diff --git a/notes.adoc b/notes.adoc
index 5e33b5a..a4eabf4 100644
--- a/notes.adoc
+++ b/notes.adoc
@@ -129,6 +129,9 @@ ways:
 
 * Much of the code still uses FORTRAN-style uppercase names.
 
+* The code still assumes one-origin array indexing.  Thus, arrays are
+  a cell larger than they strictly need to be and cell 0 is unused.
+
 * The code is still mostly typeless, slinging around machine longs
   like a FORTRAN or BCPL program.  Some (incomplete) effort has been made
   to introduce semantic types.