anchor.diff:  \ pg 23 words
   
   t: 1+		1 + ;
  -t: 1-		-1 + ;
   t: CELL-	-8 + ;
   t: CELL+	8 + ;
   t: CELLS	8 * ;
  
positive.code: 
  \ pg 20
  
  t: =		XOR IF 0 EXIT THEN -1 ;
  t: U<		2DUP XOR 0< IF NIP 0< EXIT THEN - 0< ;
  t: <		2DUP XOR 0< IF DROP 0< EXIT THEN - 0< ;
  
negative.code: t: PACK$
    ALIGNED DUP >R OVER DUP 0 8 UM/MOD DROP - OVER + 0 SWAP !
    2DUP C! 1+ SWAP CMOVE R> ;
  
  \ Miscellaneous must-haves.
  
  t: 2*		1 LSHIFT ;
  t: 1-		-1 + ;
  
  \ I/O device drivers.
  S" v-mgia.fs" included	( MGIA video )
  