Add assembly language reference

readme.md

@@ -56,3 +56,25 @@ Misc:
 ### Maybe someday
 
 - timer (for a version in software/electronic-hardware)
+
+## Assembly language
+
+
+    ADD $01         ; comments follow a `;`
+
+    ADD $FF         ; this is direct addressing
+    ADD ($CC)       ; this is indirect addressing
+
+    END             ; END, CFC, and CHP don't require arguments
+                    ; (a default value of 0 will be used as their operand)
+
+    @subroutine     ; create a label
+        ADD $01     ; (it must be on the line before the code it names)
+        ADD $02
+
+    JMP @subroutine ; use a label as an argument
+                    ; the label will be replaced with
+                    ; the address of the label
+
+- Hexadecimal numbers are preceded by a `$`
+- Whitespace is ignored