CSCI 3000
Spring 2017
Practice Questions for Exam 2

1. True/false

   1. Virtual memory makes overlays almost entirely unnecessary. Answer.

   2. Virtual memory can realistically be implemented entirely in software, without any special hardware support. Answer.

   3. A page table is used to translate logical addresses to physical addresses. Answer.

   4. The main advantage of a two-level page table over a single-level page table is that the two-level table is faster to search. Answer.

2. [MC] A translation lookaside buffer is a mechanism for

   1. speeding up processing of page faults.

   2. speeding up lookups in the page table.

   3. reducing the size of the page table.

   4. reducing the frequency of page faults.

   Answer.

3. [MC] The main difference between swapping and virtual memory is that

   1. virtual memory allows only part of a process to be in memory, but swapping insists that a process is either entirely in or entirely out of memory.

   2. swapping allows only part of a process to be in memory, but virtual memory insists that a process is either entirely in or entirely out of memory.

   3. virtual memory and swapping have nothing in common. They are trying to solve unrelated problems.

   4. there is no difference. Swapping is just another name for virtual memory.

   Answer.

4. [MC] Memory compactification is a solution to

   1. the dynamic linking problem.

   2. the static linking problem.

   3. the internal fragmentation problem.

   4. the external fragmentation problem.

   Answer.

5. [MC] What is thrashing?

   1. A computer is thrashing when it is running only I/O-bound processes.

   2. A computer is thrashing when it is running only compute-bound processes.

   3. A computer is thrashing when it is performing a high number of page faults per second.

   4. A computer is thrashing when it is used to harvest wheat.

   Answer.

6. [MC] When a system detects that it is thrashing, one thing that it can do to improve performance is

   1. reduce the amount of multiprogramming.

   2. increase the amount of multiprogramming.

   3. decrease the duration of a time slice.

   4. increase the duration of a time slice.

   Answer.

7. [MC] An important difference between a hard link and a symbolic link in a file system is

   1. Reference counts are kept for hard links but not for symbolic links.

   2. Reference counts are kept for symbolic links but not for hard links.

   3. Hard links are allowed to create cycles, but symbolic links are not.

   4. Symbolic links require much less disk space than hard links.

   Answer.

8. [MC] An advantage of a file allocation table (FAT) file structure over a simple linked file structure is

   1. The file allocation table uses much less disk space than the linked structure.

   2. The simple linked structure uses much less disk space than the file allocation table method.

   3. The file allocation table method allows faster seeks in files.

   4. The simple linked allocation method allows faster seeks in files.

   Answer.

9. [MC] A Unix inode stores

   1. Only the name of a file.

   2. Only file allocation information about a file.

   3. Only access permission information about a file.

   4. Access permissions and file allocation information for a file, as well as some other information.

   Answer.

10. [MC] Contiguous allocation of files has some advantages and some disadvantages. Which of the following is NOT a disadvantage of contiguous allocation?

    1. Fragmentation of the disk free blocks.

    2. Slow seek time.

    3. Difficulty of adding new blocks to the end of a file.

    4. Difficulty of adding new blocks to the beginning of a file.

    Answer.

11. [MC] Clustering is

    1. Creating large logical disk blocks from collections of contiguous physical disk blocks.

    2. Allocating directories close to one another.

    3. Allocating files close to one another.

    4. Moving the blocks of a file closer to one another on the disk.

    Answer.

12. [MC] An advantage of clustering for a file allocation table is

    1. The file allocation table can be made contiguous on the disk.

    2. The file allocation table is smaller.

    3. The file allocation table can probably fit in a single disk block.

    4. The file allocation table becomes entirely unnecessary.

    Answer.

13. [MC] To read or write a block on a disk, a process must

    1. acquire the disk resource for its private use.

    2. send a direct i/o request to the disk.

    3. first check that the disk is powered up and spinning.

    4. make a system call.

    Answer.

14. [MC] A directory is a kind of file. Which of the following is NOT a reason for not providing a means for processes to directly read and write directories the way ordinary files are read and written?

    1. Directory organization changes from one operating system to another, so programs that do direct access to directories are non-portable.

    2. Allowing a process to write a directory will allow the process to replace any permission information that is stored in the directory, and hence will reduce system security.

    3. Processes that write a directory might destroy the directory structure, causing a large part of the file system to be lost.

    4. A process is normally not allowed to find out the names of the files that are part of a directory.

    Answer.