how to use Exceptions in C++ program? -

hey , trying inherit exception class , make new class called nonexistingexception: wrote following code in h file:

class nonexistingexception : public exception { public:     virtual const char* what() const throw()  {return "exception: not find       item";} }; 

in code before sending function writing

try{     func(); // func function inside class } catch(nonexistingexception& e) {     cout<<e.what()<<endl; } catch (exception& e) {      cout<<e.what()<<endl; } 

inside func throwing exception nothing catches it. in advance help.

i this:

// derive std::runtime_error rather std::exception // runtime_error's constructor can take string parameter // standard's compliant version of std::exception can not // (though compiler provide non standard constructor). // class nonexistingvehicleexception : public std::runtime_error {     public:        nonexistingvehicleexception()          :std::runtime_error("exception: not find item") {} };  int main() {     try     {         throw nonexistingvehicleexception();     }     // prefer catch const reference.     catch(nonexistingvehicleexception const& e)     {         std::cout << "nonexistingvehicleexception: " << e.what() << std::endl;     }     // try , catch exceptions     catch(std::exception const& e)     {         std::cout << "std::exception: " << e.what() << std::endl;     }     // if miss ... catch left over.     catch(...)     {         std::cout << "unknown exception: " << std::endl;         // re-throw one.         // not handled want make sure handled correctly         // os. allow exception keep propagating.         throw;          // note: re-throw exceptions main         //       did not explicitly handle , correct.     } }