Wikipedia:Reference desk/Archives/Computing/2008 September 28

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September 28

U3 Password Enable

Hello. How can I enable password protection on a U3 Launchpad? The Enable Security button is not on the Launchpad nor in the U3 Launchpad Settings. I unsuccessfully searched in the Help files. Thanks in advance. --Mayfare (talk) 02:18, 28 September 2008 (UTC)

Rails question

Somehow I am unable to create a database. Every time I do rake create:db the console gives me rake aborted!/uninitialized constant ActiveRecord. ActiveRecord and rubygems both seem to be fine. I have the latest version of Rails. --hello, i'm a member | talk to me! 02:56, 28 September 2008 (UTC)

PDF to HTML

Hello daer Wikipedians!i want to know about a free software which convert PDF files into HTML.i use it for the Ubuntu Full Circle Magzine ,Please help me.Thank You —Preceding unsigned comment added by 119.154.37.84 (talk) 04:44, 28 September 2008 (UTC)

You should elaborate a bit on what you want out of this. Do you want it to just grab the text out of the PDF, and put it into a text file and then you can stylize it into HTML? This is not hard (but not much better than just copy-paste of the text itself). Do you want to replicate the layout of the PDF as HTML? This is not only very very hard, but unwise -- PDF and HTML use very different graphical devices to render them and different types of layout elements. An exact-translation of a PDF to HTML would not be very good HTML, if it were even possible. HTML is a very different type of layout paradigm than desktop publishing. --98.217.8.46 (talk) 05:22, 28 September 2008 (UTC)

There are many ways. Adobe has an e-mail service for this: http://www.adobe.com/products/acrobat/access_onlinetools.html. You can also use GMail: http://labnol.blogspot.com/2005/12/convert-doc-xls-ppt-rtf-pdf-to-html.html. You could also download a free trial of Acrobat Professional and save the PDF as HTML. None of these methods work very well, though. You'll get the best results if you code the HTML yourself. You could also use pdftk to uncompress the PDF and do a find-and-replace in Notepad to generate the code (e.g., replacing \n with <br/>).--Tree 'uns 5 (talk) 06:52, 28 September 2008 (UTC)

The Gmail option will, most likely, strip your result of all images, which is bad news. However, your formatting [most likely] stays, which is good. Kushal (talk) 10:08, 28 September 2008 (UTC)

It depends on the complexity of the document. If it is just a Word file with a single column then yeah, that works fine, though really no better than just copying and pasting the text with Reader. But if it is a real layout (and has images and columns and variable fonts and sizes and etc) then usually it comes out a real muddle. --98.217.8.46 (talk) 21:55, 28 September 2008 (UTC)

where is winamp's media library database ?

Hi, my winamp's been crashing for sometime due to gen_ml.dll, and I believe that its due to corrupted media library databases. Deleting them might solve the problem as that would force the databases to be reconstructed. But can anybody please tell me where they are located? It used to be main.dat but the latest's version is using some other path. —Preceding unsigned comment added by 117.201.113.34 (talk) 08:24, 28 September 2008 (UTC)

Under WinXP, if you have per-user save enabled, it'll probably be under %appdata%\Winamp, or 'Documents and Settings\user\Local Settings\Application Data\Winamp'

If you're just saving one list, it may be under 'Documents and Settings\All Users\Application Data' or '\Documents and Settings\All Users\Local Settings\Application Data\Winamp'

I'll try to post back the exact location when I get to my home desktop. Washii (talk) 23:07, 29 September 2008 (UTC)

Had to Google it (assuming XP again). Winamp forums says '%appdata%\Winamp\Plugins\ml' (minus single quotes) if you're using per-user stuff. Probably 'Documents and Settings\All Users\Application Data\Winamp\Plugins\ml' for system-wide. Could probably just rename the 'ml' to 'ml.BAD' or something and see what it does. Washii (talk) 03:10, 30 September 2008 (UTC)

two thrones

where can i get a picture or wallpaper that depicts both the princes sitting on two thrones?? —Preceding unsigned comment added by 122.50.128.79 (talk) 09:28, 28 September 2008 (UTC)

Which princes do you have in mind? --- OtherDave (talk) 10:38, 28 September 2008 (UTC)

My guess is that he means William and Harry. --Russoc4 (talk) 17:24, 28 September 2008 (UTC)

In which case the answer would be: you can't. Humanities would be better for this kind of question, hehe. --Cameron* 19:00, 28 September 2008 (UTC)

Why would William and Harry be sitting on thrones? —Tamfang (talk) 20:33, 28 September 2008 (UTC)

You need a country ruled by princes, not kings. Like Monaco. They probably have thrones.81.143.61.181 (talk) 09:20, 30 September 2008 (UTC)

