Given the following page table:
What are the physical addresses corresponding to the following logical addresses?
Logical address
0 4096
430 4526
2071 6167
4129 5123
5209 memory protection error
6.14 Why do virtual memory systems include a ???modified??? bit in the page table entry?
If a process has written to a page, it will take more time to reallocate that memory to a new page.
If a page has been modified, the system must write the page to disk before the frame of memory
can be used for another page mapping. On the other hand, the system does not need to write and
ANSWERS TO REVIEW QUESTIONS 203
Page Frame
0 4
1 10
2 6
3 7
4 5
unmodified page to disk before remapping the frame for other use, because an unmodified page is
always available in its original form on the disk already. Often page replacement algorithms take
this difference into account in order to speed execution. Other things being equal, the system will
remap an unmodified page before it will remap a page that has been modified.
6.15 Why would fixed-length record files be a good choice for storing data from database tables?
With fixed-length record files, the system can easily calculate the exact address within the file of any
record in the file.
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