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Data Structure and Algorithm CIT231

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					Data Structure and
Algorithm: CIT231
           Lecture 4:
 ADT and Introduction to Object
  Oriented Programming (OOP)

         Bajuna Salehe
      bajunar@yahoo.com
Introduction to Object
Oriented Programming
   In this lecture you will learn the general
    concepts of Object Oriented Programming
    (OOP).
       Inheritance
       Encapsulation
       Polymorphism
   Object Oriented Programming is very
    powerful and important programming
    paradigm.
Introduction to Object
Oriented Programming
   Most of the nowadays sophisticated
    application software have been developed in
    Objected Oriented languages and mostly in
    C++.
   E.g. Word processors, spreadsheets, and
    graphics applications.
   Also some Operating Systems are written in
    OO languages.
Fundamental terms and
Principles of the OOP
   Attribute – The data for a class that maintains
    the current state of an object. The state of an
    object is determined by the current contents
    of all the attributes.
   Object – An object is a something that exists
    and is identifiable. An object exhibits
    behaviour and maintains state. Example of
    objects are telephones, automobiles,
    buildings, animals, etc.
Fundamental terms and
Principles of the OOP
   Class – Class is a synonymous with type. A
    class specifies a traits (data) and behaviour
    that an object can exhibit.
       A class itself does not exists. It is only a
        description of an object. A blueprint is analogous
        to a class and building itself is the object.

       A class can be considered a template for the
        creation of objects.
Fundamental terms and
Principles of the OOP
   Inheritance – This is the relationship of
    classes. There is an explicit is-a relationship
    between classes. For example an automobile
    is-a vehicle, a zebra is-a mammal, a flower
    is-a plant, and so on.
   Interface – The visible functionality of a
    class. Is the contract an object makes with
    users of an object. Users manipulate an
    object through its interface.
Fundamental terms and
Principles of the OOP
-   Interface of a class is the part the clients see.
    An interface is considered a contract the
    class has with its client.
-   For example an automobile has an interface
    (contract) with its driver. An automobile’s
    interface includes a steering wheel, brake
    pedals, speedometer, and a clutch.
-   This interface provides functionality to the
    driver without the need to know the inner
    workings of the automobile.
Fundamental terms and
Principles of the OOP
   Implementation – The internal functionality
    and attributes of a class. A class’s
    implementation is hidden from users of the
    class.
   Encapsulation – Encompasses the
    interfaces and abstraction of a class.
   Abstraction – The generalisation of a class
    that distinguish it from other classes
Fundamental terms and
Principles of the OOP
   Understanding inheritance is a good starting
    point of learning object orientation.

   The concept of inheritance can be
    understood in analog to your family tree.

   The procedure to describe your family tree is
    the same to describe class inheritance in
    C++.
Fundamental terms and
Principles of the OOP
   Inheritance is known as an is-a relationship.
    Example a toyota is-a vehicle, a snake is-a
    reptile, and a flower is-a plant.
   To begin applying inheritance, you must
    decide a base class that must reside within
    your application. It provides basic, default
    functionality to users of the class.
Access Specifier of the class
   The class in C++ contains three important
    access specifiers which provide conditions to
    access to the data members and functions
    (methods) of the class.
   These are
       Public
       Private
       Protected
Access Specifier of the class
 Public – A class member with public
  visibility is accessible outside of the
  class.
 Private – A class member with private
  visibility can only be accessible by
  member functions of the class.
 Protected – A class member with
  protected visibility is accessible by
  member functions of the class and its
  descendents.
MATRIX Operation with the
use of Class
   #include <iostream.h>
   Const int MAX = 3;
   Class Matrix
   {
     Private:

       Int mat[MAX][MAX];
    Public:
       Matrix();
       void create ();
       void display ();
   };
Initialise Matrix()
Matrix::Matrix()
{
  for(int i=0; i<MAX; i++)
  {
    for (int j=0; j<MAX; j++)
    mat[i][j]=0;
  }
}
Create matrix()
//Create matrix mat
Void Matrix::create()
{
   int n;
  for (int i=0; i<MAX; i++)
     {
     for (int j = 0; j<MAX; j++)
      {
        cout<<“Enter the element: ”;
        cin>>n;
        mat[i][j] = n;
      }
   }
}
Display matrix()
//displays the contents of the matrix
Void Matrix::display();
{
  for (int i=0; i<MAX; i++)
  {
   for (int j=0; j<MAX; j++)
    cout<<mat[i][j]<<“ ”;
    cout<<endl;
  }
}
Create the object of Matrix in
the Main program
void main()
{
  matrix mat1;
  cout<<"\nEnter the elements of the array: \n";
  mat1.create();

    cout<<"Your array is:\n";
      mat1.display();
}
Pointers
   A pointer is a variable which stores the
    address of another variable.
   There are two important operators when
    working with pointers in C++:
       the address of (&) operator
       the value of (*) operator
   How much storage space does a pointer
    consume? Use sizeof(ptr) without the '*‘
    operator to determine the memory utilised on
    your system
Pointers
   Irrespective of datatype or whether the
    pointer points to a single variable or array, as
    a general rule, pointers must use the same
    amount of memory space.
   The & operator gives us the address of a
    variable and * gives us the value of a variable
    at a specified address. Example:-
Example of the use of * and &
   #include <iostream.h>
   #include <stdlib.h>

   int main()
   {
          int i = 10;

       cout << "The value of variable i is " << i << "\n";

       cout << "The memory address of i is " << &i << "\n";
       /*
            Prints the memory address in hexadecimal format

       */

       cout << "The value of variable i using * operator is "<< *(&i) <<"\n";
       /*
             The * operator gives the value when provided with a memory address. Note
          that the dsta type is inferred from the variable name.
       */
       system("PAUSE");
       return 0;
   }
    Pointer Example
   #include <iostream.h>
   #include <stdlib.h>

   int main()
   {
     int i = 10;
     int *x = &i;
     int *y;
     /*
       x stores the address of variable i. Pointer assignment could also be done as
     */
     y = &i;

       cout <<"The pointer x is stored at the mempory address "<< &x << "\n";
       cout <<"The pointer x stores the memory address of i: " << y << "\n";

       /*
                                Contrast the difference between the memory address of the pointer
            and the memory address it stores.
       */

       cout<< "The value of i accessed through pointer x is " << *x << "\n";

       /*
                                  Now we manipulate the value of i using pointer x;
       */

       *x = *x + 1; // increment i by 1

       cout<< "i (through pointer) = " << *x << " which equals i (direct access) " << i << "\n";
       /*
                                 A pointer does not create a copy of the variable it points to.
       */

       cout<<"The memory allocated to the pointer x is " << sizeof(x) << " bytes. ";
       system("pause");
       return 0;

   }
Array as Pointers
   In C++ array starts at position 0.
   The elements of the array occupy adjacent
    locations in memory.
   C++ treats the name of the array as if it was
    the pointer to the first element.
   If v is an array, *v is the same thing as v[0],
    *(v+1) is the same thing as v[1] as diagram
    below shows:
Array as Pointers
   Pointer use for an array
Exercise
   Using matrix arrays, write a program to
    create two matrices and then create methods
    of adding and subtracting those matrices.
Next Topic
   String ADT and array of characters

				
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