Wikipedia:Reference desk/Archives/Computing/2011 January 17

= January 17 =

android tablets
I notice there are a zillion cheap android tablets sprouting up everywhere, whose hardware looks rather nice. They mostly run Android 2.1 and have vendor-customized UI's and applications, which I presume is like the usual dreck situation from the PC world. Is it likely to be a big problem to root the device and upgrade to a newer version of android, i.e. do they tend to depend on proprietary device drivers and that sort of thing? I'm not trying to plug a particular vendor but one device I'm looking at is here. There are also a lot of even more generic ones at the usual no-name schlock shops. Any thoughts? 67.122.209.190 (talk) 09:58, 17 January 2011 (UTC)
 * Wikipedia has an article about Android (operating system). The main concern for a potential customer will be whether the tablet vendor will be still around during the life of the product and we cannot predict that. Cuddlyable3 (talk) 11:45, 17 January 2011 (UTC)

Given the zillionness, surely one or two come without root disabled. ¦ Reisio (talk) 15:13, 17 January 2011 (UTC)


 * Well, rooting (android-speak for what iphone users call "jailbreaking") generally is not something that vendors intentionally "enable". It's a question of how thorough a job they do preventing it.  Rooting per se is usually not too difficult.  What I was wondering was about the difficulty of installing new versions of android completely from scratch. 67.122.209.190 (talk) 18:00, 17 January 2011 (UTC)


 * I was semi helping someone look in to Android phones once. What I gathered was that porting a new version of Android is generally quite difficult because many/most? vendors don't release the code for their drivers. In particular, most user lead ports we came across didn't seem to get very far. More common appears to be unofficial beta releases of official lead ports. These were with relatively cheap devices and as I said with phones, so YMMV Nil Einne (talk) 20:59, 18 January 2011 (UTC)

Old laptops
In an above thread someone said "It is pretty easy to scrounge old laptops these days." I was going to reply in that thread, but I didn't want to distract from the OPs question. So, is it really that easy? Where do I need to go to find old laptops for free or really cheep? And how old are we talking, Windows 95/XP? 82.44.55.25 (talk) 10:54, 17 January 2011 (UTC)


 * Organizations have what is known as a replacement cycle. For laptops it is between 3 and 5 years. Different organizations have different disposal policies. Example You just need to ask about. A scratch-each-others-back arrangement often works -you just have to find out who's back needs scratching. Knowing how to wipe the drives might get you an intro into a little company who does not want their customer and banking details  ending up in Nigeria nor China.Offer to run DBAN on it to wipe the data, and then upgrade it by installing  a Linux distribution on it.--Aspro (talk) 11:19, 17 January 2011 (UTC)
 * The OP is located in UK where there are many small shops that sell and repair PCs. They are likely to have many old laptops that customers have had replaced or hoped (probably in vain) to trade in, and which are now virtually unsaleable. Ask around. Cuddlyable3 (talk) 11:34, 17 January 2011 (UTC)
 * Try eBay, especially searching for the area near yourself to avoid paying postal charges. Old computers are quite often given away on Freecycle or Freegle, but I've never seen any laptops and there are a lot of people keen to have them. If you think the operating system is too old then you can always replace it for free by one of the many Linux operating systems. 92.15.8.13 (talk) 13:37, 17 January 2011 (UTC)

It's also much simpler to "scrounge" up brand spanking new laptops these days, as they are significantly cheaper. You can get netbooks with everything but an optical drive for $100 (€75, though realistically probably also €100). ¦ Reisio (talk) 15:18, 17 January 2011 (UTC)

For buying cheap old laptops from strangers with actual money, try craigslist.org if you're in a reasonable sized city (they have several sites in the UK). It's basically a classified ad service for local buyers and sellers, so you get to examine the merchandise and buy it in person (avoids some scams, and avoids expensive shipping for heavy objects like laptops). But it's often possible to scrounge them for free or for some informal barter, as people are always upgrading laptops, or these days replacing them with smartphones. 67.122.209.190 (talk) 17:57, 17 January 2011 (UTC)


