Wikipedia:Reference desk/Archives/Computing/2008 July 31

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July 31

Exchange server email storage question

How does Exchange Server physically store multiple copies of the same e-mail sent to multiple recipients on the same exchange server? Does it copy each message to each recipient's mailbox, or does each mailbox reference a central storage where the message is only stored once? It seems totally inefficient if an identical message gets sent to everyone on the same exchange server and it is duplicated to every mailbox. So, does a 250 KB email sent to 100 recipients take up only 250 KB of storage space on the exchange server or 25 MB? Onsetocean (talk) 04:57, 31 July 2008 (UTC)

Exchange is a database. Every copy of an email is stored once. --mboverload@ 05:35, 31 July 2008 (UTC)

Microsoft Exchange Server 5.5, Microsoft Exchange 2000 Server, and Microsoft Exchange Server 2003 maintain single-instance storage of messages.

If a message is sent to one recipient, and if the message is copied to 20 other recipients who reside in the same mailbox store, Exchange Server maintains only one copy of the message in its database. [1]

How to Delete the Bookmarks from Firefox and Explorer?

I have hundreds of URLs bookmarked on both Firefox and Explorer, is it possible to delete them in one go? 92.3.71.255 (talk) 05:46, 31 July 2008 (UTC)

Yep!

Internet Explorer: Go to Start>Run and type in %USERPROFILE%\Favorites

Firefox: Go to Bookmarks>Organize>Click on the first bookmark and hold "shift" then click on the last bookmark. Now all between are highlighted. Hit the delete button.

Keep in mind that these are not secure methods to delete the favorites. If you are trying to hide them from ever existing from a truly technical person with an intent to find out we will need to help you a bit more. --mboverload@ 06:35, 31 July 2008 (UTC)

Thanks for that. 92.2.255.73 (talk) 22:02, 31 July 2008 (UTC)

FM Radio

How to prepare a FM Radio ? What instruments are used in it? This is not a homework? Give the picture or chart on how to prepare a FM Radio. 59.92.239.162 (talk) 11:34, 31 July 2008 (UTC)

This may be of interest: http://www.somerset.net/arm/fm_only_one_transistor_radio.html. Blake01 (talk) 11:55, 31 July 2008 (UTC)

Wikipedia won't do your homework for you. JoshHolloway 12:23, 31 July 2008 (UTC)

I fixed your code. The text you want to make bold needs to go inside the three inverted commas, like this.89.241.133.205 (talk) 14:04, 31 July 2008 (UTC)

security of fixed ip addresses

Hi, I've recently signed up for broadband, and my isp has given me a fixed ip address. Is this as secure as a variable address, if people know what it is? Can't they use it to target you in some way? It's Been Emotional (talk) 16:37, 31 July 2008 (UTC)

Looking at this from the other perspective for a moment - there is negligible advantage in having a non-fixed IP address. Firstly they're leased to you on a fairly long term (like a day or two), plenty of time for the hackers to find you. Secondly ISPs allocate dynamic addresses from range blocks and hackers know this and sweep those blocks looking for weak machines. As there's no real security from a dynamic address, that means you're not really worse off having a fixed one. You do need to have a robust firewall, a well maintained computer(s), and the wisdom to avoid doing the silly things on which hackers and other miscreants rely. -- Finlay McWalter | Talk 16:44, 31 July 2008 (UTC)

Thanks for that answer. Does that mean if I have an insecure machine, and the hackers sweep a range of IP addresses, they will know they can find me repeatedly, at least with some reasonable probability of success? It's Been Emotional (talk) 19:03, 31 July 2008 (UTC)

If you have an insecure machine and they find it when they sweep, they'll install software that makes it a zombie slave in their botnet; then they won't have to search for it again - it'll phone home regularly to ask for orders. One chance is all they need. -- Finlay McWalter | Talk 19:04, 31 July 2008 (UTC)

Good grief! Thanks for the warning.... Did you acquire this knowledge from books/ websites, and if so, do you have any recommendations? regards, It's been emotional (talk) 19:20, 31 July 2008 (UTC)

Not the original responder, but here's my advice:

1. If you can imagine it, it's possible for a determined security cracker to do it.
2. Nevertheless, a lot of people seem to be overly paranoid about their computer's security. Running a decent set of antivirus, firewall, and anti-spyware programs (or switching to a different operating system) will likely stop most attacks, simply because typical attackers are looking for the easiest targets.

