Static variable definition in Header file

TTCounter.c

#include "TTCounter.h"
#include "TTDislikeCounter.h"
#include "TTLikeCounter.h"

void printTotalCounter() {
  printf("total counter: %d", totalCounter);
}

int main(int argc, char *argv[]) {
  addDislikeToTotalCounter();
  addLikeToTotalCounter();
  printTotalCounter();
  return 0;
}

TTCounter.h

// TTCounter.h
static int totalCounter = 0; 

TTDislikeCounter.c

#include "TTCounter.h"

void addDislikeToTotalCounter() {
  totalCounter++;
}

TTDislikeCounter.h

// TTDislikeCounter.h

void addDislikeToTotalCounter();

TTLikeCounter.c

#include "TTCounter.h"

void addLikeToTotalCounter() {
  totalCounter++;
}

TTLikeCounter.h

// TTLikeCounter.h

void addLikeToTotalCounter();