example.c

#include <stdio.h>

int i = 0; // Static values are initialized to 0 according to C spec, this just makes it explicit

int foo(){
  i = i + 1;
  return i;
}

int main(){
  int x;
  for(x = 0; x < 10; x++){
    int z = foo();
    printf("I have called foo %d times\n", z);
  }
  return 0;
}