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Saturday, November 11, 2017

C++ programming language part: 52 Inheritance


  Inheritance


The way to reuse existing software to create new software is by means of inheritance also called specialization or derivation. It is an important feature of object-oriented programming. The most important of them being the reusability of code. Once a class is defined and debugged, it can be used to create new subclass. The class from which another class has been derived is called the base class The class that inherits the properties of the base class is called the derived class. The derived class override some or all the properties of the base class. An object defined outside the class can access only the public member of the class. Therefore, private members of a class cannot be directly accessed from outside the class. The protected members of a class can be accessed by its member function, or within any class derived from it. Protected members behave like public members with respect to the derived class, and like private members with respect to the rest of the program.
The common syntax for deriving a class Y from a class X is: class Y:public X

Program 42_1
//inherit.demo
            class furniture              //class defined
            { protected:
              char color[10];
              int width,height;
            };
            class bookshelf:public furniture
            {  private:
               int self_no;               // member data
               public:
               void data_in()
             {
               cout<<"Type color of bookshelf (red or blue?)\t";
               cin>>color;
               cout<<"Type width\t";
               cin>>width;
               cout<<"Type height\t";
               cin>>height;
               cout<<"Type number of selves\t";
               cin>>self_no;  }
             
               void data_out() //member function
            { cout<<" The color is "<
              cout<<" The width is "<
              cout<<" The height is "<
              cout<<" Number of selves is "<
            };
            class chair:public furniture
            { private:
               int leg_no;                
               public:
             



  void data_in()      //member function
              {cout<<"Type color of chair (yellow or black?)\t";
               cin>>color;
               cout<<"Type width\t";
               cin>>width;
               cout<<"Type height\t";
               cin>>height;
               cout<<"Type number of legs\t";
               cin>>leg_no;  }
             
               void data_out() //member function
            {cout<<" The color is "<
             cout<<" The width is "<
             cout<<" The height is "<
             cout<<" Number of legs is "<
            };

void main()
            {bookshelf A;    // k is called object
             chair B;
             A.data_in();                //would be k->data_in() if pointer
             A.data_out();
             B.data_in();                 //would be k->data_in() if pointer
             B.data_out(); }


Keyword Size Of

Program 42_extra
          { char a1[10],a2[10];//array of size 10 defined
            char *a3;          //[20];  
            int i,j;
            a3=new char[20];
            cout<<"type the  string "<<"\n";
            cin>>a1;
            cout<<"type another string "<<"\n";
             cin>>a2;
            for(i=0;a1[i];i++)
            a3[i]=a1[i];
            for(j=0;a2[j];j++,i++)
            a3[i]=a2[j];
            a3[i]='\0';
            cout<<"The marged string is "<

            cout<<" The size of strings= "<




Part- 86 assign the content of twostring



জ্ঞানকোষ প্রকাশনী
৩৮/২-ক, বাংলাবাজার (২য় তলা), ঢাকা।
       ফোনঃ ৭১১৮৪৪৩, ৮১১২৪৪১, ৮৬২৩২৫১.         
                                                     
কলকাতায় পরিবেশক/প্রাপ্তিস্থান
রিতা ইন্টারন্যাশনাল
৩৬, পি.এন. ব্যানার্জি রোড, কলকাতা
ফোনঃ ২৫১৩৮৩৫৯, ৯৮৩০৪৩৯৬৭৯, +৯১৯৮৩০৪৩৯৬৭৯


C++ programming language part: 53 Overriding Base Class Members


Overriding Base Class Members

A base class member can be overridden by defining a derived class member with the same name. But the member of derived class have the same signature as those in base class.

Program 42_2
            class a_base                 //class defined
            { public:
               void display()
             {cout<<"This is bass class \n"; }
   int x;
             };
           
 class b_derived:public a_base
            { public:
               void display()           // the same name as base class
            { cout<<"This is derived class \n"; }
               int x;
            };
           
 void main()
{
 a_base A;
 A.display();
 A.x=20;
 cout<<"the A.x =  "<
 b_derived B;                           // B is called object
 B.display();                 //would be B->display() if pointer
 B.x=40;
 cout<<"the A.x = "<
 // A.a_base::x=60;
 // cout<<"the A.a_base::x= "<
 B.a_base::x=60;
 cout<<"the B.a_base::x= "<
 a_base c=A;
 cout<<"the c.x = "<

 }






জ্ঞানকোষ প্রকাশনী
৩৮/২-ক, বাংলাবাজার (২য় তলা), ঢাকা।
       ফোনঃ ৭১১৮৪৪৩, ৮১১২৪৪১, ৮৬২৩২৫১.         
                                                     
কলকাতায় পরিবেশক/প্রাপ্তিস্থান
রিতা ইন্টারন্যাশনাল
৩৬, পি.এন. ব্যানার্জি রোড, কলকাতা
ফোনঃ ২৫১৩৮৩৫৯, ৯৮৩০৪৩৯৬৭৯, +৯১৯৮৩০৪৩৯৬৭৯