diff --git a/Operating Systems/Virtual Memory.md b/Operating Systems/Virtual Memory.md
index 4aef9ef..3c0a0d0 100644
--- a/Operating Systems/Virtual Memory.md	
+++ b/Operating Systems/Virtual Memory.md	
@@ -88,7 +88,13 @@ Give the process(es) more memory by:
 - Taking it from another process
 - Swap out shit until demand is lower (scheduler)
 
-## Prepaging
+
+## Inverted page table
+Inverted page tables are a memory management method that uses a single table for the entire system to map physical memory addresses to virtual addresses. Instead of each process having its own page table, the inverted page table has entries for each physical page.
+
+
+## I/O Interlock
+Pages must sometimes be locked into memory (i.e. I/O). This is what this is called.