Object oriented programming slides for presentation

Presentation

1. Object Oriented Programming W7 - L7 02/08/2024

2. Pointers Overview: Variable & MEMORY Computer memory is a collection of different memory locations. These memory locations are numbered sequentially. Each variable is created at a unique location in memory known as its address. A program may declare many variables. A variable declaration reserves specific amount of space in memory for a particular variable. The variable name is used to refer to that memory location. It allows the users to access a value in the memory. The computer refers to the memory using address. 02/08/2024

3. When we declare a variable three things are associated with that variable Variable name Variable type Variable address 02/08/2024

4. Example: Int main() { Int a; Cout << “The address of a is: ” << &a; Return 0; } 02/08/2024

5. Can we store address of variable in another variable? 02/08/2024 Int main() { Int a; Int b; B = &a Cout << “The address of a is: ” << &a; Return 0; }

6. Pointer A pointer is a variable that is used to store a memory address. WHY we need Memory address when we can use variable with their names? Pointers can access and manipulate data in computer memory directly 02/08/2024

7. Advantages of Pointer: It can access the memory address directly. It can save memory It runs faster as it doesnot duplicate data. 02/08/2024

8. Example: Int main() { Int n ; Int * ptr ; Cout << “enter an integer” ; Cin >> n ; Ptr = &n; Cout << “the value of n is” << n ; Cout << “the address of n” << ptr ; Return 0; } 02/08/2024

9. Void pointer( A void pointer is a pointer that has no associated data type with it. A void pointer can hold address of any type and can be typecasted to any type ) // find output Int main() { Int a = 10; Float b = 10.5; Char c = ‘a’ ; Int * ptr ; Ptr = &a; Cout << “address stored in pointer is : ” << ptr ; } 02/08/2024

10. Find Error?? 02/08/2024 Int main() { Int a = 10; Float b = 10.5; Char c = ‘a’ ; Int * ptr ; Ptr = &b; Cout << “address stored in pointer is : ” << ptr ; }

11. Void Pointer 02/08/2024 Int main() { Int a = 10; Float b = 10.5; Char c = ‘a’ ; void * ptr ; Ptr = &a; Cout <<“value of a is:” << a; Cout << “address stored in pointer is : ” << ptr ; } Ptr = &b; Cout <<“value of b is :” << b; Cout << “address stored in pointer is : ” << ptr ; Ptr = &c; Cout <<“value of c is :” << c; Cout << “address stored in pointer is : ” << ptr ;

12. Output: 02/08/2024

13. Dereference Operator: ( * ) In computer programming, a dereference operator, also known as an indirection operator, operates on a pointer variable. It returns the location value, in memory pointed to by the variable's value . 02/08/2024

14. Example: Int main() { Int a = 20 ; Int * ptr ; Ptr = &a; Cout << the value stored in pointer is: “ << * ptr ; } 02/08/2024

15. Output : the value stored in pointer is: 20 02/08/2024

16. Data manipulation using Pointers Int main () { Int a , b , s , *p1, *p2 ; P1 = &a ; P2 = &b; Cout << Enter an Integer : “ ; Cin >> *p1; Cout << Enter an Integer : “ ; Cin >> * p2; 02/08/2024 S = *p1 + *p2 ; Cout << “sum is : ” << s; }

17. This pointer To know the address of current object , we use this pointer. Used to distinguished our data members and local variables when both are declared with the same name. We identify the data member using this pointer 02/08/2024

18. Example: Class person { Int age ; String name ; Person( int age , string name) { Age = age ; //compiler confusion Name = name ; } 02/08/2024 Void printvalue () { Cout << “age” << age ; Cout << “name” << name ; } };

19. Int main () { Person a(45 , “ABC”); a.printvalue (); } 02/08/2024

20. Output: 02/08/2024 Garbage value

21. Solution : this Pointer Class person { Int age ; String name ; Person( int age , string name) { This ->Age = age ; This ->Name = name ; } } 02/08/2024 Void printvalue () { Cout << “age” << age ; Cout << “name” << name ; } };

22. Int main () { Person a(35 , “ abc ”); a.printvalue (); } 02/08/2024

23. Output : 3 5 abc 02/08/2024

24. Task: we have two data members num and ch. In member function setMyValues () we have two local variables having same name as data members name. Create display function to show both values. In such case if you want to assign the local variable value to the data members then you won’t be able to do until unless you use this pointer, because the compiler won’t know that you are referring to object’s data members unless you use this pointer. 02/08/2024

25. Solution: 02/08/2024 #include < iostream > using namespace std ; class Demo { private : int num ; char ch ; public: void setMyValues ( int num , char ch ) { this-> num = num ; this-> ch = ch ; } void displayMyValues () { cout << num << endl ; cout << ch ; } }; int main() { Demo obj ; obj.setMyValues (100, 'A'); obj.displayMyValues (); return 0; }

26. Polymorphism One name multiple forms Poly means many and morphism means forms The behaviour of the object can be implemented at rum time. Compile time polymorphism Function overloading / method overloading / constructor overloading / operator overloading 2. Run time polymorphism virtual function Pointer to objects: pointer can also refer to an object of a class. The member of an object can be accessed through pointers by using the symbol ->(member access operator) Ptr ->member 02/08/2024

27. Overview: // early binding compiler already knows which function to call Class A { Public: void show() { Cout << “base class” ; } }; Derived Class 02/08/2024 Class B: public A { Public: void show() { Cout << “Derived class” ; } }; Int main() { B obj ; Obj.show (); } Output:

