An Operating Systems Vade Mecum

80 Space Management Chapter 3virtual addresssegmentoffsetstartpermis-sionssizestartphysical addressaddress-translation tableFigure 3.11 Hardware translation for segmentationVirtual address Access type Physical address0 R 13426 217 W 1017 217 R trap: security violation 232 R trap: offset out of range 394 R trap: missing segment, security violation 499 X 10099725 X trap: invalid segment number Several traps can apply to the same reference. For example, the Read reference to location394 traps both because the segment is missing and because of security violation. Ifthe machine can only report one trap for a reference, it is better to report traps that indicateprogram error (like security violation) than those that indicate that help from thestorage manager is needed (like missing segment).