c++ - How to call a function from a separate cpp file in the main.cpp file? -

i have following timer.cpp, timer.h, , main.cpp files. trying call functions timer.cpp file in main.cpp file , have included timer.h in main, still not working. can please explain why? little rusty c++ , feel making silly mistake. in advance help.

#timer.h file  #ifndef __notes__timer__ #define __notes__timer__  #include <iostream>  class timer { public:     timer();     void start();     void stop();     void clear();     float getdelta(); };  #endif 

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#timer.cpp file     #include "timer.h"   clock_t starttime; clock_t stoptime;  timer::timer(){     starttime = 0;     stoptime = 0; }//timer  void start(){     starttime = clock(); }//start  void stop(){     stoptime = clock(); }//stop  float getdelta(){     return stoptime-starttime; }//getdelta 

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#main.cpp file  #include "timer.h" #include <iostream>  using namespace std;   int main(){     char quit;     start();     cout << "would quit? y or n: ";     cin >> quit;     if (quit != 'y' || quit != 'y'){         while (quit != 'y' || quit != 'y'){             cout << "would quit? y or n: ";             cin >> quit;         }//while     }//if     else {         stop();         cout << getdelta();         exit(0);     }//else }//main 

you can use these functions in timer.c , use class::function