CA170 - Introduction to Operating Systems

Answer all multiple-choice questions. 1 mark each. There is no negative marking.

1. Which of the following is an unusual permission field for a UNIX file:

   ----r-xr-x
   -rwx---r-x
   -rwxr-x---
   -rwxr-xr-x
   -rwx------
   

   
   

2. When a program is started:

   A copy of it is made in a volatile medium.
   Its data is copied into the registers.
   No copy of it is made, since a copy already exists.
   A copy of it is made in a non-volatile medium.
   It is pre-loaded into memory.
   

   
   

3. This program:

   // define a function:
   function f() { f(); } // function calls itself
   // start the program:
   f();

   Blocks all other processes from running.
   Is detected by the Operating System and terminated.
   Runs forever, time-sliced.
   Runs time-sliced until it crashes by running out of stack space.
   Runs time-sliced until it crashes with a bad memory access.
   

   
   

4. Linux dominates supercomputers and other specialist computer niches because:

   Windows Server dominates the server market.
   Microsoft does not write for supercomputers.
   Microsoft does not write for servers.
   Windows can be customised to unusual hardware.
   Linux does not dominate that market.
   Unix/Linux pulled ahead in the server market first.
   Open source Linux can be customised to unusual hardware.
   

   
   

5. One of the following file protections will break your web page:

   -------r-x
   -rwx---r-x
   -rwxr-xr-x
   -rwx---r--
   -rwxr-x--x
   -------r--
   -rwxr-xr--
   

   
   

6. What is wrong with this command?
   wget -O - https://biscuits.com/biscuit.jpg

   The URL may require https.
   The URL may require www.
   wget may not be installed.
   The JPEG should be saved into a file.
   The URL may not exist.
   There is nothing wrong with this command.
   

   
   

7. What command will search all your files for lines containing start of line, then any number of spaces, then the string "born"?

   grep "^born" *
   grep "^ born" *
   grep "^ .born" *
   grep "^ .*born" *
   grep "^.born" *
   grep "born" *
   grep "^ *born" *
   

   
   

8. If a program is not in the directories listed in the "PATH" environment variable:

   The directory needs to be put into the PATH.
   It needs to be executable to be run.
   It can be run by typing its absolute file path.
   It is a system error.
   It can run as normal.
   It cannot be run.
   The OS is broken.
   

   
   

9. On Linux, when you type a normal command, it should be in the PATH to run. Yet when you run ps -f you see a program running that is not in the PATH. How can this happen?

   There must be a system error.
   ps -f will not show this.
   This cannot happen.
   This always happens.
   The PATH must be wrong.
   You can run programs that are not in the PATH.
   

   
   

10. Compile-time binding works only on a:

    Multiple user, single process system.
    Multiple user, multiple process system.
    Single user, multiple process system.
    Single user, single process system.
    

    
    

11. As a result of the "unused RAM is wasted RAM" idea, we may:

    Keep data from terminated processes in memory. And pre-load processes that may be run later.
    Pre-load processes that may be run later.
    Allocate more memory than processes need.
    Run OS processes until memory is full.
    Run more processes until memory is full.
    Keep data from terminated processes in memory.
    

    
    

12. In my Shakespeare directory, you want to count on how many lines the string "King" appears in Shakespeare. Which of the following will answer that question?

    grep -i King */act* | wc -l
    grep -c King */act* | wc -l
    grep -ic King */act* | wc -l
    grep -ic King */act*
    grep -c King */act*
    grep -i King */act*
    grep King */act*
    grep King */act* | wc -l
    

    
    

13. What will this Shell script do?

    for i in *
    do
    rm i
    done

    It is a syntax error.
    Remove a file called i, perhaps multiple times.
    Remove all the files in the current directory.
    Remove all the files given in the arguments to the program.
    Remove all hidden files in the current directory.
    Remove all the files in the current directory, except for hidden files.
    

    
    

14. One of these is true.

    All users need the command-line.
    GUIs came before command-lines.
    Android's Unix-like command-line was key to its success.
    A command-line system is easier to automate than a GUI system.
    Unix systems rarely have a GUI.
    A command-line system is easier to use than a GUI system.
    Apple's Unix-like command-line was key to its success.
    

    
    

15. This command:
    sed -e 's|<|\&lt;|g'

    is displaying the start of HTML tags but not getting them interpreted.
    is redirecting output to a file.
    is a syntax error.
    is blanking out the start of HTML tags.
    is removing HTML tags.
    

    
    

16. If we have to remove a page from memory, what do we do?

    Discard it completely, since it is no longer needed.
    This never happens.
    Discard it completely, since it exists already on disk.
    Sometimes write it to disk, sometimes discard it completely.
    Terminate and restart the process.
    Write it to disk.
    

    
    

17. A user tries to start a program on a single-user, multiple-process system. Why is it not practical for the OS to say to the user: "I'm sorry, another program is occupying memory space 7000-8000. Please terminate the other program before running your program"

    The source code may not be available.
    It may not be possible to terminate the other program.
    The user will not understand this message.
    Our program should not ask for memory space 7000-8000.
    

    
    

18. I am in the directory   /stuff/and/things   and I type:   cd ../../../more/things   - What directory am I in now?

    /stuff/and/more/things
    /stuff/more/things
    /more/things
    /stuff/and/things/more/things
    The command is an error.
    

    
    

19. The commands "cd" followed by "cd public_html" followed by "mkdir ../stuff" make a directory called:

    $HOME/public_html/stuff
    $HOME/../stuff
    It does not make a directory.
    $HOME/stuff
    /stuff
    /public_html/stuff
    

    
    

20. What is this script doing?

    grep string file > /dev/null
    if test "$?" = "0"
    then
    ...

    Listing the lines of the file in which the string occurs.
    Testing whether or not the string occurs in the file, without listing the lines on which it does.
    Listing the lines of the file in which the string occurs, then querying the number of arguments to the program.
    Building an output file of the lines on which the string occurs, and then proceeding with a test of whether there were any such lines.
    

    
    

21. Only one of the following makes any kind of sense as a possible permission field for a UNIX file. Which one?

    --w-------
    ----rwxrwx
    --rwx-----
    -r--------
    ----r-----
    

    
    

22. Typing the command man man > man does what?

    Permissions error.
    "man" should only appear once.
    Syntax error.
    "man" should only appear twice.
    Correct syntax, but bad argument to "man".
    Stores the manual page for "man" in a file with a terrible filename.
    

    
    

23. What will this shell script do?

    ls$1

    List the files given in the argument.
    List the files given in the arguments.
    List all files.
    Probably fail unless arguments are blank.
    Will always fail.
    

    
    

24. On a multi-user system, when one user's program divides by zero:

    It keeps running, but no other user's program can run.
    The program has to be re-loaded.
    An interrupt is generated and the program is terminated.
    It keeps running, interleaved with other users' programs.
    

    
    

25. We are searching for text in chapters of a book, called names like chap17.html. One of these is definitely not right:

    grep Scotland ../chap*html
    grep Scotland chap*html
    grep Scotland \*chap*html
    grep Scotland /*chap*html
    grep Scotland */*/chap*html
    grep Scotland *chap*html
    grep Scotland ./chap*html
    grep Scotland */chap*html