Static data members in C++ are shared across all objects of a class, initialized to zero upon class instantiation, and maintain values common to the class. They must be declared within the class and defined outside of it, functioning as class variables. Static member functions can access static members and are invoked using the class name.

1. Static Data Members and
Static member function

2. Static Data members
• Static member variable are similar to that of C static variable.
• Characteristic of static variable:
• It is initialized to zero when the first object of the class is created.
• Only one copy of that member is created for the entire class and it is
shared by all the objects of the class.
• It is visible only within the class, but its lifetime is the entire program.
• Static variables are normally used to maintain values common to the
entire class.

3. Definition of static data members
• static data_type data_member_name; // declaration
• type class name : : static datamember; // definition
• Eg: int item :: count;
• Static member variable must be defined outside the class definition.
They are also known as class variables.

4. • #include<iostream>
• using namespace std;
• class item
• {
• static int count;
• int number;
• public:
• void getdata(int a)
• {
• number=a;
• count++;
• }
• void getcount(void)
• {
•
cout<<count<<"n";
• }
• };
• int item::count;

5. • cout<<"after reading data"<<"
n";
• a.getcount();
• b.getcount();
• c.getcount();
• return 0;
• }
• int main()
• {
• item a,b,c;
• a.getcount();
• b.getcount();
• c.getcount();
• a.getdata(100);
• b.getdata(200);
• c.getdata(300);

6. Static Member functions
• Static member function can have access to other static
members( functions or variables) declared in the same class.
• Static member function can also be called using the class name
Class-name :: function-name;
• Just like a static variable once declared is allocated with memory that
can’t be changed every object points to the same memory.