Wikipedia:Reference desk/Archives/Computing/2009 January 30

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January 30

Gamma Thingy

If I display a png or bitmap which has a sequence of shades in linear progression (say 0, 64, 128, 192, 255) will I see a linear sequence of intensities, from completely dark to completely light, or is there some kind of distortion? Black Carrot (talk) 00:16, 30 January 2009 (UTC)

That is a surprisingly tricky question. The naive answer is yes - in the case you describe, you'll see a set of stripes. If you went 0,1,2,3,4,5,....253,254,255 then it would be a smooth gradation. Now - linearity: Tricky. There is a phenomenon called "Gamma correction". The monitor on your display probably doesn't naturally produce equal numbers of photons for equal steps of brightness. CRT monitors are particularly bad - but all display technologies have SOME kind of non-linearity. Computer software has to compensate for that - either by drawing un-equal steps of brightness for equal steps across the screen - or by using a hardware feature of most graphics cards that adjusts this non-linearity as the data is turned into an analog signal to send to the monitor. If you have a pure-digital system, the monitor may take account of that. No two monitors have the exact same gamma - and gamma may change over the life of the machine as it wears out and the phosphor coatings fade or outgassing affects your plasma or the xenon bulb in your video projector gets old...or whatever.

Now - here comes the ugly part. Back in the early days, those bozo's at Microsoft didn't pay any attention to this - the display would show the data 'raw' - non-linearities and all. UNIX/Linux/MacOS all had gamma correction from the get-go...but not Windows. So what happened was that each individual program had colors that were hand tweaked 'by eye' by individual programmers. That history continues even now that Microsoft finally woke up and put the feature in there. The trouble NOW is that if you set the gamma so it's mathematically correct and you have pure linearity - some programs look terrible. It's a mess basically.

SteveBaker (talk) 00:39, 30 January 2009 (UTC)

Crazy. If I produce a png or bitmap myself, though (using java ImageIO) and a gradient is linear, does that mean that on most modern monitors, in most modern versions of Windows, the gradation of intensities will appear almost linear to the extent our eyes can distinguish? I ask because I'd like to render things like solid balls, but I'm not sure whether I can simply set each pixel in the file to the intensity I want to see, and let the OS and hardware handle it, or whether I have to make things like gamma corrections manually as I render it. Black Carrot (talk) 17:44, 1 February 2009 (UTC)

RAM won't work

I tried to upgrade the ram in my dell dimension 3000 from 512mb to 2gb. I went to microcenter and they assured me it was the right ram. I tried to put it in and all I got was six beeps and no screen. I tried putting the old RAM in and it still won't work. I lined up the little hole in the bottom with the slots, and pushed the clips back in, but nothing. Is it possible my attempting to fit the ram in, I could have scratched it so bad, that neither set will work, or am I doing something wrong? Also- before I put the ram in, I cleaned out some dust. Could that be a factor, although the ABCD buttons on the back indicate it's just a memory issue?97.118.230.106 (talk) 01:04, 30 January 2009 (UTC)

It can take significant force to get the memory modules seated properly. You need to apply steady pressure on both ends of the chip, but you should not have to push hard enough to flex the motherboard (which can cause internal damage). When properly inserted, the plastic clips will automatically latch the memory module. Each of the 1GB DIMMs can be tried separately (likely in either slot). Try to narrow the problem down to a specific module or a specific slot. – 74  02:20, 30 January 2009 (UTC)

I have replaced a lot of RAM in my day and even I got totally perplexed by some RAM that appeared to be dead-on-arrival but ended up just needing more force in putting it in the machine than I had expected (it was not a model of laptop I had used before). Try it again. Slowly but very firmly keep pushing the RAM in. It should be VERY snug. --98.217.14.211 (talk) 02:25, 30 January 2009 (UTC)

Thank you! I pushed in my new RAM and it works fine!97.118.230.106 (talk) 02:44, 30 January 2009 (UTC)

