constant object can call only constant member
  functions.
• void PrintDetails()const
• cout ltltrollno
• cout ltltname
• cout ltlt address

66
nested classes

• It is an another way of inheriting properties of
  one class into another.
• From this we can understand that an object can
  be collection of many other objects, that is a
  class can contain objects of other classes as its
  members .
• class alpha()
• class beta()
• class gamma
• alpha a1
• beta b1
• All objects of gamma class will contain the
  objects a1 and b1. This kind of relationship is
  called containership or nesting.

67
local classes

• Classes can be defined and used inside a function
  or a block. Such classes are called local
  classes.
• void test(int a) //function
• ..
• class student //local
  class
• ..
• ..
  //class definition
• student s1(a) //create
  student object
• .
• Local classes can use global variables and
  static variables declared inside the function.
• Enclosing function cannot access the private
  member of a local class.

68
Basic C Extension from C (II)

• const
• In C,define statements are handled by the
  preprocessor, so there is no type checking.
• In C, the const specifier is interpreted by the
  compiler, and type checking is applied.
• New data type
• Reference data type . Much likes pointer
• int ix / ix is "real" variable /
  
• int rx ix / rx is "alias" for ix /
• ix 1 / also rx 1 /
• rx 2 / also ix 2 /

69
C - Advance Extension

• C allow function overloading
• In C, functions can use the same names, within
  the same scope, if each can be distinguished by
  its name and signature
• The signature specifies the number, type, and
  order of the parameters
• The name plus signature, then, uniquely
  identifies a function

70
Take Home Message

• There are many different kinds of programming
  paradigms, OOP is one among them.
• In OOP, programmers see the execution of the
  program as a collection of dialoging objects.
• The main characteristics of OOPL include
  encapsulation, inheritance, and polymorphism. Not
  only OOPL can do OOP, but also others.