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Handptright limit specifies the length of the segment

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handptright limit – specifies the length of the segment. square6 Segment-table base register (STBR) points to the segment table’s location in memory. square6 Segment-table length register (STLR) indicates number of segments used by a program; segment number s is legal if s < STLR.
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Silberschatz, Galvin and Gagne 2002 9.46 Operating System Concepts Segmentation Architecture (Cont.) square6 Relocation. handptright dynamic handptright by segment table square6 Sharing. handptright shared segments handptright same segment number square6 Allocation. handptright first fit/best fit handptright external fragmentation
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Silberschatz, Galvin and Gagne 2002 9.47 Operating System Concepts Segmentation Architecture (Cont.) square6 Protection. With each entry in segment table associate: handptright validation bit = 0 illegal segment handptright read/write/execute privileges square6 Protection bits associated with segments; code sharing occurs at segment level. square6 Since segments vary in length, memory allocation is a dynamic storage-allocation problem. square6 A segmentation example is shown in the following diagram
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Silberschatz, Galvin and Gagne 2002 9.48 Operating System Concepts Segmentation Hardware
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Silberschatz, Galvin and Gagne 2002 9.49 Operating System Concepts Example of Segmentation
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Silberschatz, Galvin and Gagne 2002 9.50 Operating System Concepts Sharing of Segments
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Silberschatz, Galvin and Gagne 2002 9.51 Operating System Concepts Segmentation with Paging – MULTICS square6 The MULTICS system solved problems of external fragmentation and lengthy search times by paging the segments. square6 Solution differs from pure segmentation in that the segment-table entry contains not the base address of the segment, but rather the base address of a page table for this segment.
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Silberschatz, Galvin and Gagne 2002 9.52 Operating System Concepts MULTICS Address Translation Scheme
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Silberschatz, Galvin and Gagne 2002 9.53 Operating System Concepts Segmentation with Paging – Intel 386 square6
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Silberschatz, Galvin and Gagne 2002
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