diff --git a/noid.py b/noid.py
index 893887d..df4433e 100644
--- a/noid.py
+++ b/noid.py
@@ -170,6 +170,18 @@ class Minter(Persistent):
         return s
 
     def _checkchar(self, id):
+        # 1. Return undef if id is not set
+        # 2. init lastchar to last char of the id, and remove that char from id
+        # 3. init pos to 1
+        # 4. init sum to 0
+        # 5. declare c
+        # 6. for each character of the id
+        #    - get the ordinal value of the character
+        #    - increment sum with the pos * the index value of the char in legalstring
+        #    - increment pos
+        # 7. init checkchar to the value of xdig[sum % alphacount]
+        # 8. return the concat of id and checkchar is lastchar equal to '+' or checkchar
+        # 9. return None
         pass