In other words, unless an attacker uses the unlikely approach of "stalking" your computer in particular, taking basic security measures will greatly reduce the risk of your computer being compromised. « Aaron Rotenberg « Talk « 07:34, 1 August 2008 (UTC)

Thanks again. I meant recommendations about what to read in books or on the net. I'd often like to be independent with these things, but there's such a wealth of info that I don't know where to start. It's been emotional (talk) 06:19, 2 August 2008 (UTC)

Unused elements in an array

I'm relatively new to computer programming and I'm wondering if unused elements in an array can pose a security risk.

for example, the following code generates stats on the inputted text and I initialize an array with 1,000,000 elements that will each hold one word:

Private Sub cmdStats_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdStats.Click
        Dim stats(999999) As Integer
        Dim alltext As String = txtMain.Text
        Dim spaceposit As Integer
        Dim nextspace As Integer
        Dim i As Integer
        For i = 0 To alltext.Length
            If nextspace > alltext.Length Then
                Exit For
            End If
            spaceposit = alltext.IndexOf(" ", nextspace)
            If spaceposit > 0 Then
                nextspace += (spaceposit - nextspace) + 1
                stats.SetValue(CObj(spaceposit), i)
            Else
                Exit For
            End If
        Next i
End Sub

Could the unused elements in this subroutine pose a security risk to my program? It is extremely unlikely that 1,000,000 words will be inputted (which why I made the array so large), so there will almost always be unused elements here. Thanks for the help. Thingg^⊕⊗ 16:59, 31 July 2008 (UTC)

I can't imagine a way to exploit unused elements of an array for an attack. Btw on MS operating systems the security risk from my own programs would be my least concern. 93.132.145.93 (talk) 17:12, 31 July 2008 (UTC)

Unused elements probably aren't a security risk, but the hard limit of 999,999 words might be. You say it's unlikely that anyone will input that many words, but keep in mind that in a security setting you're defending against people who are deliberately trying to break your program. If it's possible to input 1,000,000 words then you might have a security problem—and probably it is, unless Visual Basic strings have a length limit that I don't know about. It would be better to make the stats array grow as needed to hold all the words. That would have the added advantage of wasting less memory: as it is, your stats array will eat up at least 4 megabytes of virtual memory even if the string only contains a few words. I'm afraid I don't know how to make a dynamic array in Visual Basic, but it must be possible. -- BenRG (talk) 17:53, 31 July 2008 (UTC)

I suppose that you can make a dynamic array in VB by just not putting the number of array elements in the brackets. In this case, it would look like this:

        Dim stats() As Integer

If that doesn't work (it might not because you might have to re-declare the array every time you add an element to it, preserving the old contents of the array), then the following should:

        Dim stats() As Integer
        ...
            If spaceposit > 0 Then
                nextspace += (spaceposit - nextspace) + 1
                ReDim Preserve stats(stats.GetUpperBound(0) + 1) As Integer
                stats.SetValue(CObj(spaceposit), i)
            Else
                ...

I'm hoping this should work; I couldn't test it because I don't currently have Visual Studio installed. Hope that helps!  ARTYOM  03:29, 1 August 2008 (UTC)

And, in case you don't already know, attempting to assign elements to a static array beyond the defined length will typically overwrite whatever is in memory after the array, which is more or less random. So, it's not very likely someone could take control of your computer that way, but they could very easily cause the computer to malfunction until a reboot. If you are uncomfortable using a dynamic array, I suggest you add sufficient checks to ensure that you don't assign values beyond the defined length. StuRat (talk) 13:58, 1 August 2008 (UTC)

This is Visual Basic. Array access is bounds-checked, writing past the end of an array is a runtime error, and the worst that should happen is that the program will crash. --Carnildo (talk) 22:27, 1 August 2008 (UTC)

Image viewer for Linux?

