SEGMENTATION-PROTECTION AND SHARING

• Protection Bit-Read Only or Execute Only
• The memory mapping hardware will check the protection bits associated with each segment table entry to prevent illegal accesses to memory,such as attempts to write into read-only segment,or to use an execute-only segment as data.
• Segmentation involves sharing of code or data.
• Each process has a segment table associated with it,the dispatcher uses to define the hardware segment table when this process is given the CPU.
• Segments are shared when entries in the segment tables of two different processes point to the same physical location.
• Sharing occurs at the segment level.
• Since segments vary in length, memory allocation is a dynamic storage-allocation problem.