Q. Define class and object with example and explain diverse specifies.
OR
Describe the class differentiate the public and private members of the class. Also describe the method to access the private and public members of the class.
Ans. Classes: A class is a group of objects that share general characteristics and relationship. It presents a group of identical objects. The complete set of data and code of an object can be made a user defined data type with the aid of a class. Objects are variables of the category class. In other words objects consists of data, and code to change the data. The complete set of data and code of an object can be made of a user defined data type with the aid of a class. Actually, objects are variables of the category class. Once a class has been stated and clear, we can develop any number of objects related to that class. Each object is related with the data of type class with which they are developed. A class is therefore a group of objects of identical type. For instance, apple, mango and orange are parts of the class fruit. Classes are user defined data types and act like the built in tyres of programming language. The syntax utilized to develop an object is no distinct than the syntax used to develop an integer object in C. If fruit has been defined as a class, then the statement
Fruit mango;
Will create an object mango belonging to the class fruit.
A simple class example
A typical class declaration would look like:
Class item
{
Int number; // variables declarations
Float cost; // private by default
Public:
Void get data (Int a, float b); // functions declarations
Void put data (void); // using prototype
// ends with semicolon
};
Distinction between public and private: The differences are given in the tabulated form:
|
Members of base class (visibility)
|
members
|
Of derived
class
|
(visibility)
|
|
|
public derivation
|
private derivation
|
Protected derivation
|
|
private
|
Not inherited
|
Not
inherited
|
Not
inherited
|
|
protected
|
protected
|
Private
|
protected
|
|
Public
|
Public
|
private
|
protected
|
Accessing private members:
. Private data type only:-
# include < iostream.h >
Class item
{
Int number; // private by default
Float cost; // private by default
Public:
Void get data (Int a, float b); // prototype declaration,
// to be defined
// function defined inside class
Void put data (void)
{
Cout << "number:" << number << "\n";
} cout << "cost :" << cost << "\n";
};
//..............................member function definition.....................................................
Void item :: get data (Int a, float b) // use membership label
{
Number = a; // private variables
Cost = b; // directly used
}
//.............................main programme...................................
Int main 0
{
Int main 0
{
Item x;
Cout << "\n object x" << "\n";
X get data (100299.95); // call member function
X. put data 0; call // member function
Item y; // create another object
Cout << "\n object y" << "\n";
y. get data (200, 175.50);
y. put data 0;
Return 0;
}
The object of the programme would be:
Object x
Number: 100
Cost : 299.95
Object y
Number: 200
Cost : 175.5
Prime member function: A private member function can only be called as an added function that is a part of its class. Even an object cannot appeal to a private function with the use of the dot operator. Assume a class as defined below:
Class sample
{
Int m;
Void real (void); // private member function
Public :
Void up date (void);
Void write (void);
If s 1 is an object of sample, then
S 1.read (); // would not work; objects cannot access
// private members
is illegal. Though the function read 0 can be called by the function up date 0 to update an object to update the value of m.
Void sample:: update (void)
{
Read 0; // simple call; no object is used
}