I'm trying to find a specific type of image viewer for Linux. It should support the usual image types - JPG, PNG and GIF - and should be usable from the command line just by typing the command followed by the image name. Now here's what I specifically want. The window of the application should automatically size itself to attempt to show the image as near as 100% magnification (1 pixel on screen for 1 pixel in image) as possible. Electric Eyes (ee) back in the days of RedHat Linux 6 did exactly this, but its development has stopped, and the most recent version (0.3.12-5) is dependent on obsolete versions of Gnome libraries, causing it to be incompatible with the latest version of Gnome. Eye of Gnome (eog) is almost what I would want, but it does the resizing the wrong way around - it resizes the image to match the window, instead of the window to match the image. Where can I find an image viewer that does this and is actually supported? JIP | Talk 18:13, 31 July 2008 (UTC)

What about xloadimage or its relative xli? Coming from the good old days before it became cool for programs to do things you didn't ask them to, there shouldn't be any unwanted image resizing. --tcsetattr (talk / contribs) 18:25, 31 July 2008 (UTC)

QIV (http://www.klografx.net/qiv/index2.html) seems to do everything you want. - Sorf^ane 18:38, 31 July 2008 (UTC)

Yes, thanks. If the image is smaller than the screen size, this works exactly as I want. But if the image is larger than the screen size, it still doesn't work exactly right. Good old Electric Eyes (damn, I miss it) made its window the full screen size and offered scrollbars. QIV, on the other hand, insists on a 100% magnified window, so it makes it bigger than the screen, requiring me to hold Alt and drag the mouse to scroll the image. Oh well, I guess I may be able to live with that. JIP | Talk 18:46, 31 July 2008 (UTC)

xli, when given an image bigger than the screen and no additional options, creates a window that's 90% of the screen size and lets you scroll around. (No scrollbars, just drag any point on the image to where you want it to be within the window) --tcsetattr (talk / contribs) 18:53, 31 July 2008 (UTC)

xli was a bit difficult to find. A Google search for the name gives thousands of entirely unrelated hits. It's not even available for my distribution (Fedora 9), but an RPM package for Mandriva worked fine. I hate to keep nagging and reminiscing about Electric Eyes, but there's still one thing. Electric Eyes, Eye of Gnome, and QIV all support viewing multiple images one at a time, only requiring a mouse click to move to the next image. xli doesn't seem to do that. Or do I just not understand how it works? JIP | Talk 19:06, 31 July 2008 (UTC)

If you give xli multiple filenames (like "xli *.jpg") you can use "n" to move to the next image and "p" to move to the previous image. It has other keyboard commands you can read about in the man page... scrolling around in an image that's too big for the window is the only thing you use the mouse for. --tcsetattr (talk / contribs) 19:23, 31 July 2008 (UTC)

Oh, thanks. It works. I guess I should have RTFM. =) I hate to keep saying this, but quoting Columbo, there's still one thing. Pressing n at the last image quits xli. I would have wanted it to stay at the last image. Otherwise it works fine. JIP | Talk 19:25, 31 July 2008 (UTC)

Another option not mentioned yet is xzgv. It's a little more "modern" (i.e. it has menus) but it also seems to fit your requirements so far. And I just discovered, in xzgv you press the space bar to go to the next image. When you're on the last image, space bar does nothing. --tcsetattr (talk / contribs) 19:39, 31 July 2008 (UTC)

Microphone is not working

I recently got a VoIP account and set up Ekiga on my Fedora 9 system to use it. Now I can call the VoIP account from a normal phone, and the other way around, all fine, and I can hear sound from my speakers all fine. I just can't transmit any sound.

I bought a simple Logitech desktop microphone and plugged it into the mic socket of my motherboard's integrated soundcard (shown as "nVidia Corporation MCP61 High Definition Audio" on hwbrowser) and tried to speak to it in Ekiga. Nothing happened. I tried the same in Sound Recorder. Nothing happened. It's as if the microphone wasn't even there.

