static Member

static members are only declared in class declaration, not defined. They must be explicitly defined outside the class using scope resolution operator.

#include using namespace std;   class A {     int x; public:     A() { cout << "A's constructor called " << endl;  } };   class B {     static A a; public:     B() { cout << "B's constructor called " << endl; }     static A getA() { return a; } };   A B::a;  // definition of a   int main() {     // static member 'a' is accessed without any object of B     A a = B::getA();       return 0; }

Output:

A's constructor called