c++ - No error for not initializing reference variable of class -

i newbie , have basic doubt relationship between object creation , constructors.

program- 1

 #include<iostream>  using namespace std;  class xxx{      private: int x;      public: xxx(){cout<<"constructer called"<<endl;}  };  int main(int argc, char *argv[])  {      xxx x1;        //constructor called      return 0;  } 

output- constructor called

program- 2

 #include<iostream>  using namespace std;  class xxx{      private: int x;      public: xxx(){cout<<"constructer called"<<endl;}  };  int main(int argc, char *argv[])  {      xxx x1();        //constructor xxx() not called.      return 0;  } 

output- blank information helpfule

 xxx x1; 

creates object of class xxx, therefore, calls default constructor of class xxx.

xxx x1(); 

declares function returns object of class xxx , function name x1, takes no parameter. not instantiation of class xxx, therefore, there no constructor being called.