I asked the shop who sold me the microphone, and they asked me to first check the BIOS settings to see if the whole soundcard is enabled. I told them I can hear sound all fine, just not transmit it. So they thought the soundcard itself is OK, the problem is with the drivers. How can I see if I have the correct drivers, and if not, where can I get them? By far the most commercial vendors of computer components don't know Linux exists, or if they do, they make a public statement about not supporting it.

The weirdest thing is, when I am on a call in Ekiga, merely speaking (or making any kind of sound at all) near the computer causes the speaker volume meter in Ekiga to change. Even if both the microphone and the speakers are unplugged. It still doesn't transmit any sound, though. Is the soundcard itself somehow picking up the sound, or am I being haunted? JIP | Talk 18:48, 31 July 2008 (UTC)

I can't speak for Fedora, but Ubuntu's (I guess Gnome's) sound manager lists a bunch of "devices", which correspond both with real audio devices, and with the various audio interfaces (ALSA, OSS). My first guess would be one of:

• your Ekiga is set to have its input device on the wrong audio input or an incompatible sound system (so mess around)
• your mic is muted (by software, in the audio control panel)
• your mic is unmuted but its (software again) audio level is turned way down
• there's a little "mute" switch on the mic or its cable that you didn't notice
• (please don't be insulted) you plugged it into the wrong hole

Audio support on the sound capabilities integrated into nVidia nForce is pretty good, and if you can emit sound on the same device then I don't think the driver is bad. -- Finlay McWalter | Talk 19:13, 31 July 2008 (UTC)

The three things you listed about muting and volume control were the first things I checked. Nothing is muted, every volume level is at maximum. Still no sound transmitted. I think I tried every device Gnome is listing, but I'll have to check again. As for the wrong hole, I think it was the right one. The plug is pink and the socket is pink. The whole point in colouring plugs and sockets is that the same colour of plug goes into the same colour of socket, isn't it? JIP | Talk 19:20, 31 July 2008 (UTC)

Google Translate

As of now, Google Translate appears to, when translating from English to Croatian, translate American Idol to Home Loan Lender. Does anyone have any idea why this happens? Bart133 ^{(t) (c)} 18:52, 31 July 2008 (UTC)

Both terms refer to the worst things imaginable. --mboverload@ 18:58, 31 July 2008 (UTC)

Home Loan Lender is composed of three words, none of which are Croatian. They are the two worst things imaginable, but why would Google translate it that way? Bart133 ^{(t) (c)} 19:05, 31 July 2008 (UTC)

I have no knowledge of what's happening on Google's servers, but if I had to guess I'd say it's probably caused by people abusing the "suggest a better translation" feature. (Either intentionally or by accident.) If you know Croatian, Perhaps you could help them fix it the same way? APL (talk) 03:50, 1 August 2008 (UTC)

Google Translate for Finnish is causing me constant amusement. Not only does it introduce English words when translating between Finnish and a non-Finnish, non-English language, it somehow keeps translating the names of many Finnish cities to names of Thai cities. It also keeps translating things like I understand to en ymmärrä ("I don't understand") and referring to women as "he". I suspect that even with the automatic learning from human translators implied by the "submit a better translation" offer, it has decades to go before it can produce Finnish a native speaker could even remotely accept. The same must be true for Croatian. JIP | Talk 19:09, 31 July 2008 (UTC)

The google translator has been known to do things that are far, far weirder than that. The explanation is that the translation engine doesn't work with dictionaries, it works with huge amounts of text that appear in two languages and it compares them. Occasionally, the texts aren't identical, and it gets confused. ADFSGL (talk) 12:59, 1 August 2008 (UTC)

Volume Control/Sound Recorder Missing!!!

