>[!tldr] Page table entry >A *page table entry* is indexed by the [[Virtual page number (VPN)|virtual page number]] and contains the [[Physical Frame Number (PFN)|physical frame number]] which is how the mapping between the two is carried out. However, the entry also contains some other management fields such as: >- Present: If mapping is still valid or not. As the [[Memory frame|frame]] may have been reclaimed. >- Dirty: If the [[Memory frame|frame]] has been written too. For example if it represents something on disk we know it still need to be copied down to disk. >- Access: If the [[Memory frame|frame]] has been accessed by the [[Process|process]] for read or write operations. >- Protection: If the [[Process|process]] has read/write/execute permissions on the memory. > >Though these differ by architecture. See below for a particular example. >![[page_table_entry.png]]