Online money

Resolved

Is there any way to do anonymous online payments? I know there is something like paypal, but not all sites accept that. (Of course I do not want something like stolen credit cards and stuff like that...) 87.196.76.214 (talk) 01:37, 30 January 2009 (UTC)

A reasonably "anonymous" approach to online payments is to buy a prepaid credit card (often sold as "gift cards" in stores/malls; look for one with a major credit stamp). Pretty much anywhere online will accept it as a credit card. – 74  02:05, 30 January 2009 (UTC)

eCache 121.72.165.189 (talk) 11:20, 31 January 2009 (UTC)

There's something concerning about an anonymous bank (not an anonymous account at a named bank). If they decide to abscond with all the deposits tomorrow how do you find/prove who has your money? – 74  21:46, 31 January 2009 (UTC)

Thanks, I will check out the prepaid credit card.

Signal handler typedef

does anyone know more about these two statements

typedef void (*f)(int) .......statement1 (was declared outside the main() )

signal(SIGFPE,(f)SIG_IGN) ......statement 2 (was declared inside the main() )

the above two statements help me to ignore any kind of mathematical error

but i don't know what the words exactly stand for

can anyone help me ?

please....

I put a title to your question so people might notice it better. The first line (type-)defines f as a pointer to function that returns void and takes one int parameter, google for function pointers if you want to know more. On the second line (f)SIG_IGN casts SIG_IGN to be of type f. --194.197.235.61 (talk) 09:07, 30 January 2009 (UTC)

Also see here if you don't know what signal, SIGFPE, SIG_IGN are doing. --194.197.235.61 (talk) 09:12, 30 January 2009 (UTC)

When you get certain types of math error (like taking the square root of -1 or dividing by zero), the floating point hardware generates a "signal" - an "interrupt" that causes the CPU to execute a "signal handler" - which is a piece of software that reports the error up to higher levels and causes your software to fail (as indeed it should if you are being 'naughty' like that!). The 'signal' function call lets you replace one signal handler with another - which could be your own function that prints "naughty, naughty!" and then carries on working. However, it's very common to want to "do nothing" for a particular kind of signal - and the operating system therefore provides a "do nothing" function called 'SIG_IGN' that IGNores a SIGnal. OK - so the second line could read:

signal ( SIGFPE, SIG_IGN ) ;

Meaning "replace the SIGFPE signal handler with the signal-ignore function". SIGFPE is the name of the SIGnal for Floating Point Errors. The trouble appears to be that the definition of the 'signal' function isn't compatible with the definition of SIG_FPE for some bizarre reason. I've noted myself that the definition of the 'signal' function has changed a lot over the years and doesn't always make a whole lot of sense. (I even started collecting them at one time: [1]!!!) It looks like someone is trying to patch around an incorrect definition of either 'signal()' or 'SIG_IGN'...which really shouldn't be necessary. So the first line defines a 'typedef' that maps the correct data type for 'pointer to signal handler' to the name "f" (YIKES!!!! What a crappy choice! Please club the author of that line to death with a blunt instrument so I never have to read another line of his/her code!). The second line then does a 'cast' to convert the type of the SIG_IGN function to be of type "f" so you don't get a complaint from the compiler. That messing around shouldn't be necessary in a correctly set up system of header files.

SteveBaker (talk) 13:02, 30 January 2009 (UTC)

Screensaver setup help

Im trying to install a screensaver. it is an executable file. when i try to start the installer, it says "Unable to register Shockwave Flash ActiveX control. Please close all other applications and try again." Now, ive tried closing everything else, but still get the same message. what can i do? 71.223.237.170 (talk) 06:28, 30 January 2009 (UTC)

try visiting the macromedia/shockwave website and make sure you have the correct/most current version firstly and then try the screensaver. However if the message keeps appearing it may be a corrupt file.--CorrectlyContentious 16:38, 30 January 2009 (UTC)

Macrovsion - How TVs are able to play and VCRs not?