I had the little speaker icon on the tray off to save resources, but when i needed it back on again, my computer couldn't find the program. Message Was: "Cannot find sndvol32.exe. Reinstall it under Add/Remove programs in control panel." But when i went to Add/Remove programs, there wasn't anything about sndvol32.exe anywhere. I also found that sndrec32.exe is missing as well. I was under the impression that both programs are necessary for windows to function. Help Me! BTW: System is an old Dell Inspiron running Windows XP SP1. Has 96 MB of RAM with a 457 MHz Processor (yes it is a crappy system) Help! 31306D696E6E69636B6D (talk) 19:45, 31 July 2008 (UTC)

The official Microsoft solution is: http://support.microsoft.com/kb/319095 but this requires the XP CD and I dont know if you have that at hand. I'll find an alternative in a minute for you - Sorf^ane 19:52, 31 July 2008 (UTC)

Found sndvol32.exe - http://forums.techguy.org/attachments/91688d1163267820/sndvol32.zip. Be sure to virus scan before extracting it to C:/Windows/system32. - Sorf^ane 19:55, 31 July 2008 (UTC)

funky diff options

I want a diff program with two special options for when it's recursively comparing all files in a directory tree:

1. If two files are both symbolic links, say whether they do or don't point to the same place (as opposed to comparing the contents of the files pointed to, which of course is the default).
2. If two files are both device special files, say whether they are or aren't the same device (both block or both character, same major and minor numbers).

I find that GNU diff (at least the versions I've checked so far) doesn't have this options (which surprises me, since GNU software usually has all the obscure options you could ever want, as well as some you don't :-) ).

Perhaps I'll just add these two options to GNU diff. (Neither should be hard to implement.) —Steve Summit (talk) 20:21, 31 July 2008 (UTC)

Perhaps the comparison mode of tar would be useful, as demonstrated here:

 $ ls -l test1 test2
 test1:
 total 0
 crw-rw-rw- 1 root root 1, 3 Jul 31 15:30 null
 lrwxrwxrwx 1 root root   11 Jul 31 15:31 passwd -> /etc/passwd

 test2:
 total 0
 crw-rw-rw- 1 root root 1, 5 Jul 31 15:31 null
 lrwxrwxrwx 1 root root   11 Jul 31 15:32 passwd -> /etc/shadow
 $ (cd test1;tar cf - .)|(cd test2;tar df -)
 ./null: Device number differs
 ./passwd: Symlink differs
 $ tar --version
 tar (GNU tar) 1.16

Of course you'd still have to call the regular diff program if you want the usual output for regular files, but if you're not interested in that part... --tcsetattr (talk / contribs) 20:36, 31 July 2008 (UTC)

Ah, good suggestion! And in the case I was interested in today, one of the directory hierarchies I was interested in had started out as a tar file, so this would be easy.

Unfortunately (a) I am interested in the detailed differences between regular files if there are any, and (b) tar -d has this annoying gap (or did, last time I looked) of not reporting files that are in the directory but aren't in the tarfile. (Some day I've got to resurrect the tar -d code I wrote in 1985 or so that did this correctly, and see if I can wedge it into gnu tar.) —Steve Summit (talk) 20:46, 31 July 2008 (UTC)

Mouse sensitivity shortcut for Ubuntu

I have a low resolution mouse. The cursor jumps on the screen many pixels at once. Usually I have no problems with it, but resizing windows can sometimes be a pain. On Ubuntu Linux/Gnome can I set a keyboard shortcut to slow down the cursor temporarily? (I know of alt-f8, but it apparently only helps for the "top level windows".) --212.149.216.13 (talk) 20:31, 31 July 2008 (UTC)

Quad-core processors

(moved from SciRef desk) Franamax (talk) 23:02, 31 July 2008 (UTC)

how do quad core processors work? —Preceding unsigned comment added by 24.140.68.142 (talk) 20:38, 31 July 2008 (UTC)

I don't know if it will be specific enough for your question, but we do have an article on Multi-core processors in general. --Allen (talk) 20:46, 31 July 2008 (UTC)

Stupid-Simple answer: 4 processors on 1 chip that work together to share the load. I suggest you read the article that Amcbride so nicely linked for you =) --mboverload@ 03:34, 1 August 2008 (UTC)

Windows Mobile/AAC

What software (preferably free) can I use to play AAC (m4a) audio on a Windows Mobile 5 smartphone (Pantech PN-820; not a Pocket PC)? ~~ N (t/c) 23:30, 31 July 2008 (UTC)