diff --git a/lib/ldpcsim.f90 b/lib/ldpcsim.f90
index 20ecc7834..607a1de96 100644
--- a/lib/ldpcsim.f90
+++ b/lib/ldpcsim.f90
@@ -1,13 +1,12 @@
 program ldpcsim
 
+! simulate with packed 72-bit messages and 8-bit hash - so only makes
+! sense to use this with codes having K=80.
+
 use, intrinsic :: iso_c_binding
 use hashing
 use packjt
 
-! To change to a new code, edit the following line and the filenames
-! that contain the parity check and generator matrices.
-! parameter (N=128, K=80) ! M and N are global variables on the C side.
-
 character*22 msg,msgsent
 integer*4 i4Msg6BitWords(12)
 integer*1, target:: i1Msg8BitBytes(10) ! 72 bit msg + 8 bit hash