23staticdatamem.cpp

#include <iostream>
using namespace std;

// While we use static variable in a class, it retains it's value and is shared among objects, i.e. all objects will have same static variable
class Employee
{
    int ID;
    static int count; // A static variable, also called class variable is already initialized by 0 and there is no need to manually initialize
public:
    void getData()
    {
        cout << endl
             << "Enter the Employee ID " << endl;
        cin >> ID;
        count++;
    }
    void setData()
    {
        cout << endl
             << "Employee " << count << " ID : [ " << ID << " ]" << endl;
    }
    static void countdisplay() // this is a static function which only accesses the static variables
    {
        cout << count << endl;
    }
};

int Employee ::count; // this is to initialize a static variable, defining its scope

int main()
{
    Employee Vasu, Dev, Aenansh;
    Vasu.getData();
    Vasu.setData();
    Employee ::countdisplay(); // this scope doesn't require any object

    Dev.getData();
    Dev.setData();
    Employee ::countdisplay();

    Aenansh.getData();
    Aenansh.setData();
    Employee ::countdisplay();

    /*without static variable, we need to initialize count with 0 then everytime we call a class function for each objects, the count
    will be initialized by 0 instead of the incrementation from previous object function call */
    return 0;
}