Page table entry
A page table entry is indexed by the virtual page number and contains the 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 frame may have been reclaimed.
- Dirty: If the 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 frame has been accessed by the process for read or write operations.
- Protection: If the process has read/write/execute permissions on the memory.
Though these differ by architecture. See below for a particular example.
