Wikipedia:Reference desk/Archives/Computing/2008 April 19

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[edit] April 19

[edit] going away for a few weeks but i'd like access to my windows pc, any freeware to do that?

my wife is staying home and the computer will often be on. i think it's behind some firewalls or something, I want it to actively poll and initiate a session to me so i can use a remote desktop somhow...is there any way to do anything like that? basically, it would be the same thing as 'back doors' a hacker would install except that I want to do it myself, but prefereably so no one else can connect too. :) thank you for any advice you might have.

Windows comes with a Remote Desktop client built in. Google "Windows Remote Desktop" and you'll find info on how to set it up (e.g. here). --Captain Ref Desk (talk) 00:25, 19 April 2008 (UTC)
I'm not entirely sure about a 100% freeware version, but I know that Kim Komando generally offers a 60-day free trial of GoToMyPC.com during the commercials in her shows – with a promo code. crassic![talk] 01:46, 19 April 2008 (UTC)
VNC is free and easy to use. My favorite was TightVNC, which allows you to see your remote computer (in this case, your home computer) in a VNC client or a web browser. Other VNC clients probably have similar functionality. Besides the browser option, there are VNC clients for non-Windows computers as well. As for firewalls, you will need to find an open port for VNC to broadcast on (VNC's defaults are 5800 and 5900). ShieldsUP (scroll down that page) is a quick way to identify your open ports. / edg ☺ ☭ 02:12, 19 April 2008 (UTC)
You can use a free service called LogMeIn . It provides you with some advanced features such as chatting with the host and file transfer as add-on premium services, but the basic desktop sharing is free. 12:35, 19 April 2008 (GMT +0400)

[edit] code

What have I done wrong here?Failed to parse (PNG conversion failed; check for correct installation of latex, dvips, gs, and convert): \iiiint_{\delta\gamma}^{\hat\mathbf{H}i}\ \mathrm{d}x=\oint_{\pi^i}^{{e^-i}^x^2}\ \mathrm{d}\overrightarrow{\phi} Zrs 12 (talk) 01:39, 19 April 2008 (UTC)

See this for help. Basically, you probably don't have the required programs. -- kainaw™ 02:32, 19 April 2008 (UTC)
Actually, the parse error is caused by the {{e^-i}^x^2} part which needs some more braces for grouping. The ^ operator is nonassociative, so you can't say a^b^c; you need to specify a^{b^c} or {a^b}^c
By adding braces around x^2 I get this:
\iiiint_{\delta\gamma}^{\hat\mathbf{H}i}\ \mathrm{d}x=\oint_{\pi^i}^{{e^-i}^{x^2}}\ \mathrm{d}\overrightarrow{\phi}
which may not be right (I have no idea what it means) but at least it passes the parser. --tcsetattr (talk / contribs) 03:09, 19 April 2008 (UTC)
I don't know what it means either. I was just messing around in the sandbox. Zrs 12 (talk) 15:01, 19 April 2008 (UTC)

[edit] Blogger and Adsense

I've just started a blog and I saw that you can have advertising on your blog through a service called Adsense and that they'll let you wet your beak in some of their revenues. So, I pushed the appropriate buttons and received an email asking me to send through a form specifying how any payments should be made. There the problems began. The Google Adsense account form only shows fields for residential addresses. It also mandates that a contact phone number be provided. I do all my business through a PO box address for security reasons. If someone was going to post me a cheque I'd surely want it to go to a secure address. Further, I'm not all that mad about sending off my home address or any phone number to Google. I can't think of any speck of a legitimate reason why they need either. They have all the controls in their hands already: why do they need personal data? The "help service" on their site just takes you in circles on this one. Can anyone enlighten me here? Is there way around this? Retarius | Talk 03:33, 19 April 2008 (UTC)

Without specifically addressing all of your concerns, I can say that after four years of blogging I've not received a penny from adsense, so unless you have a blog that draws tons of visitors (and/or visitors who click links), then setting up adsense is probably a waste of time. --LarryMac | Talk 05:44, 19 April 2008 (UTC)
In my business, it's a requirement of the so-called "PATRIOT Act"; we have to have a legal address and a mailing address for every client, and the legal address cannot be a pobox. In this manner, our government regulators are assured that we're not facilitating money-laundering, or somehow doing business with terrorists. (How this is proved by this regulation I don't know, but them's the rules, and we plays by them!)
Danh 63.226.145.214 (talk) 21:58, 20 April 2008 (UTC)
Thanks, guys. I'd still like to give Adsense a go. At least you've enlightened me on the prospects for profit and the reasons behind the style they use for their form. Retarius | Talk 05:34, 21 April 2008 (UTC)

