CLass and Object in C++ -1

Class is a way to bind data and its associated Function together .It also allows data and function to be hidden ,if necessary ,from External User .

The class Member that have been declare as private can be access only from within the class . on the other Hand Public data and function can be access from outside the class also .

By default the member of class is private . 

A simple Class Example :

1. class test{
2.                 //Private by default
3.                 int a;   //Variable declaration
4.                 float b;        
5.         public: //declaring public data and func
6.                 void assign(void); //declare member func
7.                 void print(void);
8. };
   

Creating An Object :

create a variable x of type "test" , In C++ Class variable is known as Object . Therefore  x is called an object of type "test" .

1.     test x,y,x  //declaring class object

Here x y and z is object of type test

Accessing Class Member :-

private data of Class can be access only through the member function of that Class.

Public data and function can be access using "."operator  

Example :

   object-name.function-name(actual arguments)

1.   test x; //create object
2. x.assign() //access function using . operator
3. x.print()

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Defining Class Member function :

It can be define inside or outside the class .

member function define inside is always inline ( you mention or not ) .

Defining Member Function outside Class .

  return-type class-name :: function-name(arguments){

        function body

} 

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A C++ Program With Class :

1. /*
2.  Introduction to class in C++
3.  http://beginer2cs.blogspot.com
4. */
5. #include<iostream>
6. using namespace std;
7. class test{
8.         private: //declaring private data
9.                 int a;
10.                 float b;       
11.         public: //declaring public data and func
12.                 void assign(void); //declare member func
13.                 void print(void);
14. };
15. /*
16.  "::" called Scope resolution operator
17. */
18. void test::assign(){ //defining member func
19.         int x;
20.         float y;
21.         cout<<"Enter value of a : ";
22.         cin>>x;
23.         cout<<"Enter value of b: ";
24.         cin>>y;
25.         a=x;
26.         b=y;
27. }
28. void test::print(){
29.         cout<<" a :- "<<a;
30.         cout<<"\n b :- "<<b;
31. }
32. main(){
33.         test x; //creating an object of class x
34.         x.assign(); //calling public func of class test
35.             /*we can't directly access private variable and data
36.               using "." operator . only public function of same
37.                   class can access it and modify it
38.                 */
39.         x.print();
40. }

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Output :