n In each segment table entry we have both the starting address and length of the segment u the segment can thus dynamically grow or shrink as needed u address validity easily checked with the length field n But variable length segments introduce external fragmentation and are more difficult to swap in and out... n It is natural to provide protection and sharing at the segment level since segments are visible to the programmer (pages are not) n Useful protection bits in segment table entry: u read-only/read-write bit u Supervisor/User bit