69e17a6a_otected_Mode_Memory_Management__Designated_Role
[Field] P [Designated Role] 
Segment Present Bit This bit specifies whether the segment is present in memory. When this bit is clear, a segment-not-present exception is generated whenever a selector for the descriptor is loaded into one of the segment registers. This is used to notify the operating system of any attempt to access a segment which has been swapped to disk (virtual memory support) or which was not previously allocated (a protection violation).
Protected-Mode Memory Management
Designated Role