[edit] C/C++/Java/WhatHaveYou prefix/postfix increment

Even after many years I'm still sifting through countless examples of people using postfix (not sure if that's the right term) increment or decrement when it's not necessary. Is there some kind of psychological reason why people insist on saying "i++" instead of "++i" when they don't intend to use the old value?

I can understand some underlying reasons to prefer prefix. Like when your C++ compiler doesn't do, or has disabled, optimizations, or when your class overloads the operation a la "MyClass& operator++()" vs "MyClass operator++(int) const". Java is beyond me (I don't know much about the runtime optimizer). I have even less faith in a JavaScript implementation's ability to optimize-out unused return-values. Where did this abundance for postfix increment start?

Pet peeve, comment at will :) --Silvaran (talk) 07:52, 19 April 2008 (UTC)

I just think that it's an aesthetic thing, I personally think "++i" just looks strange. It's probably a case that i++ is more widely used because it's more widely used, i.e. since that's what most people see i++ when they read other people's code, they type it themselves. Optimizing on the level of "i++" or "++i" is honestly a little silly, I mean what are we talking about here, something on the order of one cycle? Unless you are writing for MIX, who the hell really cares? 83.250.207.154 (talk) 09:06, 19 April 2008 (UTC)
Maybe people see the name "C++" as an endorsement of this style. Personally I used to write "i++" because it looked more consistent with "i += 2", but I switched to "++i" because of the issue with iterators. Any modern C compiler will compile "++i" and "i++" into exactly the same code when they appear in a void context, probably even when all optimizations are disabled (yes: I just checked this with gcc and VC++). I suspect this was already true of the earliest K&R implementation. This also goes for C++ when "i" has a builtin type. I assume it's also true of Java and JavaScript and every other language that has this idiom. -- BenRG (talk) 12:57, 19 April 2008 (UTC)
Are you suggesting a pre-fix operator is faster than a post-fix operator? I can't imagine why it would be. Maybe it's just personal preference, but ++i just looks weird to me, so much so that I will sometimes change it to i++ unless the context demands the pre-fix operator. My other pet peeves that make code harder to read and maintain: putting the "{" at the end of a line instead of putting it on its own line; too     much      spacing      between      operators; poor indenting; and so on. Astronaut (talk) 15:04, 19 April 2008 (UTC)
Yes, the prefix operators can be faster. The postfix operator requires that the value of the variable be captured, the variable incremented, and then the old captured value used. This probably isn't a big deal for built-in types, but when the operator is overridden, it can become more of an issue (especially because keeping similar semantics for user-defined types can often mean the difference between returning a reference to the original instance vs. making a temporary copy of the object). I personally don't have an aesthetic preference, so I have built the habit of using the prefix operator any time I don't really need the old value. --Prestidigitator (talk) 17:46, 19 April 2008 (UTC)
Postfix is taught before and more often then prefix. Also, linguistically, I would hazard a guess that x++ functions more places then ++x does. I know a few interpreted languages for which neither has any actual significance (besides saving the bother of typing x = x + 1), which only support the latter syntax. Ironmandius (talk) 00:24, 23 April 2008 (UTC)
This may not add anything to the conversation, but I'm big on useless tidbits :-)...
The syntax exists in the first place because the hardware on which C was first developed (PDP-8?) had an "Increment in memory" instruction: it was not necessary to do a Load/IncrementRegister/Store sequence to increment a variable. This bought you a "free optimization", so to speak. --Danh 63.226.145.214 (talk) 22:06, 20 April 2008 (UTC)

[edit] Looking for a nice, high-quality, free midi synthesizer

I have a whole lot of MIDI files. They used to sound rather nice with my old offboard sound card. On my new computer, they sound terrible (like midis should, they say). Are there any free, high-quality midi synthesizers out there I could use? I used to have Wingroove around, and it would install itself as a MIDI playback driver. I was looking for something like that... — Kieff | Talk 07:57, 19 April 2008 (UTC)