Why the AGC and color stripe modifications used in Macrovision, prevent recording and playback with a VCR, but don't interfere with AGC or color burst of a TV system? —Preceding unsigned comment added by Krisfriend (talk • contribs) 10:37, 30 January 2009 (UTC)

According to our Macrovision article (as best as I can understand it), they take advantage of the limited dynamic range of VCR's - that is to say their inability to display very bright and very dark signals. To prevent that from being a problem the VCR examines the average brightness and contrast of the input signal and either boosts or limits the amount of brightness adjustment it does to it before writing it to the tape. This "automatic gain control" is then tricked by Macrovision into thinking that a very bright picture is being displayed when it's really not...which causes the VCR to 'turn down the brightness' to an extreme degree when recording - and turn it way up when replaying...which produces a very noisy - even unwatchable - video. How they do that is to inject a very, very bright signal into the scanlines of the image that are off the edge of the screen for most TV's. This pushes the 'average brightness' calculation inside the VCR way up - and disrupts the recording process. I would guess that this doesn't upset TV's because they don't look at the entire screen to do AGC - but do it more line-by-line. But as our article points out - not all TV's ARE unaffected. Some are screwed up by the Macrovision system.

Hopefully, the death of the VCR and birth of the recordable DVD (which won't suffer from THIS problem) will also be the death of the accursed Macrovision artifacts.

SteveBaker (talk) 12:50, 30 January 2009 (UTC)

Actually, DVD recorders/players are backwards compatible (or would that be backwards incompatible) with Macrovision signals. Upon receiving a Macrovision signal DVD recorders are supposed to stop recording, and DVD players are supposed to add Macrovision signals to any played content that is marked as 'copyrighted'. It looks like we will be saddled with this ugly signal hack for the foreseeable future. – 74  13:17, 30 January 2009 (UTC)

That is certainly true of the DVD player and DVD recorder I have here in the UK. I tried copying a commercial DVD and the recorder only displayed a message saying "Copyrighted content". Astronaut (talk) 01:12, 31 January 2009 (UTC)

css uploading

I have been teaching myself html and now css.Have been able to make a working css website in browser with external style sheet.I have uploaded index html with a link to the external style sheet but nothing happens when viewed on the web except that the background image appears and repeats itself as specified in the style sheet. I have gone over the links from each page to the external css and they appear correct. Any idea where I should look for the problem.I use a Mac. Any advice appreciated.91.125.144.22 (talk) 17:53, 30 January 2009 (UTC)

Is a specific URL available? - Jarry1250 ^{(t, c)} 18:46, 30 January 2009 (UTC)

Try the W3C Validation Service on your css.Dmcq (talk) 19:26, 30 January 2009 (UTC)

Does it work locally on your computer? If it works locally but not remotely it may have to do with how your server is set up or how you have specified the external link. --140.247.242.36 (talk) 20:43, 30 January 2009 (UTC)

Sibelius music software and Kontakt Player

I'm using Sibelius 5.0 and the Kontakt Player libraries/function etc that come with it. I'm wondering if there is a way to import my own samples from elsewhere so that they can be used in Sibelius and in audio exporting.

Thanks, --86.3.86.123 (talk) 19:00, 30 January 2009 (UTC)

The Sibelius Help Center is the best place for this sort of question, especially the "chat page", where you will find a lot of knowledgeable users as well as some Sibelius staff. AndrewWTaylor (talk) 15:05, 31 January 2009 (UTC)

RLE files

What program should I use to view RLE files? Lucas Brown 42 (talk) 20:05, 30 January 2009 (UTC)

IrfranView? --wj32 ^t/c 21:20, 30 January 2009 (UTC)

Check a file extension library site - here is one [2] - this will tell you all the programs that have used the extension. Exxolon (talk) 01:06, 31 January 2009 (UTC)

A RLE file could be a run-length encoded bitmap (BMP) file. Try to rename it <file>.bmp and open it in any bitmap editor (e.g. Microsoft Paint). --Andreas Rejbrand (talk) 14:37, 31 January 2009 (UTC)

