c++ - How to properly include Header and Implementation Files? -

i novice programmer in c++, , getting compiling error

undefined symbols architecture x86_64 

supposedly originates how header files , implementation files included/coded.

below code generates compiling error receiving

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main

//main.cpp #include <iostream> #include <string> #include "animal.hpp"  using namespace std;  int main(){     animal mypet;     mypet.shout();      return 0; } 

header

//animal.hpp #ifndef h_animal #define h_animal  using namespace std;  #include <string>  class animal{ public:     animal();      void shout(); private:     string roar; }; #endif 

implementation

//animal.cpp #include "animal.hpp" #include <string>  animal::animal(){     roar = "..."; }  void animal::shout(){     roar = "roar";     cout << roar; } 

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this code generates compiling issue. how issue resolved?

thanks time

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edit

undefined symbols architecture x86_64:   "animal::shout()", referenced from:       _main in test-5f7f84.o   "animal::animal()", referenced from:       _main in test-5f7f84.o ld: symbol(s) not found architecture x86_64 clang: error: linker command failed exit code 1 (use -v see invocation) 

maybe might want see alternative set of 3 files, things little more "sorted", know, things put @ places "really" belong to.

so here's "new" header file ..

//animal.hpp #ifndef h_animal #define h_animal  #include <string> // suffices  // interface. class animal {     std::string roar; // private  public:     animal();     void shout(); };  #endif 

then source file ..

//animal.cpp #include "animal.hpp"  #include <iostream> // suffices  // constructor. animal::animal()     :     roar("...") // data member initializer {}  // member function. void animal::shout() {     roar = "roar";     std::cout << roar; } 

and main program ..

//main.cpp #include "animal.hpp"  int main(){     animal thepet;     thepet.shout(); // outputs: `roar' } 

plus little gnu makefile ..

all: default run  default: animal.cpp main.cpp     g++ -o main.exe animal.cpp main.cpp  run:     ./main.exe  clean:     $(rm) *.o *.exe 

kick-off things typing "make" in cmd-line. did it? -- regards, m.