C++ Static Data Member

• A data member of a class can be qualified as static. It has certain special characteristics.
• It is initialized to zero when the first object is created.
• Only one copy of that member is created for the entire class and is shared by all the objects of that class.
• It is visible only within the class, but its lifetime is the entire program.
• Static variable are normally used to maintain values common to the entire class.
• The type and scope of each static member variable must be defined outside the class definition. This is necessary because the static members are stored separately rather than as a part of an object.
• They are associated with the class it self rather than with any class object, they are also known as class variable.

Example:

#include <iostream.h>

#include<conio.h>

class student

{

private: static int code; //data member

int rollno;

public: static void init (int c) //data member function

{

code=c;

}

void getdata (int r)

{

rollno =r;

}

void show()

{

cout<<“Rollno = “<<rollno<<endl;

cout<<“Code = “<<code<<endl;

}

};

int student :: code;

void main ()

{

clrscr();

student :: init (108);

student obj1,obj2;

obj1.getdata(448);

obj2.getdata(224);

obj1.show();

obj2.show();

getch();

}