Spellcheck has Wrong Language

The spellcheck in my Outlook Express, which comes from my Microsoft Office Word, is French and I can't change it to English. If I do a spellcheck I have to add every other word, which doesn't tell me if it's right or wrong in English. I can't find out what the spellcheck dictionary in my Word is. Please help. —Preceding unsigned comment added by 74.225.125.182 (talk) 20:12, 30 January 2009 (UTC)

If you open Microsoft Word, you'll see, at the top of the screen, a series of tabs, one of which is Tools. Click that, then click Language from the drop-down menu. This should produce a pop-out list from which you can click Set Language. According to the legend on the box which appears, the spelling and proofing tools automatically use the dictionary from the selected language. Just click whichever language you wish from the box and close everything again. Pavel (talk) 20:37, 30 January 2009 (UTC)

What you are seeing is a "feature" of upgrading to Office 2007 - see this Knowledge Base article. Outlook Express uses the Office spell-check dictionaries but Office 2007 made some changes to the format of the spell-check dictionaries (except for the French dictionary) which made them incompatible with Outlook Express. Unfortunately, Micro$oft didn't think necessary to patch Outlook Express because everyone will soon be upgrading to Vista and Windows Mail - the Outlook Express replacement in Vista. So what to do? Microsoft's solution - use an external spell-check is a hopeless suggestion. Instead, I suggest migrating your mail to Outlook 2007 or download a non-Microsoft mail program like Thunderbird. Astronaut (talk) 01:07, 31 January 2009 (UTC)

Thank you Pavel and Astronaut for your quick replies. 1) My "Word" doesn't have a tools tab but I did Start>Programs>Microsoft Office>Tools>Language Settings and found I was in English(US). 2)I went to the "Knowledge Base Article" and wrote them a note saying they should create an English Dictionary spellchecker just for Outlook Express because Vista and Windows Mail stink. I have tried other non-Microsoft external spellcheckers and I agree that they are hopeless, and I don't want to migrate to Outlook 2007 or a non-Microsoft mail program and loose all the benefits of Outlook Express, so I see that it is hopeless. Thanks for trying both of you. —Preceding unsigned comment added by 74.225.125.182 (talk) 17:29, 31 January 2009 (UTC) P>S> Thank you Astronaut for clueing me in to http://support.microsoft.com/. I bookmarked it and recommend it to everyone. —Preceding unsigned comment added by 74.225.125.182 (talk) 17:43, 31 January 2009 (UTC)

Outlook 2007 is not too bad and is certainly superior to both Outlook Express and Windows Mail. Outlook 2007 can easily be configured to work with your mail provider and you don't need a huge Exchange Server to make it work well. I really don't see what "benefits" there are in sticking with Outlook Express, that cannot be found in Outlook 2007 or many other mal programs. Astronaut (talk) 08:57, 2 February 2009 (UTC)

Vista

My machine crashed a few days ago. Is it okay to get a PC w/ Vista, or should I still run (not walk) to XP? Clarityfiend (talk) 20:17, 30 January 2009 (UTC)

If I were buying a high-spec computer, I'd still want to run XP instead of Vista. I see no virtue in continually changing operating systems, once you've got a good one. Pavel (talk) 20:28, 30 January 2009 (UTC)

These 1 2 3 4 5 reviews for Vista should help you, plus these 1 2 3 4 5 for Windows 7 if you're interested in upgrading to Vista's successor. --Crackthewhip775 (talk) 21:47, 30 January 2009 (UTC)

Just don't buy a "Windows 7 Capable" computer. – 74  22:18, 30 January 2009 (UTC)

I'm generally a Linux nut, but if you are purchasing a new computer that's not totally low-end, Vista is a fine operating system. IMHO it's much nicer than XP. There's a lot of Vista FUD out there (one can only imagine it's divine justice against Microsoft), but if you do get it on new hardware, it will almost certainly work perfectly for you. I know people like their XP, but come on people, it's time to move on. Belisarius (talk) 23:33, 30 January 2009 (UTC)