 * I am fortunate to know someone who runs their own consultancy business and regularly replaces their laptop. I am also know within my family as the person to come to with computer problems.  Therefore it was no surprise I was given 3 old laptops only last year:
 * The oldest was a small Sony Vaio from around 2000 with 20GB drive, 128MB of memory, and a docking station containing a DVD drive, various ports and a wireless internet PC card. Windows XP and Microsoft Office were installed, but the battery was worn out and the screen hinge was damaged (but easily repairable).  I reinstalled Windows using my Windows XP OEM disk and re-authenticated it over the phone.  It now works well for light websurfing and using Office, but really needs more memory (a £25 upgrade).
 * The second was a 15" Toshiba A10 from around 2003 with a 30GB drive and 256MB of memory. Windows XP and Microsoft Office were installed, but the hard drive was dying.  The battery was also worn out and the keyboard had a couple of dead keys.  I upgraded the memory and replaced the hard drive with spares (from yet another dead laptop I was given a year earlier) and reinstalled and re-authenticated Windows, though I was unable to save the Office installation.  I can get a new keyboard on eBay for about £15 though a new battery is harder to find.
 * The last was a HP machine from around 2006 with a 40GB drive and 256MB of memory. Again Windows XP and Microsoft Office were installed, but the previous owner had completely trashed the installation by attempting to upgrade to Vista.  Unfortunately, the battery is the worst of the three but can easily be replaced for about £50.  Other than that, it is a good and quite fast machine.  I could have reinstalled Windows, but instead chose to install Linux for another project.
 * Yes, old laptops are quite easy to obtain, particularly if you have contacts, but you have to be prepared to put up with a number of issues and recognise the machine's inherent limitations (slower CPU, not the latest screen technology, no built-in wifi, etc.) You should also be comfortable with replacing parts, canibalizing other broken laptops for parts and/or spending a little to fix something.  Astronaut (talk) 22:01, 17 January 2011 (UTC)
 * I'm curious about you saying "I reinstalled Windows using my Windows XP OEM disk and re-authenticated it over the phone". Was that the disk that came with the Sony Vaio you were given, or was it some other computer's disk? If the later, how did you get through the asuthentification process exactly? I would have expected problems in those circumstances.


 * If the OP wants to tinker with second-hand computers, then I'd recommend doing it with towers or desktops rather than laptops. The parts for the former are much easier to get and to fit, as they are largely interchangeable, while I understand that laptop parts are brand-specific. When I've renovated an old computer, the only difficult thing is working out what particular memory to order to give it the most possible memory. If you replace the old operating system by a free new one, which is easy to do if you can burn a CD, then you do not have to fiddle with updating the drivers or removing the clutter of the previous user. I think upgrading the BIOS is best done in Windows though. 92.28.254.64 (talk) 23:52, 17 January 2011 (UTC)


 * When you buy a new laptop, it usually comes with Windows preinstalled and a Certificate of Authenticity (CoA) stuck on the bottom. If you are lucky you also get a Windows installation disk, but increasingly common is a means to burn your own installation disk (something you are encouraged to do early in your ownership).  That is a normal OEM disk, but it is usually tied to a specific PC manufacturer and (supposedly) cannot be used to fix a different manufacturer's PC.  Microsoft also supplies two other types of Windows installation disks: retail disks that you buy in a shop; and generic OEM disks that are supplied to smaller PC makers.  These generic OEM disks are distinguished by a large hologram on one side and are not tied to a particular manufacturer.  The physical disks themselves are almost worthless without the all important CoA.  PC manufacturers buy CoAs and stick one to each PC they preinstall Windows on.
 * Because all the old laptops had no installation disks but did have valid CoAs stuck to their bottoms, I was able to pursuade my local PC parts & repair shop to sell me a copy of their generic OEM installation disk for the cost of the media and their time (ie. £5!), something that almost certainly won't work with a large retail store like PC World. So, while my Windows XP OEM disk doesn't have a large hologram on it, it is a copy of one that does.  Whilst I am unsure of the legality of the repair shop selling me a copy of their installation disk, they didn't sell me a license to use Windows just a means to reinstall one for which I already have a license.  Remember, it is the number on the CoA (on the bottom of the laptop) that is used to authenticate the Windows installation.
 * During the Windows installation, I simply read the number off the CoA that was stuck to the bottom of the laptop. When Windows Genuine Advantage leapt into life and told me I had to authenticate Windows, I simply followed the instructions on screen.  Because most of the hardware was the same and the product key from the CoA was the same as the previous installation, the authentication code matched that already recorded my Microsoft.  Astronaut (talk) 01:06, 18 January 2011 (UTC)
 * There are a lot of cheap (eg £5) brand-new Windows XP instalation disks available on eBay. As far as I recall without finding the disk, they are labelled as being for Compaq computers I think. Do you think i could do the above with them? It is also possible to find the liscencse number on the disk even if you do not have a label. Some software called "jellybean" is one of the programs that can retrieve it. However, I intend some day soon to switch to a free operating system, and thus leave all these worries behind me. 92.28.254.64 (talk) 01:22, 18 January 2011 (UTC)
 * I would be very careful unless you happen to have a Compaq PC which is a close match. These are probably the normal OEM disks (ie. not the generic OEM disks with the hologram) and therefore cannot be used in the way I describe above.  If I understand correctly, there are only three kinds of disk - retail, normal OEM, and generic OEM.  The product key is not held on the disk and therefore cannot be read - you do need the Certificate of Authenticity.  The Jellybean product you mention, reads the registry of an already installed Windows OS, and tells you the product key - useful if your CoA is missing or illegible, but it won't crack a CD and magically give you a valid product key.
 * If you are going to buy a used laptop, I would insist they show it working and provide you with everything they have, including the installation disks. If you are just given a laptop, you can try to refurbish it but you still might end up having to dump it.  I was lucky with the three I was given, getting them all working with a mixture of spare parts I already had and being able to buy an OEM installation disk for minimal cost.  But I was quite prepared to strip them all down for parts - which would have been useful had I decided to go ahead and do PC repairs in my spare time.  Astronaut (talk) 02:20, 18 January 2011 (UTC)
 * This may be of interest: http://www.technibble.com/how-to-tell-what-type-of-windows-xp-cd-or-license-key-you-have/ The disk I have, still unused, may be Dell and may have a liscence sticker on it as far as I remember. Knowing the liscence number found by Jellybean may be of use if you want to re-install. 92.28.254.64 (talk) 03:39, 18 January 2011 (UTC)

