#include<iostream>

class class_test
{
   public:
      static int a;

};

int class_test::a; // Declare before use
int main()
{
   using namespace std;
 //   int class_test::a; Cannot declare here
   class_test::a=20;
   printf("\n class_test::a :: %d ", class_test::a );
  
   return 0;
}



OUTPUT
========================================

class_test::a :: 20