28. Overview: // early binding Class A { Public: void show() { Cout << “base class” ; } }; Derived Class Base class 02/08/2024 Class B: public A { Public: void show() { Cout << “Derived class” ; } }; Int main() { B obj ; Obj.show (); Obj.A.show (); } Output:

29. Overview: // late Binding Class A { Public: void show() { Cout << “base class” ; } }; base class 02/08/2024 Class B: public A { Public: void show() { Cout << “Derived class” ; } }; Int main() { A * ptr ; A obj ; Ptr = & obj ; Ptr - > show() ; } Output:

30. Virtual Base class / Virtual Function : Key word virtual Virtual function is re defined in derived class. When a virtual function is defined in base class, then the pointer to base class is created. Now on the basis of type of object assigned the respective class function is called. This is also called run time polymorphism. 02/08/2024

31. Virtual Function A virtual function (also known as virtual methods) is a member function that is declared within a base class and is re-defined (overridden) by a derived class. When you refer to a derived class object using a pointer or a reference to the base class, you can call a virtual function for that object and execute the derived class’s version of the method. 02/08/2024

32. Example: Class B : public A { Public: Void show() { Cout << “Child Class B” ; } }; 02/08/2024 Class A { Public: Void show() { Cout << “parent Class A” ; } }; Class C : public A { Public: Void show() { Cout << “Child Class C” ; } };

33. Int main () { A obj1 ; B obj2 ; C obj3; A * ptr ; Ptr = &obj1 ; Ptr -> show() ; 02/08/2024 Ptr = &obj2 ; Ptr ->show(); Ptr = &obj3; Ptr ->show(); } Pointer can store address of child class , but with the same pointer if we want to access child class member that also exist in parent class , this will always call member function of parent class.

34. Output: 02/08/2024

35. Using virtual keyword: One function is providing multiple functionalities depends on which type of address , pointer is holding. 02/08/2024

36. Example: Class B : public A { Public: Void show() { Cout << “Child Class B” ; } }; 02/08/2024 Class A { Public: Virtual Void show() { Cout << “parent Class A” ; } }; Class C : public A { Public: Void show() { Cout << “Child Class C” ; } };

37. Int main () { A obj1 ; B obj2 ; C obj3; A * ptr ; Ptr = &obj1 ; Ptr -> show() ; 02/08/2024 Ptr = &obj2 ; Ptr ->show(); Ptr = &obj3; Ptr ->show(); }

38. Output: 02/08/2024

39. Working: When a member function is declared as a virtual in parent class and is called with pointer , the compiler checks the type of object referred by the pointer. It executes the member function according to the type of object not by type of pointer. The type of pointer in each call is different so the compiler executes different function each time. 02/08/2024

40. Binding: Binding refers to the process of converting identifiers (such as variable and performance names into addresses.) Binding is done for each variable and functions. For functions, it means that matching the call with the right function definition call by the compiler. Binding can be performed in two ways: Early binding/compile time binding/ static binding(As the name indicates compiler directly associate an address to the function call. In early binding, compiler knows at the time of compilation which block of code is to be executed upon a function call.) Late binding/ Dynamic binding(in late binding, compiler does not know at the time of compilation that which block of code is to be executed upon a function call. Late binding is attained by using virtual functions.) 02/08/2024

41. Early Binding Is also called compile time binding or static binding As the name indicates, compiler directly associate an address to the function call. In early binding , compiler knows at the time of compilation which block of code is to be executed upon a function call. 02/08/2024

42. Example: Early Binding 02/08/2024 Class A { Public: Void show() { Cout << “parent Class A” ; } }; Class B : Class A { Public: Void show() { Cout << “Derived Class B” ; } }; Int main() { B obj ; Obj.show (); Obj.A.show (); }

43. Late Binding In late binding compiler doesn’t know at the time of compilation that which block of code is to be executed upon a function call. Late binding is attained using virtual function . 02/08/2024

44. Example : Class parent { Public: Virtual void show() { Cout << “parent class” ; } }; 02/08/2024 Class child1: public parent { Public: void show() { Cout << “child1 class” ; } };

45. 02/08/2024 Class child2: public parent { Public: void show() { Cout << “child2 class” ; } };

46. Int main() { Parent * ptr [5] ; // array of pointers //This pointer can store address of child class address . Int op , i ; // for object creation Cout << “Enter 1 for parent , 2 for child1 & 3 for child2” ; } 02/08/2024

47. For (I = 0 ; I < 5 ; i ++) { Cout << “which object to create ?” ; Cin >> op ; If (op == 1) Ptr [ i ] = new parent ; // create new object of parent Else if (op ==2) Ptr [ i ] == new child1; Else (op ==3) Ptr [ i ] == new child2; } } 02/08/2024

48. For (I = o ; I <5 ; i ++) { Ptr [ i ] -> show(); It will call that function whose class object address is stored in pointer array. } 02/08/2024

49. 02/08/2024

50. What if we remove virtual keyword? What will be the output ?? 02/08/2024

51. Abstract class(Model class) and pure Virtual function No definition of virtual function assigned with zero. We can’t create the object of parent class having pure virtual function If we don’t override the function in child class that was present in abstract class then the child class will also become abstract class. 02/08/2024

52. Pure virtual function 02/08/2024

53. 02/08/2024 Output: Child1 class… Child2 class…