Problem with number rounding error
I've written a short program in GWBasic that involves adding up two numbers to check that they exactly match another number. If it finds a discrepancy, it stops. The program processes several sets of numbers correctly, but stops when it has to add 1210.42 and 174.65 to check if their total is the same as 1385.07. It says the numbers are different, when actually they are the same.

The two numbers both display on the screen as 1385.07, but when I subtract them and multiply the result by 100 I get a value of "-1". When I multiply by 10000 I get "2". I suppose the problem must be due to rounding errors and binary representations of decimal numbers.

What can I do to fix this problem please? Thanks 92.15.8.13 (talk) 13:28, 17 January 2011 (UTC)
 * In GWBasic probably not much. Can you rescale your problem so that only integer numbers appear? In your example, just multiply all numbers by 100, add up, compare. In general, if you deal with arbitrary decimal expansions, floating point is in nearly all applications the most convenient format, but in that case you must expect and learn to live with rounding errors. There are numbers with a finite decimal representation that have no finite binary representation, so that rounding is almost unavoidable. Why do you need an exact match? If its a science problem, your inputs are not constraint to arbitrary precision. If its financial, you are only interested in full cents (or whatever the smallest currency subdivision is). --Stephan Schulz (talk) 13:41, 17 January 2011 (UTC)

Will try calculating with pence, not pounds. Is there a way of telling GWBasic that these numbers are integers only, and if I do that can I expect it to ignore any hidden fractional part? 92.15.8.13 (talk) 13:51, 17 January 2011 (UTC)


 * You type a % after the variable name. 81.131.45.34 (talk) 14:22, 17 January 2011 (UTC)
 * (ec):I'm not sure - I don't use or know GWBasic. Back when I did BASIC (of the Sinclair BASIC and Locomotive BASIC flavours), variables were untyped values were typed, and the system would use integer arithmetic on integer values, but convert automatically to floating point when necessary using only half-understood (by me) rules. Many modern programming languages allow you to declare the type of the variable. In many BASICs, int(X) will coerce X to integer, IIRC. --Stephan Schulz (talk) 14:31, 17 January 2011 (UTC)


 * According to the GWBasic documentation, single-precision floating point values are only guaranteed accurate to six significant digits. If you use double-precision, you get 17 digits of accuracy.  You can make a variable double-precision by using # in its name instead of !. (I found the documentation here.) Looie496 (talk) 17:54, 17 January 2011 (UTC)
 * If the original poster intends to work with numbers that have two decimal places, and wants to test numbers for equality, he should avoid all forms of floating-point arithmetic. As Stephan Schulz commented above, he should convert his numbers to integers and work with those. Testing floating point numbers for equality is a well-known tarpit. Converting decimal numbers to binary (internal to the computer) and back again messes up the comparison since simple decimal fractions may have no exact counterpart in binary. Roundoff due to the binary conversion will spoil any tests for equality.  See our article on floating point for background. EdJohnston (talk) 18:06, 17 January 2011 (UTC)


