Wikipedia:Reference desk/Archives/Computing/2012 January 25

= January 25 =

Can a JavaScript alert appear when browser is minimised?
I am developing a JavaScript countdown timer. Can I make the timeout alert pop up even when the user is using another application, such as OpenOffice? In my office, the computers have no Internet access and no access to removable media. — Preceding unsigned comment added by 203.116.187.1 (talk) 02:26, 25 January 2012 (UTC)
 * In Internet Exploder? Yes. Chrome? Yes. In Firefox? No, because of security. (tested in latest version of browsers with this example). Javascript isn't the best language for this sort of thing. Von Restorff (talk) 03:00, 25 January 2012 (UTC)

What about for older versions of IE, like IE6? — Preceding unsigned comment added by 203.116.187.1 (talk) 03:47, 25 January 2012 (UTC)


 * In Internet Exploder 6 it works too. Von Restorff (talk) 03:54, 25 January 2012 (UTC)

Or at least make the browser button in the taskbar flash? — Preceding unsigned comment added by 203.116.187.1 (talk) 03:49, 25 January 2012 (UTC)


 * In FF that is not possible, in the other browsers it is not necessary. Von Restorff (talk) 03:57, 25 January 2012 (UTC)

Could I do this with OpenOffice.org Basic? — Preceding unsigned comment added by 203.116.187.1 (talk) 03:49, 25 January 2012 (UTC)


 * Probably. What do you want the program to do, and why? Von Restorff (talk) 03:57, 25 January 2012 (UTC)


 * I'm guessing the OP wants to make some sort of alert show up, but can't use a program designed for that purpose since the computers have no simple way to receive files so it needs to be implemented in situ with whatever is already on the computer. I wonder if some sort of simple default scripting program present on the computers may be a better idea. E.g. VBscript for Windows. It obviously won't be particularly cross platform. Alternatively, just add a scheduled task to say open an PNG saying 'GO HOME NOW' or whatever may work. (In *nix I presume you can implement something in Cron.) Nil Einne (talk) 04:50, 25 January 2012 (UTC)
 * After 48 editconflicts: In OpenOffice Basic the following code makes the button in the taskbar flash:
 * wait 12000
 * msgbox "pizza"
 * Von Restorff (talk) 04:55, 25 January 2012 (UTC)


 * A VBS version: make new textdocument. Rename it to test.vbs. Use the following code:
 * WScript.sleep 12000
 * msgbox "pizza"
 * Von Restorff (talk) 05:15, 25 January 2012 (UTC)

Keyboarding Pro 4, Pro 5, Pro 6 and Keyboading Course 1-25 w/Keyboarding 6
I am a student using Pro 4 when I get to the textbook I do not have a text book. Is Pro 5 or Pro 6 compatabile to use in the place of Pro 4 book? Pro 5, Pro 6 and Course 1-25 the same? My computer 2007. If you need ISBN Number 11142465, 111426465, 0840053320. If there is a different way for a different program including a cd and textbook. Your advie would be appreciated. Thank you very Much — Preceding unsigned comment added by SinderKod (talk • contribs) 03:24, 25 January 2012 (UTC)


 * Just to make sure I understand, you are trying to learn to touch type on a QWERTY keyboard, right ? Is this a US English keyboard (with a dollar sign instead of pounds sterling) ?   StuRat (talk) 18:45, 25 January 2012 (UTC)

SQL query
Hi. How do I perform a query in SQL which selects all items from table A which do not appear in table B? Thanks. --163.202.48.125 (talk) 10:03, 25 January 2012 (UTC)
 * Something like  would do it. AndrewWTaylor (talk) 10:19, 25 January 2012 (UTC)
 * Thanks - I tried that but it takes too long because table B is a list of transactions and table A is also quite big. Is there any way to do the inside query first (i.e. the )? That way it only gets done once. --163.202.48.126 (talk) 10:48, 25 January 2012 (UTC)
 * You could extract the relevant IDs from B into a temporary table, perhaps using  to keep it to a reasonable size. If you need to do the query regularly you could put it in a stored procedure. AndrewWTaylor (talk) 13:35, 25 January 2012 (UTC)
 * Another way is to use "where not exists". There is a difference in the handling of nulls, see e.g. or search the web. Captain Hindsight (talk) 10:44, 25 January 2012 (UTC)


 * Many databases allow you to do this "set difference" operation directly: Set_operations_(SQL). --Sean 16:59, 25 January 2012 (UTC)
 * You might want to try to JOIN both tables and see where table B contains NULL values. Any SQL server will be optimized to do joins. "Where not id in ..." constructions are inherently slow if the server takes it literally, but for example MS SQL seems to be smart enough to understand what you mean and secretly turns your query into a JOIN-operation. Do make sure you have the right indexes on both tables! Joepnl (talk) 23:44, 25 January 2012 (UTC)

Image Processing using Fourier Transforms in MATLAB
Hallo all,

I am stuck in a problem where I have images of a car at various distances and from these I have to estimate the visibility. My approach was to take the Fourier transforms of all images and then filter out the low frequencies leaving only the high frequencies, which correspond to sudden changes in pixel values. Then I made a scatter plot of the mean values of the amplitudes of the Fourier coefficients against distance of the cars to see the general trend.