In my opinion (which is no more qualified than your own) there are few if any compelling reasons to choose Vista, and a number of compelling reasons not to. The somewhat ridiculous hardware requirements ensure that a "good" Vista experience likely translates to an "great" experience on XP, and several of the new "features" are antifeatures (Protected Media Path, User Account Control, Windows Genuine Advantage). – 74  00:15, 31 January 2009 (UTC)

I'd just repair the computer you have. If it's too slow, buy faster parts for it, but don't buy one with Vista. A computer with Vista may not even be able to handle XP due to driver issues. Plus, no matter what type of hardware you buy, it'll always be a little slow if it uses Vista. I run a computer-repair business, so trust me when I say that Vista is not immune to viruses. In fact, they're very common. Users just click OK when they get the extra confirmation dialog in Vista. If you have to buy a PC with Vista, though, be sure to get Vista Business or Vista Ultimate -- not Home Premium! Home Premium is a pain in the ass to troubleshoot due to the lack of administrative tools.--K;;m5m k;;m5m (talk) 00:25, 31 January 2009 (UTC)

I would definitely buy a good Windows Vista computer, and upgrade to Windows 7 as soon as possible. --Andreas Rejbrand (talk) 00:26, 31 January 2009 (UTC)

Vista has some pretty horrible compatibility issues with older software - I'd strongly recommend XP instead, it's by far the most stable and usable of all the Windows variants I've used. Exxolon (talk) 01:05, 31 January 2009 (UTC)

Which issues? The only compatibility issues I've had are with Windows 3.1 apps, and that's merely because I'm using x64 Vista; it would be the same with x64 XP. -- Consumed Crustacean (talk) 02:33, 31 January 2009 (UTC)

I've had some issues with Visual Studio 2005, SkinStudio, and the ZoneAlarm firewall. I'm working on a computer right now that's blue-screening whenever it tries to connect via dial-up to AOL. I think that's also a software issue since her modem works otherwise. (I don't ask why she uses AOL because that's not my job.) Some other legacy programs don't run elevated by default, but that's fixed easily. The biggest problems, of course, are related to drivers. I've had more than a few issues with that on Vista.--K;;m5m k;;m5m (talk) 03:22, 31 January 2009 (UTC)

On ZoneAlarm and the like, remember that they're mostly snake-oil. If you're going to use Windows, skip XP and go for Windows 2000: it's faster (if not quite so pretty), it does all you need, and there's none of that "product activation" nonsense. (Of course I mustn't recommend GNU/Linux, because your computer has broken down and there's a rule here that Windows users whose computers have broken down mustn't be nudged toward Linux. There's also another one: "If a questioner's Windows computer ain't broke, don't explain how to fix it with Linux.") This message typed on my sole surviving Windows computer, contentedly running Windows 2000. -- Hoary (talk) 03:48, 31 January 2009 (UTC)

Where are these "rules" located? ;)--Xp54321 ^{(Hello! • Contribs)} 03:53, 31 January 2009 (UTC)

I think it's just common sense. I would never tell a customer, "Just format your hard drive and install Linux." One guy at the tech. support desk at my old school told me that and I felt like punching him in the face. I couldn't start my computer and he wanted to have an argument about how Linux was so much better than Windows and how stupid I was for actually wanting to get something done on my computer. In fact, I never tell customers to switch operating systems at all. Fixing a computer generally takes me a couple of hours or so. Installing Linux would take me at least 8. They'd ask, "Can I still use Roxio? Can I still use AOL? Can I still use MSN Explorer? Can I still use my scanner?" And I'd have to say no a bunch of times. As for Windows 2000, as I mentioned above, a lot of these computers won't even run Windows XP because the SATA HDD drivers aren't included on the XP (or 2000) installation disk.--K;;m5m k;;m5m (talk) 04:09, 31 January 2009 (UTC)

They seem to locate themselves on the rare occasion when I've as much as suggested the possibility of Linux in response to a question, any question, here. (What such a suggestion has to do with wanting to start an punch-in-face-worthy argument eludes me.) -- Hoary (talk) 05:10, 31 January 2009 (UTC)

