CursorBack(screen, n) register TScreen	*screen; int		n;
CursorBack(register TScreen *screen, int n)
CursorBack(screen, n)register TScreen	*screen;int		n;{	register int i, j, k, rev;	if((rev = (term->flags & (REVERSEWRAP | WRAPAROUND)) ==	                         (REVERSEWRAP | WRAPAROUND)) != 0	 && screen->do_wrap)		n--;	if ((screen->cur_col -= n) < 0) {		if(rev) {			if((i = (j = screen->max_col + 1) * screen->cur_row +			 screen->cur_col) < 0) {				k = j * (screen->max_row + 1);				i += ((-i) / k + 1) * k;			}			screen->cur_row = i / j;			screen->cur_col = i % j;		} else			screen->cur_col = 0;	}	screen->do_wrap = 0;	_CheckSelection(screen);}