Static Data Members

To create a static data member only you have to proceed a member variables declaration with static keyword.

All static variables are automatically to zero value , when the first object of the class is created. No other initialization is permitted.

Only one copy of static data member is created for the entire class and is shared by the objects of that class.

Since static variables are associated with the class itself rather than object called as class variables.

static data member is visible only within the class but lifetime is entire program.

The type and scope of each static data member must be redefined outside the class definition because static data member are stored separately rather than as a part of object.


Syntax:

Data_type classname :: static_variable_name;
            The static variable must be declared in a class with a keyword static.

Write a Program to count the no of objects using static data member.

#include<iostream.h>
#include<conio.h>
class item
{
static int count;
public:
void getdata( )
{
count++;
}
void display( )
{
cout<<"\n\n\tNo of object count is--->"<<count;
}
};
int item::count;
void main( )
{
item x1,y1,z1;
x1.getdata( );
y1.getdata( );
z1.getdata( );
cout<<"\n\n\tAfter Reading Data is--->";
x1.display( );
y1.display( );
z1.display( );
getch( );
}


Output:-
    After Reading Data is--->
    No of object count is--->3
    No of object count is--->3
    No of object count is--->3