However the scatter plot is inconclusive. While the amplitudes do attenuate gradually, there are too many outliers. Does anyone know if there is a better metric than mean which could be used to analyze the trend? Thanks in advance! :-) 141.113.85.93 (talk) 10:15, 25 January 2012 (UTC)


 * Can you explain a bit more ? Are you are trying to detect fog, smoke, smog or some other factor which limits visibility ?  More distant objects should appear less colorful, and the edges should also be fuzzier, which implies that either looking for less color variation or using an edge detection method might work.  And one obvious potential problem is the lens on the camera you are using clouding up.  Is it heated to prevent this ? StuRat (talk) 18:34, 25 January 2012 (UTC)

Patent for content downloads
Hi all, someone told me that some person has managed to score a patent for content downloads on iTunes, meaning those in-app purchases you can make, like pay an extra $1 and remove adds etc. Is this true, because it sounds like something that would have been big news? And what is the correct term for content downloads/ in app purchases? I get meaningless hits on google, so I must have the wrong term. Thanks, IBE (talk) 10:55, 25 January 2012 (UTC)
 * 'Content downloads' is confusing since downloading music or apps from iTunes is obviously a content download. And content download is also what some apps do after install and first run (at least on Android). But neither of these seem to be what you're referring to. If you're referring to 'in app purchases' meaning buying stuff inside an app then a simple search for 'in app purchases patent' will find the name Lodsys for you. And plenty of sources discussion the dispute e.g. . It also seems from that search that Apple themselves filed for a patent  in 2010. (Considering I'm pretty sure Facebook games have were doing it before 2010 and free to play MMOs which are particularly common in East Asia before that (i.e. plenty of prior art), I'm not sure how successful they will be. But I guess it will depend on the specifics of their patent and how obvious the jump from what the free to play people were doing, so only time will tell.) Nil Einne (talk) 12:55, 25 January 2012 (UTC)


 * http://www.groklaw.net is arguably the best source of info on the Lodsys case, should you want to hunt for more details. --Tagishsimon (talk) 13:12, 25 January 2012 (UTC)
 * That's "http://", not "http:\\". I've taken the liberty of editing your comment, as confusion between the forward slash and the backslash is a personal pet peeve of mine. J I P  &#124; Talk 21:56, 25 January 2012 (UTC)

Thanks - scary business. I've put it as resolved, but people are free to add more, and I'll be back to check - quite an interesting discovery. IBE (talk) 14:11, 25 January 2012 (UTC)

Is there a way to call a toll free number without them seeing your number that doesn't cost a fortune?
As caller ID blocking has no effect on the ANI (automatic number identification) system toll free number uses, I can't find a way to do it without some calling card or VoiP system that costs something like 20 cents a minute. And the free VoiP stuff that give samples are only 3 minutes which is too short. About 20 years ago I read some text that said there was some way to turn the whole ANI system off for the call but then you'd pay for the long distance call, but that was 20 years ago and I don't remember. Are you ready for IPv6? (talk) 20:49, 25 January 2012 (UTC)
 * I believe you can call 800-numbers for free on Skype. Other than that - Use a payphone. Avic ennasis  @ 23:55, 1 Shevat 5772 / 23:55, 25 January 2012 (UTC)
 * Or, route your call through a different long-distance carrier, using 10-10 codes, or call the operator and have them place the call for you - both of those will also tend to obscure ANI info. (Handy tidbit for testing - MCI, via 1-800-444-4444, will have an automated system playback the ANI number it received.) Avic ennasis @ 07:25, 2 Shevat 5772 / 07:25, 26 January 2012 (UTC)

Brute-force attacks against Gmail passwords
Hi,

According to : "For reasons too complex to explain here, even some systems, like Gmail’s, that don’t allow intruders to make millions of random guesses at a password can still be vulnerable to brute-force attacks." How does this work?

Thanks. Apokrif (talk) 21:42, 25 January 2012 (UTC)


 * For starters they could brute force some other system that uses the same password, or has a copy of the password in plain text. ¦ Reisio (talk) 21:53, 25 January 2012 (UTC)
 * Or by rate-limiting the brute-force password-guess attempts to a rate below the detection threshold; or hopping IPs by using a bot-net. Basically, counter-countermeasures - playing the part of the cat in the cat and mouse game. Nimur (talk) 21:55, 25 January 2012 (UTC)
 * Or use a combination of brute force, but somehow restricted by a dictionary. Just try the passwords like 'mypassword' in thousand of gmail account. I'm sure you'll find somehting. — Preceding unsigned comment added by 88.8.69.246 (talk) 23:10, 25 January 2012 (UTC)
 * This is probably referring to brute forcing many different accounts in parallel from many different machines, by people who just want compromised accounts and don't care whose. Gmail can rate limit logins by source IP or by account, but when both the source IP and account are different each time it's just business as usual. -- BenRG (talk) 01:08, 26 January 2012 (UTC)
 * Combining a botnet with a captcha solver and a good dictionary makes this stuff easy. But I prefer iStealer, much easier. Von Restorff (talk) 01:35, 26 January 2012 (UTC)
 * That program appears to be a user-interface for building semi-customized trojan software. Those types of attacks constitute a totally different class, and are not brute-force attacks.  Trojan programs are also much easier to defend against.  I simply choose not to run untrusted software, and so I am immune by default to the entire category of attacks that "iStealer" makes so easy.  Protecting my computers from distributed brute-force attacks is more difficult.  Nimur (talk) 07:13, 26 January 2012 (UTC)
 * Ever heard of using a binder to make it FUD? If the goal is to get Gmail passwords using iStealer is much easier than using a combination of a botnet with a captcha solver and a good dictionary. If you have a brain the size of a planet you can steal a botnet, if you have some money you can pay for a captcha solving service, and good dictionaries are easy enough to download, but still this is much harder than using iStealer. Protecting from bruteforce attacks is pretty easy actually; I am using Extreme GPU Bruteforcer and it would take a very very long time to crack my own TrueCrypt password. And if you do there is a second layer of encyption. I live too far away, but if we lived in the same house it would cost just 5 dollars to get your passwords. Von Restorff (talk) 08:05, 26 January 2012 (UTC)