extern  void abort_program(int abort_code);
extern  void draw_box(int xmin,int xmax,int ymin,int ymax);
extern  void draw_tbox(int col1,int col2,int row1,int row2);
extern  int exists(char *filename);
extern  void flushkey(void );
extern  void initialize(void );
extern  void init_mouse(void );
extern  int printer_ready(void );
extern  int scale(int y);
extern  int select_mode(void );
extern  void terminate(void );
extern  void wait_for_keystroke(void );
extern  void wait_for_mouse_buttons(void );