diff --git a/lang/HDL.wiki b/lang/HDL.wiki
index b0d59a4..8de4f0e 100644
--- a/lang/HDL.wiki
+++ b/lang/HDL.wiki
@@ -3,4 +3,13 @@
 HDL or Hardware Description Language is a language for 'programing' logic gates
 for digital electronics.
 
+== Modeling ==
 
+There are various ways to describe the function of the digital circut in
+question.
+
+=== Gate Level Modeling ===
+
+* Use representations of gates (and, nand, or, etc)
+* Syntax of `not(OUTPUT, INPUT)`
+* Wires often used as a intermediate for signals between gates