Upgrading Laptop RAM

Hello ref desk. I have a 4 year old Dell Inspiron 9300 and recently bought a new hard drive, upgrading my 40GB to 80GB. I did this because I thought it was going bad, but apparently one of my RAM sticks was bad. I started 4 years ago with 512MB of RAM and upgraded to 1GB of DDR2 533 (PC2 4200) CAS latency 4. This was about 3 years ago. About 1 year ago, I purchased a second 1GB stick, exactly the same item (and 1/3 the price). This stick I purchased a year ago is the one that failed. Now I am concerned that my older stick is going to go at some point, so here's my situation. Should I spend:

1. $17.49 for 1x G.SKILL 1GB 200-Pin DDR2 SO-DIMM DDR2 533 (PC2 4200) with a Cas Latency of 4
2. $36.99 for 2x G.SKILL 1GB 200-Pin DDR2 SO-DIMM DDR2 533 (PC2 4200) with a Cas Latency of 4
3. $34.99 for 2x G.SKILL 1GB 200-Pin DDR2 SO-DIMM DDR2 667 (PC2 5300) with a Cas Latency of 5
4. $44.99 for 2x G.SKILL 1GB 200-Pin DDR2 SO-DIMM DDR2 667 (PC2 5300) with a Cas Latency of 4

Option 1 would just replace my broken RAM with the exact same stick. Option 2 would replace both of them with the exact same sticks. Option 3 would replace both of them and upgrade the speed, but downgrade the Cas latency (whatever that is). Option 4 would upgrade the speed and keep the same Cas latency.

Now, will I really benefit from an upgrade in RAM speed if my processor is rated at 533MHz FSB, with apparently an actual Bus Speed of 133MHz.

Here is my CPU-Z report.

It says the memory frequency is actually 266MHz and the Bus Speed is 133MHz, giving me a RAM ratio of 1:2. Why is my bus speed only 133MHz and why is my RAM ratio not 1:1, as in, 533:533? And what is Cas Latency?

--Russoc4 (talk) 15:07, 28 September 2008 (UTC)

Personally, I would go with option 3, just because it is cheaper and faster (also the top speed supported by your laptop). I'd also go with option 3 because working in equal pairs is generally a good thing. If you want to spend the extra cash, you could go with Option 4, though I highly doubt it would be worth it (though it is just ten bucks).

The Memory frequency is 266MHz because DDR means Double Data Rate. Multiply 266*2 and you get..? 532. You can ignore the bus speed for the most part. That's what most of your other devices run across.

CAS_latency

I've heard G.SKILL is a somewhat good brand. You should probably take a look at warranty they offer with your old stick, as well. If your original stick has lasted this long, it's possible it will last until you ditch that laptop, too. I personally prefer PQi for the lesser brand-names, and they offer a lifetime warranty, though probably slightly more expensive than the G.SKILL. All of PQi's RAM has done extremely well for me, too (I've had 8 sticks of DDR and 2x 15$ 4GB flash drives). Washii (talk) 02:53, 30 September 2008 (UTC)

Also, I just noticed: Crucial says your laptop supports dual-channel memory, which means it will be effectively faster by having matched pairs. Washii (talk) 02:56, 30 September 2008 (UTC)

wifi turns itself off

I am not sure of the terminology so please bear with me. I have a quite battered but newish to me Acer Aspire 3680 laptop, with Windows XP and FireFox. It used to be fine with wifi. Now whenever I reboot, it refuses to recognise any networks. This caused no end of grief and a long wikibreak. Fortunately a nice passing techie (no longer around) showed me a lengthy trick to turn it on again -- I say lengthy, in that I have to remember my way through half a dozen menus. (Start --> My Computer --> Right click --> Manage --> Services and Applications --> Services --> Wireless Zero Configuration --> Start the service.) Is there a way to make the wifi stay on? Thank you. BrainyBabe (talk) 20:36, 28 September 2008 (UTC)

Instead of selecting "Start the service" at the last step, try selecting "Properties," then in the list box marked "Startup type" select "Automatic"—I assume it's currently set to "Manual." Then click okay. You may have to start the service one last time, but hopefully it will start automatically the next time you reboot. By the way, instead of Start --> My Computer --> Right click --> Manage --> Services and Applications --> Services, you can press Win+R, then type services.msc, then press Enter. -- BenRG (talk) 22:22, 28 September 2008 (UTC)

I use a set of batch scripts on my Desktop to turn off Wireless Zero Config, since it gripes at me when I use the hardware off switch for the radios.

