diff --git a/content/notes/02-combinatorial-logic.md b/content/notes/02-combinatorial-logic.md
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 - [slides](https://blackboard.otago.ac.nz/bbcswebdav/pid-2954102-dt-content-rid-18888626_1/courses/COSC204_S2DNI_2022/L2%20-%20Combinatorial%20Logic.pdf)
 
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 # Circuit basics:
 - current flows + to -
 - input to a unit (e.g., LED) is the + end
diff --git a/content/notes/boolean-equations.md b/content/notes/boolean-equations.md
index e427f398e..ea49d019e 100644
--- a/content/notes/boolean-equations.md
+++ b/content/notes/boolean-equations.md
@@ -5,4 +5,31 @@ tags:
 - cosc204
 ---
 
-Often used to describe 
+Often used to describe/define Combinatorial logic circuits
+
+# Precedence
+Precedence
+- NOT is unary, so it has the highest precedence
+- AND is mulitply, so it comes next
+- OR is like plusl, to it comes last
+
+![Precedence table|200](https://i.imgur.com/jPlrVwW.png)
+
+# Creating boolean equations
+
+![example equation](https://i.imgur.com/fiNKbJT.png)
+![equivalent truth table](https://i.imgur.com/wlm0Cu1.png)
+
+Creating boolean equations:
+- for each row where output is 1
+- write the equation as a function of the inputs  (using AND)
+- Write the final equation, putting OR between each clause
+
+# De Morgan's Theorum
+- !(A + B) = A! & !B
+- !(A + B + C + ... + X) = !A & !B & !C & ... & !X
+- [truth table](https://i.imgur.com/QegVxkx.png)
+- any boolean function can be represented as the sum of logical products
+- All combinatorial circuits can be described using just one gate type (either nand or nor) [^2]
+
+[^2] : The Apollo Guidance Computer used about 5600 NOR gates and no other gate types!
\ No newline at end of file
diff --git a/content/notes/combinatorial-logic-circuit.md b/content/notes/combinatorial-logic-circuit.md
new file mode 100644
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+---
+title: "combinatorial-logic-circuit"
+aliases: logic circuit
+tags: 
+- cosc204
+---
+
+
diff --git a/content/notes/cosc-204.md b/content/notes/cosc-204.md
index e6067d690..97a99c720 100644
--- a/content/notes/cosc-204.md
+++ b/content/notes/cosc-204.md
@@ -17,6 +17,8 @@ tags:
 - [unicode](notes/unicode.md)
 - [digital-data](notes/digital-data.md)
 - [memory](notes/memory.md)
+- [boolean-equations](notes/boolean-equations.md)
+- 
 
 - Hardware
 - Assembly