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CA170 (CSC1011) - Introduction to Operating Systems

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Student number
Linux userid (e.g. jim.smith2)
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Multiple choice

Answer all multiple-choice questions. Identical marks each. There is no negative marking.

Which of the following is an unusual permission field for a UNIX file:
-rwxr-x---
-rwx------
-rwxr-xr-x
-rwx---r-x
----r-xr-x
One of the following file protections will break your web page:
-rwx---r-x
-rwxr-x--x
-------r--
-rwx---r--
-------r-x
-rwxr-xr-x
-rwxr-xr--
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?
You can run programs that are not in the PATH.
There must be a system error.
The PATH must be wrong.
This cannot happen.
This always happens.
ps -f will not show this.
The user's program has started. The OS needs to change what memory locations things map to, but binding is done at load-time. Why is it not practical for the OS to say to the user: "Please reload your program so I can re-do the binding":
This means that some programs simply cannot run.
The user will not understand this message.
Reloading will take a lot of time.
The source code may not be available.
When you type a program with a file wildcard as argument like: prog *html the Linux shell expands the wildcard and passes the result to the program. Why does it not just pass "*html" to the program?
It does pass "*html" to the program.
Wildcard matching is not needed if there is only one file.
The program does not have permission to do wildcard matching.
The program might not want to do wildcard matching.
Every program would have to re-implement its own wildcard matching.
This is a lack of functionality in some Shells. It is fixed in others.
You write a simple program in the interpreted UNIX scripting language Shell. You then want to run the program on a different type of machine (different chip, but still running UNIX). Which is normally true:
The program must be re-assembled.
The program must be re-compiled.
The program must be re-written.
It should run without change.
When we run multiple programs at the same time, we need:
Multiple terminals.
Multiple CPUs.
Memory protection.
We cannot do this.
File protection.
What will this Shell script do?
for i in $*
do
rm i
done

Remove all the files in the current directory.
Remove a file called i, perhaps multiple times.
It is a syntax error.
Remove all the files in the current directory, except for hidden files.
Remove all hidden files in the current directory.
Remove all the files given in the arguments to the program.
On a multi-user system, when one user's program divides by zero:
The program has to be re-loaded.
It keeps running, interleaved with other users' programs.
It keeps running, but no other user's program can run.
An interrupt is generated and the program is terminated.
Swapping a process or part of a process to disk works with:
Run-time binding only.
Any type of binding.
Load-time binding or run-time binding.
Load-time binding only.
On a multi-user system, when one user's program goes into an infinite loop:
It keeps running, but no other user's program can run.
It keeps running, interleaved with other users' programs.
The program has to be re-loaded.
An interrupt is generated and the program is terminated.
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" *
One of these is true.
A command-line system is easier to use than a GUI system.
Unix systems rarely have a GUI.
GUIs came before command-lines.
Android's Unix-like command-line was key to its success.
Apple's Unix-like command-line was key to its success.
All users need the command-line.
A command-line system is easier to automate than a GUI system.
What will this Shell script do?
for i in *
do
rm i
done

Remove all the files in the current directory.
Remove all the files in the current directory, except for hidden files.
It is a syntax error.
Remove a file called i, perhaps multiple times.
Remove all hidden files in the current directory.
Remove all the files given in the arguments to the program.
I am in the directory /stuff/and/things and I type: cd ../../../more/things - What directory am I in now?
/more/things
/stuff/more/things
The command is an error.
/stuff/and/more/things
/stuff/and/things/more/things
Linux dominates supercomputers and other specialist computer niches because:
Windows can be customised to unusual hardware.
Unix/Linux pulled ahead in the server market first.
Microsoft does not write for servers.
Open source Linux can be customised to unusual hardware.
Windows Server dominates the server market.
Linux does not dominate that market.
Microsoft does not write for supercomputers.
In a modern OS, one of these is false:
My running program is normally saved to disk when I shut down.
My running program may be in memory at the same time as other programs.
My running program may be scattered in pieces around memory.
My running program may be scattered in pieces around memory and disk.
My file may be scattered in pieces around the disk.
My running program may be in memory at the same time as other user's programs.
My running program is not running constantly, but is getting periodic timeslices of the CPU.
This character should be avoided in Unix filenames:
all numbers
- (dash)
_ (underscore)
. (period)
* (star)
The relationship of Paging to Swapping is:
Disk is used as extra memory. Treated the same as other memory.
Most pages should expect to be swapped to disk as the program runs.
Memory is used as a high-speed overflow of disk, so that the system slows down gracefully rather than suddenly.
They have no relationship. Paging is about memory. Swapping is about disk.
We can predict if running the next program will crash the system with a memory overflow.
Disk is used as a slow-speed overflow of memory, so that the system slows down gracefully rather than suddenly.
This program:
// define a function:
function f() { f(); } // function calls itself
// start the program:
f();

Is detected by the Operating System and terminated.
Runs time-sliced until it crashes by running out of stack space.
Blocks all other processes from running.
Runs forever, time-sliced.
Runs time-sliced until it crashes with a bad memory access.
With compile-time binding, the memory locations used can be changed if the program is re-compiled. Why does the OS not do this?
The source code may not be available.
It would take a large amount of time.
The program may no longer work.
The user's data may be lost.
If a program is not in the directories listed in the "PATH" environment variable:
It can run as normal.
It is a system error.
The OS is broken.
The directory needs to be put into the PATH.
It can be run by typing its absolute file path.
It cannot be run.
It needs to be executable to be run.
This command:
sed -e 's|<|\<|g'
is redirecting output to a file.
is displaying the start of HTML tags but not getting them interpreted.
is blanking out the start of HTML tags.
is removing HTML tags.
is a syntax error.
On a Linux filesystem, block size is 1 k. If you type: echo 1 > file the space allocated for the file is:
3 bytes.
1 k and 2 bytes.
1 byte.
1 k and 3 bytes.
1 k.
1 k and 1 byte.
2 bytes.
2 k.
Which of the following does not take you to your home directory?
cd ~
cd $HOME
cd $HOME/public_html/..
cd
cd .