/* file: helloworld_with_preproc.c
   K&R "hello world!" modified
*/

// conditional compilation; note C++-style comment
#ifdef HEADERS
#include <stdio.h>
#else
#warning "declare printf explicitly" // tracing precompiler code
extern int printf(const char*,...);
#endif

int main(void)
{
  printf("Hello world!\n");

  return 0;

}/* end main */