Name: ______________________________________

1. What two kinds of systems do not use virtual memory?

   ______________________ _______________________

2. Why don't they use virtual memory?

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3. We load a program two different times. We are using a debugger which shows us that the program loaded at different addresses in memory each time. What is this called?

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4. In the example in the text in section 17.3.1, assume that at a point in time the status is:

   Page	Dirty Bit	Accessed Bit
   1(*)	0	1
   2	1	1
   3	1	1
   4	0	0
   5	0	1
   6	1	1
   7	0	0
   8	1	1
   9	1	1
   10	1	1
   11	1	1
   12	0	1
   13	1	1
   14	1	1
   15	1	1
   16	0	0

   
   (*) Page 1 is virtual = real and cannot be used for other programs.
   If we load a Program 4 which actively uses 5 pages, which 5 pages are most likely to be selected?

   ___ ___ ___ ___ ___ ___

   Which pages would be written to the swap file? ___ ___ ___ ___ ___

5. Write the PMT for Program 4 at this point. Use the format of the other PMTs in section 15.3.1.

   Virtual Page	Real Page
   ______	______
   ______	______
   ______	______
   ______	______
   ______	______
   ______	______
   ______	______
   ______	______
   ______	______
   ______	______
   ______	______

6. Which measurement in this list would indicate possible thrashing?
   1. ___ 4 page faults per minute.
   2. ___ 20 reads from the swap file per minute.
   3. ___ 5 writes to the swap file per minute.
   4. ___ Average of 1 free page.
   5. ___ 20 page faults per second.
   6. ___ Machine has 256 Meg. The swap file has 350 Meg used.

   Explain your answer:

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7. If a program cycles through a large array, reading all the values to perform a mathematical calculation, which bit(s) will be turned on for all the pages? ___________ _________

8. If a program cycles through a large array, changing every other element as part of a mathematical calculation, which bit(s) will be turned on for all the pages? ___________ ____________

9. If a program has code of 30 Meg and data areas of 80 Meg, but a working set of only 10 Meg, where is all the extra code and data stored?

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10. Explain what happens if you write a rogue program which attempts to overwrite the interrupt table in low memory in order to gain control of the system.

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