Assuming you use windows - check that your MIDI player is configured to use Microsoft GS Wave-table Synth - I found that it has a surprisinly decent quality. Your MIDI player might have defaulted to a sucky synth-set with bad samples that comes with your sound card. Something else to check - certain MIDI files created with a "General Midi" (GM) device such as a Roland won't sound that great with GS so you might have to switch synth-sets; however I've found this to be an exception rather than a rule. Sandman30s (talk) 16:50, 19 April 2008 (UTC)
If your new computer has Vista, check for updated Vista drivers for the soundcard. I have read that some soundcard drivers have not yet been updated for Vista, so only the default drivers end up being used. Astronaut (talk) 17:20, 19 April 2008 (UTC)

[edit] web-based MRI file viewer

Is there a web-based way to view 3D MRI scans? Something like MRIcro but able to be run off of a browser client? Just curious... --98.217.8.46 (talk) 13:01, 19 April 2008 (UTC)

[edit] Boot Camp Keyboard

When I use Boot Camp to run Vista, (-_-) my keyboard suddenly doesn't work! It can eject disks, but no typing. How can i fix this to make the keyboard work again? --Randoman412 (talk) 15:01, 19 April 2008 (UTC)

Don't run Vista. Useight (talk) 16:21, 19 April 2008 (UTC)
Hardly a helpful response. Astronaut (talk) 16:50, 19 April 2008 (UTC)
A less helpful response. Useight (talk) 19:44, 19 April 2008 (UTC)
Never mind, now the keyboard works. (P.S. i don't want to run Vista either, anyone have an XP disk? (I'm Kidding)) --Randoman412 (talk) 19:24, 19 April 2008 (UTC)
TigerDirect has WindowsXP Pro for $139.99. Useight (talk) 19:44, 19 April 2008 (UTC)
Do you have `five on it`? Come into Russia - we have plenty of OS installation disks for a humble price of a 5 dollar each... ^_^

[edit] Camera behind video display

The problem with talking and using a webcam is that both parties can't look at each other's image and directly into the webcam at the same time (if they don't look directly at the webcam, their eyes appear to be averted from you). Is there a technology that would allow the camera to go behind the screen? ----Seans Potato Business 15:53, 19 April 2008 (UTC)

Professional studios use angled glass so that presenters can read the autocue and look right down the lens of the camera at the same time. I guess you could rig something similar - angled glass in front of the screen, the webcam to one side, above or below, and a darkened room or hood to cut down on stray reflections - but it sounds like a whole load of trouble to go through. Astronaut (talk) 16:48, 19 April 2008 (UTC)

[edit] Random rebooting

Hi, my single-core P4 computer has suddenly, for the last two weeks, developed the habit of rebooting randomly straight into POST (bypassing even a blue screen) - I'm using XP SP2. It reboots only when I am using a graphics intensive application such as a movie or game, and only after a random amount of time - minutes or hours. I've done a thorough virus and spyware check, and done various burn-in tests, and checked the windows system events but since these are clean 'resets' they don't even register in Windows. I've also upgraded my nvidia to the latest, then reverted to 162. I've reinstalled DirectX. Any other ideas please? Sandman30s (talk) 16:43, 19 April 2008 (UTC)

