anchor.diff:  : fb8-install ( width height #columns #lines -- )
   	1 to screen-depth
   	2swap  to screen-height  to screen-width
  +	screen-width to screen-line-bytes
   	screen-#rows min to #lines
   	screen-#columns min to #columns
   	screen-height char-height #lines * - 2/ to window-top
  
positive.code: : fb8-background inverse? ;
  : fb8-foreground inverse? invert ;
  
  : fb8-lines2bytes ( #lines -- #bytes ) char-height * screen-width * screen-depth * ;
  : fb8-columns2bytes ( #columns -- #bytes ) char-width * screen-depth * ;
  : fb8-line2addr ( line# -- addr )
  	char-height * window-top + screen-width * screen-depth *
  	frame-buffer-adr + window-left screen-depth * +
  ;
  
  
negative.code: 0 VALUE screen-height
  0 VALUE screen-width
  0 VALUE screen-depth
  0 VALUE screen-line-bytes
  0 VALUE window-top
  0 VALUE window-left
  
  