Add words BIT@ and BIT!

blk/050

@@ -4,6 +4,8 @@ Memory
 !        n a --          Store n in address a
 ?        a --            Print value of addr a
 +!       n a --          Increase value of addr a by n
+BIT@     b a -- f        Get bit b from addr a.
+BIT!     f b a --        Set bit b to f in addr a.
 C@       a -- c          Set c to byte at address a
 C@+      a -- a+1 c      Fetch c from a and inc a.
 C@-      a -- a-1 c      Fetch c from a and dec a.
@@ -11,6 +13,4 @@ C!       c a --          Store byte c in address a
 C!+      c a -- a+1      Store byte c in a and inc a.
 C!-      c a -- a-1      Store byte c in a and dec a.
 CURRENT  -- a            Set a to wordref of last added entry.
-CURRENT* -- a            A pointer to active CURRENT*. Useful
-                         when we have multiple active dicts.
                                                         (cont.)

blk/051

@@ -1,3 +1,5 @@
+CURRENT* -- a            A pointer to active CURRENT*. Useful
+                         when we have multiple active dicts.
 FILL     a n b --        Fill n bytes at addr a with val b.
 HERE     -- a            Push HERE's address
 H@       -- a            HERE @

blk/404

@@ -4,9 +4,11 @@
     DUP NOT IF DROP 0x0c RAM+ @ THEN  ( 0c == C<* )
     EXECUTE
 ;
-
 : , HERE @ ! HERE @ 2+ HERE ! ;
-
 : C, HERE @ C! HERE @ 1+ HERE ! ;
-
+: BIT@ ( bit addr -- f ) C@ SWAP RSHIFT 0x01 AND ;
-
+: BIT! ( f bit addr -- )
+    SWAP 0x01 SWAP LSHIFT ROT ( addr mask f )
+    IF OVER C@ OR
+    ELSE 0xff XOR OVER C@ AND THEN ( addr flg )
+    SWAP C! ;