Implement CONSTANT, VARIABLE, VALUE and TO

prelude.f

@@ -177,6 +177,39 @@ CHAR . EMIT
 
 CHAR . EMIT
 
+\ Constants, variables and values
+
+: CONSTANT
+  WORD CREATE
+  DOCOL ,
+  LIT LIT ,
+  ,
+  LIT EXIT ,
+;
+
+: VARIABLE
+  WORD CREATE
+  DOVAR ,
+  0 ,
+;
+
+: VALUE
+  WORD CREATE
+  DOVAL , ,
+;
+
+: TO
+  ' 4+
+  STATE @ IF
+	LIT LIT , ,
+	LIT ! ,
+  ELSE
+	!
+  THEN
+; IMMEDIATE
+
+CHAR . EMIT
+
 \ Version number
 
 : VERSION-MAJOR 0 ;