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Saturday, November 11, 2017

C++ programming language part: 50 Constructor


Constructor

Every object created would have a copy of member data. The above program, the object K of thwe class nova had to call a member function called data_in() , there is no possibility of member data getting initialize automatically. This automac initialization is performed through the use of constructor functions. So a constructor function is a special function that is a member of the class and has the same name as that of the class.

Program 40-1
            //class & object.demo
            #include
            #include

            class nova                    //class defined
            { private:
               int age;         // we can't type age=30,name[10]=bappi
               char name[10];       // so we need a 'constructor'
            public:
                           nova();                      //default constructor
               nova(int a, char* b);              // defined constructor
               void data_in();          // member function
               void data_out();
               };       
               nova::nova()
               {  cout<<" Look! It's invocked "<
               nova::nova(int a, char* b)   // constructor & class would be the same name
               { a=age;
                b=name;  }
            void nova::data_in()    //member function
               { cout<<" Type your age "<
                cin>>age;
                cout<<"Type your name "<
                cin>>name;  }
               void nova::data_out()           //scope resolution operator
               { cout<<" The age is "<
                  cout<<" The name is "<
               void main()
            {
             nova k;                       // k is called object
            k.data_in();                  //would be k->data_in() if pointer
             k.data_out();
             getch();
            }




 


Program 40_2
//class & object.demo
            #include
            #include

            class nova                    //class defined
            {
            private:
               int p1,p2,p3;   // we can't type p1=5 likk, need a 'constructor'
            public:
   nova();           //default constructor
               nova(int,int);              // defined constructor
               void data_in(int,int);       // member function
              void sum();
               void data_out();
               };       
               nova::nova()
               {  cout<<" Look! It's invocked "<
              p1=p2=p3=0;   }
               nova::nova(int x,int y)   // constructor & class would be the same name
               {  cout<<" two constructor are called "<
                p1=x;
                p2=y; }
            void nova::data_in(int a,int b)              //member function
               {
                p1=a;
                p2=b;
               }
               void nova::sum()
           {
           p3=p1+p2;
           }
               void nova::data_out()           //scope resolution operator
               {
                cout<<" The sum is= "<
               }
               void main()
               {
               nova k1,k2(4,3),*k3;                        // k is called object
               k3=new nova(5,10);  // new value are assign
               k2.sum();                  //this is from initialize member data
               k3->sum();
               k3->data_out();
           k2.data_out();

          }


Part- 86 assign the content of twostring



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