"Switch to Linux" answers are almost always useless. If a (potential) poster already uses Linux, it's very unlikely that they would be asking their OS-question here in the first place. If they don't use Linux, they probably don't want to or know how. By "use" I mean "have used for a while". --wj32 ^t/c 05:37, 31 January 2009 (UTC)

I'll keep the indentation going because it's neat. Zonealarm? AOL? It's not a surprise that poorly written software breaks when the kernel changes. Windowblinds works fine in Vista, and Skinstudio by extension should as well; they even advertise it as such on their site. It does do strange things to the OS though, so YMMV. As for 2K and XP, I would always recommend XP. It's nicer to use, and adds other things. The product activation may be a concern, but there are, uh, ways around it. -- Consumed Crustacean (talk) 05:47, 31 January 2009 (UTC)

Wj32 sez: "Switch to Linux" answers are almost always useless. Hmm. See my thoughts at (or shout me down at, or conceivably even agree with me at) "'Switch to Linux' answers". -- Hoary (talk) 10:45, 31 January 2009 (UTC)

Much as I would like to switch to Linux, I don't think Pokerstars would be overly pleased. Thanks everyone. Clarityfiend (talk) 19:00, 31 January 2009 (UTC)

Building a computer diagnostic and repair utility

For this question we will assume that all computers support booting from USB.

I am trying to build a diagnostic tool that I would use in the event that a windows computer becomes overwhelmed with viruses and spy-ware, or, in the event that windows it self becomes corrupt. The way that i have decided to go about this is to make a boot able usb hdd. This 30g hdd has three partitions; a 10g partition for Ubuntu8, a 1g partition for Ubuntu's swap, and the remaining is a fat32 partition that contains instalation files for AVG, ad-aware, Spybot, HijackThis, and other windows based tools. on Ubuntu I have installed ClamAV as an antivirus. My goal is to be able to find, repair and remove any viruses / spy-ware on a windows partition from my bootable usb hdd using linux based programs. This leads right in to my question; What programs could I use to do the following:

Detect and repair corrupted Mast boot records for a Windows hard drive.

Detect and remove any viruses that are on a Windows hard drive

Detect and repair corrupt operation system files for a Windows computer

Detect and remove spy-ware that are on a Windows hard drive

Edit a window's registry

All from within Ubuntu

I am not that familiar with Unix based operating systems, I would greatly enjoy a program or programs that can do what I want that has a nice GUI, but i am not opposed to using a command line based program. So far I have booted this hdd on 5 uniquely different computers with great success. One of these computers i have filled up with viruses and spy-ware, I will be using this one as a test subject. E smith2000 (talk) 23:57, 30 January 2009 (UTC)

Sounds like a very interesting project - please keep me posted. How do you get an ISO or bootable part onto the thumb drive? — Ched (talk) 04:22, 31 January 2009 (UTC)

I did it by removing the hdd from my labtop and plugging in my usb hdd. I have tried it with XP and it keeps giving me the blue screen of death when it tried to load up the usb drivers. E smith2000 (talk) 06:02, 31 January 2009 (UTC)

You could repair the mbr and missing system files by using a Windows CD. 121.72.165.189 (talk) 11:16, 31 January 2009 (UTC)

Well yes, I could. But my aim here is not to just fix the problems, I am also trying to learn about the different programs out there that technicians use to repair computers. To try and expand my knowledge and learn. That is why I want to construct this. But your comment did give me an idea, I could have an ISO of a windows installation disk, by mounting that, along with the hard drive that I wish to repair from within a virtual PC running from within Ubuntu. Thank you. E smith2000 (talk) 21:06, 31 January 2009 (UTC)

Update, i have installed Virtual Box, allowing me to load up the host's computer's OS as a guest operating system, This will allow me to remove files from Ubuntu that are being used by programs in the host computer. (like viruses) – Elliott  17:24, 2 February 2009 (UTC)