This is one of the most difficult computer problems to solve. However, the process is simple:
  1. Get a new power supply. If you have a 300W, get a 500W. If you have a 500W, get a 700W. Just get more power capability in your system.
  2. If that doesn't fix it, disconnect everything that isn't necessary: CD drive, floppy drive, second hard drive, sound card, network card, second/third stick of RAM...
    • If that fixes it, put it back in one part at a time until you figure out what is causing the problem.
  3. If that doesn't fix it, get new RAM.
  4. If that doesn't fix it, get a new video card.
  5. If that doesn't fix it, get a new hard drive (copying your system from the old one to the new one).
  6. If that doesn't fix it, get a new motherboard and CPU.
  7. If that doesn't fix it, get a new case.
I had to go all the way to the last step once. The case itself was causing hard drive corruption and random rebooting. Like I said, it is a difficult problem, but a simply process of elimination. -- kainaw™ 18:13, 19 April 2008 (UTC)
Sigh - all these 'get new' scenarios are not only costly, it will mean sourcing older components. I was thinking about getting a whole new computer anyway, so spending more on a four-year old system might not be wise. So you think it's unlikely to be a software or hardware problem with the graphics card - since it reboots ONLY when using graphics intensive apps? Sandman30s (talk) 21:08, 19 April 2008 (UTC)
The case was causing the problem with the hard drive? The only problem I can forsee a case causing is poor airflow. Or maybe a short. Useight (talk) 19:42, 19 April 2008 (UTC)
And even if it were the case - how would you diagnose that? Tell us the full story, Kainaw! --90.209.36.146 (talk) 20:45, 19 April 2008 (UTC)
I put the new power supply on top because that is the most likely culprit. Video cards suck a lot of juice and if you are maxing out the hard drive while maxing out the video card, you are asking for a drop in power to the point that the computer loses power and reboots.
I usually think it could be a fan (overheat) issue. However, I've never found that to be the problem. You can try replacing the fans if you like.
As for the case... this is a VERY weird problem. I was asked to fix a computer that constantly got hard drive corruption. I replaced the drive - still got corrupted. I replaced the drive (again) and cables. Still got corruption. I removed everything but the essentials. Still got corruption. I swapped out everything (motherboard, power supply, and all drives). Still got corruption. I put the owner's original parts in a new case. No corruption. I asked the owner if ANYTHING at all happened before this problem. He said that he cleaned out the dust inside the case. Is that all? He said there was a lot of hair from his cat. Is that all? He said he removed a little sheet of aluminum foil... That wasn't aluminum foil. It was lead foil that sat between the case speaker and the hard drive chassis. Without it, the magnet on the back of the speaker was so close to the hard drive that it was causing random drive corruption. -- kainaw™ 21:16, 19 April 2008 (UTC)
Thanks for all the insight Kainaw. I'm not so sure about the power supply since it's been running like that for years. The overheating might just be the problem - maybe I can test that by placing a room fan next to the open case - sounds silly but it does cool things down! Sandra reports my hard drive as running too hot. My 7900GS is showing 58 degrees celcius. BTW would you recommend 400W power supply for a powered 7900 GS, two SATA drives and a dvd writer? Sandman30s (talk) 21:36, 19 April 2008 (UTC)
OK, I've cooled it down with a fan and it still reboots. Tried again and it seems to be getting worse - rebooted after 1 minute of watching a movie. My system monitor shows the system fan to be at 0 RPM - however I can physically see the system fan spinning so I'm not sure if a sensor is down or something. I hope it's not the video card as that is likely out of warranty. Ugh. Sandman30s (talk) 22:51, 19 April 2008 (UTC)
All 400W PSUs aren't the same. You need to consider the number of amps that can be supplied on each of the rails. After problems with cheaper units, I use a Thermaltake Toughpower and whatever problem it was that I was having at that time went away. --Seans Potato Business 06:59, 20 April 2008 (UTC)
Also some power supplies are notorious for being underpowered and breaking down or blowing up at random intervals. Nil Einne (talk) 19:49, 20 April 2008 (UTC)

[edit] gaming

i recently downloaded the demo to the strategy game caeser 4 from its official site. there were no problems during the download and installation but now everytime i click the icon the computer restarts and a disc check occurs and a message box says that the computer has recovered from a serious error . HELP --scoobydoo (talk) 16:58, 19 April 2008 (UTC)

Looks like the game is causing the computer to crash. The disk check, "serious error" message stuff is usual for crashes. Do all the usual checks for viruses and spyware, make sure you have the latest updates, etc. Check the game's forums (if any). Find out if the same problem exists on another computer. But best advice: don't run that game again. Astronaut (talk) 17:15, 19 April 2008 (UTC)
It's supposedly not a very good game, anyway. · AndonicO Engage. 12:44, 20 April 2008 (UTC)

[edit] Error Messages

On Windows XP, how do you set it to show unabridged error messages? Zrs 12 (talk) 19:59, 19 April 2008 (UTC)

Is that possible? Can you give a specific situation that you'd like that to happen? Gary King (talk) 20:24, 19 April 2008 (UTC)
It is possible (see http://www.andybrain.com/qna/wp-content/uploads/2007/10/strange-error-1.jpg), but I'm not sure that's on the XP OS, although it is obviously on some Windows OS. And I have not a specific situation, all situations would be good though. Zrs 12 (talk) 20:37, 19 April 2008 (UTC)

[edit] usb hard drive not giving itself a drive letter

I was installed ubuntu the other day and accidentally chose to install it on my usb drive which was plugged in and happens to have same hard disk space as my regular drive. soooo...I caught my mistake "in time" and didn't put ubuntu on the usb drive, but the formatting was all ready to go and it may have half-completed is my guess.

