some complement in 11.27

notes/12.md

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+# Memory
+
+## Memory Hierachies
+
+Storage media typically trades off speed with capacity
+
+
+## Locality
+
+* **Temporal Locality**: recently referenced items are likely to be referenced again soon
+* **Spaitial Locality**: items with nearby addresses are tend to be referenced close together in time
+
+## Cache Concepts
+