To turn off, use the line 'net stop "wireless zero configuration"' (minus the single quotes)

To turn on, use the line 'net start "wireless zero configuration"'

(For anybody that cares, I set '@echo off' at the beginning of both scripts)

And sorry to whomever I just wiki-conflicted with! Washii (talk) 23:14, 29 September 2008 (UTC)

cookbook curve fit

I need something from a Numerical Methods book that I gave away twenty years ago! Given a set of points $x_{i},y_{i}$, what's a compact expression for the polynomial (of minimal degree) that fits exactly? —Tamfang (talk) 20:36, 28 September 2008 (UTC)

$\sum _{i}y_{i}\prod _{j\neq i}{\frac {x-x_{j}}{x_{i}-x_{j}}}$? -- BenRG (talk) 21:23, 28 September 2008 (UTC)

That's the one, thanks. —Tamfang (talk) 21:49, 28 September 2008 (UTC)

Here's how to remember it so you'll never have to look it up again: by linearity the polynomial you want is the sum of $y_{i}$ times a polynomial that's 1 at $x_{i}$ and zero at the other points. To be zero at the other points it must have factors of $(x-x_{j})$ for every $j\neq i$, i.e. it must be a multiple of $\prod _{j\neq i}(x-x_{j})\,$. To make that equal one at $x_{i}$ you divide by the result of plugging $x_{i}$ into it, that is, $\prod _{j\neq i}(x_{i}-x_{j})\,$. -- BenRG (talk) 22:33, 28 September 2008 (UTC)

By the way, that formula is called the Lagrange polynomial (could someone make a redirect from Lagrange interpolation polynomial which is a more usual name for it?) and there is more info about the formula at that article. 75.62.6.87 (talk) 09:30, 16 March 2009 (UTC)

firefox/php/require statment

i've got a problem at the moment that i'm developing a web page and recently played around with the include/require statments loading up class documents, i decieded to go back to what i and before (not a backup just what i rememebred i had before)now all i get when i load the page is firefox saying

Redirect Loop Redirection limit for this URL exceeded. Unable to load the requested page. This may be caused by cookies that are blocked. The browser has stopped trying to retrieve the requested item. The site is redirecting the request in a way that will never complete. * Have you disabled or blocked cookies required by this site?

* NOTE: If accepting the site's cookies does not resolve the problem, it is probably a server configuration

issue and not your computer.

i cleared my cookies and cache with no effect, and hadnt done anythign with my cookies for ages

now when i comment out the require_once statment on my index page it works (untill it has problems with the class's no longer existing but thats a different problem)

a little about my code: index.php loads up session.php (my primary class document, session page handles all user log in/mangment stuff) which session then loads up other classes (database/process/error handling), all pages have require_once and it worked fine before i started tinkering with it

any suggestions to whats happening?--82.16.140.152 (talk) 20:42, 28 September 2008 (UTC)

Search your code for a header command that is redirecting the page. Wherever you find it, that is being called over and over. Why? It is not possible to say without seeing the code. -- kainaw™ 20:48, 28 September 2008 (UTC)

Somewhere you've got your client side stuff putting out HTTP headers in a way that has started a constant loop. Where? Can't say—you've got to find out by looking very closely at your code. Most likely one of your files is then for some reason calling another which calls the first one again. --98.217.8.46 (talk) 21:47, 28 September 2008 (UTC)

doesnt require_once handle that problem?--82.16.140.152 (talk) 22:38, 28 September 2008 (UTC)

guess not just fixed it--82.16.140.152 (talk) 22:39, 28 September 2008 (UTC)

Maybe maybe not. But relying on something like that for this purpose is very, very bad form. This is a serious problem in programming logic. --98.217.8.46 (talk) 22:43, 28 September 2008 (UTC)

Require_once will only include a script once, but it will not keep you from calling a function in that script many times. A very common mistake is the logic: "Redirect to a cookie setter page to set cookie FOO. Then, if cookie FOO is not set, redirect to the cookie setter page." If cookies are turned off, this will repeatedly redirect. I personally don't get why so many people do this. If you failed to set the cookie the first time, why try it again? -- kainaw™ 11:08, 29 September 2008 (UTC)

Hardware Java

Would be possible to build a hardware emulator of a Java VM? —Preceding unsigned comment added by 62.49.27.114 (talk) 23:16, 28 September 2008 (UTC)

Yes. The Java VM is a computer program. Any and every computer program can be implemented with just hardware - but it will usually be much (MUCH) larger than a standard computer. For example, I worked on Litton Industry radars that implemented a simple vector graphics display using hardware. It was, from memory, about 200 4 foot by 3 foot circuit boards packed full of components. An equivalent program would probably be a couple thousand lines of code and fit nicely on a floppy disk. -- kainaw™ 03:24, 29 September 2008 (UTC)

It's been done many times, from quite early on; see Java processor. --Sean 12:32, 29 September 2008 (UTC)

Kinda. Those implement only a subset of the bytecodes in hardware (logic, flow, arithmetic, fp, redir, sync) and a further subset in microcode (stack management, some support for gc), with a few of the most complex things written in software (ref:picoJava I datasheet, 1997). Quite a lot of what you'd formally call a "Java VM" (heap, gc, classloader, verifier) all has to be written in software. Kainaw is correct that someone could implement all that in gates, but it'd be bonkers to do so (and I'd pity anyone who had to implement a verifier in verilog). -- Finlay McWalter | Talk 12:55, 29 September 2008 (UTC)