#define SYSFUNC               0xD5
  #define REBOOT                0xAB
  #define REBOOTDEV             "\\DEV\\DOS$

  HFILE  hREBOOT;
  ULONG  ulAction;

  rc = DosOpen(REBOOTDEV,
               &hREBOOT,
               &ulAction,
               0L,
               FILE_NORMAL,
               FILE_OPEN,
               OPEN_SHARE_DENYNONE | OPEN_ACCESS_READWRITE,
               0L);
  if (rc == 0)
  {
     DosDevIOCtl(hREBOOT,
                 SYSFUNC,
                 REBOOT,
                 NULL,
                 0L,
                 NULL,
                 NULL,
                 0L,
                 NULL);
     DosClose(hDD);
  }

Make sure that the functions DosOpen and DosDevIOCtl are prototyped.