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Write two programs that simulate two versions of a paging memory management system - one based on FIFO algorithm, another one based on LRU. Make the following assumptions:
the size of the internal memory is 40K, and it is divided into 10 page frames;
the system loads and runs one process; the length of the process is 80K (thus, it is to be divided into 20 pages).
Your driver program will be a loop running 40 times. On each run of the loop, it randomly generates a reference to a page in the process (a number in the range from 0 to 19) and makes sure that the referenced page gets a page frame. The driver will count and print out the total number of page faults; every time when a page fault occurs, it will print out the number of the page that caused the fault and the number of the page frame it gets.
Run the driver program first time using the FIFO memory management system and save the reference string generated by the driver. Then run (a slightly different) driver program, using the LRU. Compare the numbers of page faults occurred in both cases.
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And? What's the question?
Dave Kreskowiak
Microsoft MVP - Visual Basic
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Oh look, someone wants their homework done for them. Try Rentacoder.
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hello!
can anybody guide me how to change windows-xp administrator or guest password from its registry
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You cannot get the password but you can reset the password. You'll need a boot CD with some tools on it to do this, like ERD Commander, or some other tool, possibly even UNIX-based, to do it.
Dave Kreskowiak
Microsoft MVP - Visual Basic
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thanks.
could you please tell me in some detail how to do all that using bootable cd.
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You'll have to read the docs for the app CD you get.
Dave Kreskowiak
Microsoft MVP - Visual Basic
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Hi,
my problem is the following - I have some files that my application is using.
these files are valueable and I want to protect them from being copy by the user.
the state is this:
the application is installed only in my company on some computers.
the users are not administrators.
I can't put the files in the server because they are being used locally by the application and they are very big, around 800MB.
I need somehow to prevent copy/burn/whatever for the user but allow a read permission for my application.
how can I do it?
thanks.
Alon
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There's no way to do that. Since the application runs in the security context of the suer that launched it, it needs Read permission to, obviously, read the data file. Read permission is the only one a user needs to copy a file to another location. There's no way to prevent it.
Dave Kreskowiak
Microsoft MVP - Visual Basic
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that is what i thought and was afraid of...
but maybe there's some third party solution - somekind of lock folder utility that cab accessd through command line (with parameters) that my application will be able to unlock but user won't be able to.
thanks anyhow.
Alon
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That won't work either, because all the user then has to do is launch your application (or run the utility to unlock it), switch back to the Desktop and copy the file.
Dave Kreskowiak
Microsoft MVP - Visual Basic
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how would he do that? he won't have the password.
Alon
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What password?? You can't protect a single file or folder with a password. NTFS doesn't support it.
Dave Kreskowiak
Microsoft MVP - Visual Basic
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Security is based on user accounts, not applications. If you remove the read priv from the file, no app you run can read it, including the one app that needs to read it.
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Like stated in the previous posts, there is no way to prevent the user from making a copy of the file if the app runs with the user's context. You could, however, encrypt the data-file. Depending on the encryption technique, there is a possibility of your application working significantly slower than before.
Additionally, the decryption routine AND the decryption key kave to be somewhere in your application (which is stored on the users computer). Thus, it is possible (though maybe not feasible) for the user to obtain these (by disassembly).
I believe what you NEED is a good licence agreement (ask a lawyer). This will not enable you to entirely prevent spread within one company, but will give you additional legal leverage if you discover that your data files have been sold to others (e.g. competitors).
Cheers,
Sebastian
--
Contra vim mortem non est medicamen in hortem.
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If this is an intranet only app, make it client server with the full dataset only stored serverside.
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Rules of thumb should not be taken for the whole hand.
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first of all - thank you all for replying me.
let me be more specific -
I know that the regular OS capabilities do not let me do that, what i'm looking for is some thiord party solution like "Cryptainer PE" or "Lock Folder XP" that will give me a command line option to access the encrypted files but won't really put them out to a shared/visible folder.
BTW, the 'place files on server' solution is obvious but not suited for me as I have a lot of files and each is very big.
BTW2, my application is working in my company and the users are my employees. It's not for a commercial use but for private use by the company.
I hope things are a bit more clear now.
Alon
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OK, I got the solution - http://www.everstrike.com/shield.htm[^]
it gives the option to hide the files and also i can define a list of applications that can have an exception and will be able to see it.
Alon
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based on a quick glance over, that appears to be a whitehat(?) rootkit. It may work now although using any such software will result in increased vulnerability to hidden malware as well, but MS has locked down win64 to prevent that sort of meddling, which means that there's a significant chance your app will cease to work following upgrades in several years.
--
Rules of thumb should not be taken for the whole hand.
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what is "whitehat rootkit" (english is not mother tongue...)
and thanks for your concern but as I developed the application I have the ability to change it according to future use.
for now this solution is suitable for me, unless you have a better one.
Alon
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A root kit is a program that modifies the behavior of the operating system by injecting itself into the kernels execution path. These are often used by the more destructive malware programs to conceal themselves from adware/trojan removal tools. The name comes from the fact that the originals were used to steal root passwords for unix systems.
Whitehat means a good guy, and dates back to old black and white cowboy movies. The villain in contrast would always wear a blackhat. In modern IT useage, blackhats are virus writers and system hackers, and whitehats are the people who try and prevent them.
Depending on your organizations IT policies you might need to get approval from them in order to deploy this sort of solution since it would also provide a way for hostile applications to hide in your systems. At a minimum you need to let them know about it so it's not mistaken for malware in a security audit.
--
Rules of thumb should not be taken for the whole hand.
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Thank you very much for the detailed explanation.
I will consult my IT manager about the software.
Alon
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Alon Ronen wrote: I need somehow to prevent copy/burn/whatever for the user but allow a read permission for my application.
I think you should physically remove the device that could copy your file to the other storage device such as USB, Floopy disk, CDRW...
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Is there any difference in the privileges of the 'localsystem' account under XP,2000 and 2003 server?
We are launching a browser from an INTERACTIVE windows service (running under 'localsystem' account),and make it navigate to a url.
The url in turns redirects to another page.
This navigation/redirection is allowed in 2000 and XP ;but fails in 2003.
Is this a result of difference in network privileges for localsystem account?
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The LocalSystem account doesn't have network priv's. It also has it's own copy of the default IE configuration, which you CAN NOT CHANGE! Since Windows 2003 locks down IE access from the server to the otuside world, it's essentially crippled. You CAN NOT make any changes to it's configuration since you can not login as the LocalSystem account and change its settings.
This should be done using other methods, not a browser control, and using an account setup specifically for your service without any interaction.
Dave Kreskowiak
Microsoft MVP - Visual Basic
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