can someone say what''s wrong with my code.. when i compile it i get linker error message "main.obj : error LNK2001: unresolved external symbol "class TEST test" (?test@@3VTEST@@A)". -------main.cpp #include #include "test.h" int main(int argvc, char* argv[]) { printf("%i", test.t()); return 0; } -------test.h #ifndef TEST_H #define TEST_H class TEST { public: int t(); }; extern TEST test; // this causes an error.. why? #endif TEST_H -------test.cpp #include "test.h" int TEST::t() { return 54; // amazing function? =) } ok... so what should i do different? and as you can see, i''m new at c++.. =)

the problem is that you only declare "test" by using the extern keyword.
if you use extern, you must define the variable somewhere else.
either you put "TEST test;" in front of your main.cpp file to define test as a global variable, or you just ditch your extern keyword.
then the linker shouldn''t complain any more

ridcully