So now I'm back on my windows XP pro OS (same machine). I plug in the USB and everything goes like clockwork, "USB detected" "maxtor x.x..x found" "mass storage device detected" etc. the drivers are in the fine, it's clearly communicating, but when I go to "My Computer" it hasn't assigned itself to a drive letter....so I don't know how to access it.

Like I said, I'd reason to guess that I screwed up the formatting just enough to not be able to access to reformat it and make it right. I'd like to recover the data (futurama backups) but no big deal if I can't. Any ideas for ubuntu or xp to fix this? Thanks.

It is probably formatted in ext3 - which Windows won't assign a drive letter to. I avoid Windows as much as possible, so this is from memory. Click start-run. Type compmgmt.msc. Go to diskmanagment. You should see the drive and be able to format it to a Windows typed drive. If those commands are not exactly correct, perhaps the next person here will know the proper spelling. -- kainaw™ 21:21, 19 April 2008 (UTC)
That will work, but it's faster to run diskmgmt.msc, which opens the disk manager directly. -- BenRG (talk) 22:27, 19 April 2008 (UTC)
fascinating! Thank you both

[edit] Javascript image preloader

I've written up a web app that needs to be able to load a number of images before it lets the user view the page. (No, this isn't a regular website or anything; it's a very specific web app that will only be used by one person. So don't lecture me on web design! ;-)

The site uses PHP and Javascript together. I have all of the image paths dumped into the HEAD of the HTML in an array like the following:

var doc_tag = new Array();
doc_full[1]="152509.pdf.full-0.png";
doc_small[1]="152509.pdf.thumb-0.png";
(etc.)

On the page itself, I have a DIV that sits on top of everything else and says "Loading..." The goal is to preload all of the images and then remove the "Loading" DIV only then. So in the ONLOAD of the BODY element of the page, I call a function called precache() which is the following:

function precache() {
        var preload = new Array();
        for(i=1;i<doc_small.length;i++) {
                preload[i] = new Image();
                preload[i].onLoad=imageLoaded();
                preload[i].src = thumb_dir+"/"+doc_small[i];
        }
}

Which seems like the usual way the web says to preload things. The "onLoad" function of the preload images then does the following:

function imageLoaded() {
        preload_count++;
        document.getElementById("cachestatus").innerHTML = "Thumbnail "+preload_count+" of "+(doc_small.length-1);
        if(preload_count>=doc_small.length-1) {
                hideloading();
        }
}

"Cachestatus" is just a little SPAN on my "Loading" DIV. preload_count is a global variable. hideloading() is just a function that hides the "Loading" DIV.

Now all of this seems like it should work to me, but it don't. 1. the "cachestatus" SPAN never updates, 2. the page is displayed before all of the images have preloaded. Usually MOST of the images have preloaded but clearly not all of them.

So... what am I doing wrong? Any thoughts? Better way to do it? --Captain Ref Desk (talk) 20:49, 19 April 2008 (UTC)

The more I play with it, the more I get the picture that Firefox (and Safari) trigger the onLoad event of the Image object long before it actually loads the image. (I've tried reversing the order of the SRC assignment and the ONLOAD assignment; it changes nothing). Thoughts? It certainly seems irregular/incorrect. --Captain Ref Desk (talk) 02:59, 20 April 2008 (UTC)
This line: preload[i].onLoad=imageLoaded(); assigns the value returned by a call to imageLoaded(). You want to assign the function itself, instead of the value returned by a call to it. I.e. lose the parentheses: preload[i].onLoad=imageLoaded; Weregerbil (talk) 10:50, 20 April 2008 (UTC)
Great, thank you! That was driving me CRAZY. --Captain Ref Desk (talk) 13:19, 20 April 2008 (UTC)