 * If you must compare floating-point numbers, do not check for exact equality. Use the following trick: (A ≈ B) → (A-B)≈0 → (A-B)2≤ ε for small epsilon.  Select a suitably small one for your purposes.  In other words, replace IF A=B by IF ((A-B)*(A-B))<1E-6.  Nimur (talk) 21:06, 17 January 2011 (UTC)
 * That's a good trick. (The purpose of the squaring is to ensure the result is positive, I gather.) 81.131.47.204 (talk) 22:18, 17 January 2011 (UTC)
 * I think it's more usual to use abs(A-B) < epsilon, so as to avoid a floating-point multiplication (though it's unlikely to make much difference unless you're doing huge numbers of comparisons). AndrewWTaylor (talk) 12:42, 18 January 2011 (UTC)
 * When using this trick, you should also be aware that it breaks transitivity. A ≈ B and B ≈ C does not imply that A ≈ C.  I believe that there's no way to compare floating-point numbers for equality that doesn't cause unexpected behavior in some way.  My brother once implemented an arbitrary-precision math library, which would calculate as many digits as it needed automatically.  Testing for equality was not very useful, though, because if you tried to compare two numbers that were equal, it would diverge as it would keep calculating more digits forever, looking for a difference.  Paul (Stansifer) 17:23, 18 January 2011 (UTC)

Thanks, I have changed to using pence instead of pounds, and now it works without any problems. I tried making the variables integers by putting % on the end, but that gave an overflow error. By the way, the Windows and Linux nearest equivalent to GWBasic seems to be SmallBasic. 92.28.241.29 (talk) 00:07, 19 January 2011 (UTC)

[SOLVED] Auto config messed up display
Hi all,

I have a HP w19 monitor (19") and yesterday, when I pressed the auto config button, the display shifted almost 4 inches to the right, leaving a black on on the side. I tried pressing the auto button again, but the screen remained shifted. Nothing has been fruitful thus far. The display seems to think that the center of the screen is 4 inches right of where it used to be and I can't convince it any differently. If anybody has any ideas, please chip in. I'm tearing my hair out over here. 170.140.169.129 (talk) 19:45, 17 January 2011 (UTC) (P.S. When I take a screenshot, it takes a picture of the normal display without the black bar, not what is currently being shown on the screen)
 * This is what I have attempted so far:
 * 1. Adjusting the horizontal position using the built in monitor menu
 * 2. Resetting the monitor to the factory settings
 * 3. Adjusting the resolution to the lowest possible (640 x 400) and then back all the way up (1400 x 900)in Windows' display options
 * 4. Adjusting the resolution in Nvidia Control Panel (I have a 8800 GTX, onboard is a 6150 LE)
 * 5. Going into a game and adjusting the resolution from there
 * 6. Unplugging the monitor and waiting for 15 seconds
 * 7. Mashing the auto config button repeatedly with increasing frustration
 * 8. Shouting at the monitor
 * 8. Shouting at the monitor
 * Download and install its drivers? Louder shouting? Check the data cable is plugged in properly? 81.131.68.227 (talk) 20:29, 17 January 2011 (UTC)

Unfortunately, none of that worked. Is there any software that lets you control screen position? I've tried Display Tuner and it didn't work. —Preceding unsigned comment added by 170.140.169.129 (talk) 21:34, 17 January 2011 (UTC)

Fixed the problem by plugging the screen into my roommates's laptop and cycling through the display modes. 170.140.169.129 (talk) 00:04, 18 January 2011 (UTC)

Weird noise from hard-drive
Just a few moments ago, my computer made this weird whirring sound without explanation, and now it stopped. Nothing else has occurred. What the hell? 24.189.87.160 (talk) 21:17, 17 January 2011 (UTC)


 * When the ambient temperature is really cold, like now in the Northern Hemisphere, I've noticed my laptops make a weird murmur-like sound, like a fan that needed some oil. After they boot up (and warm up), it stops. Could this be what you're reporting? I haven't noticed any change in performance with my laptops, so if that's what it is, I wouldn't get too worried.--el Aprel (facta-facienda) 22:10, 17 January 2011 (UTC)


 * Is it possible that our questioner is referring to the case of a desktop or tower computer when mentioning the hard-drive in the heading? This is a common misunderstanding. If it is the case, the noise could simply have come from the fan in the power supply having a transient wobble. Can our questioner please clarify what he or she means by "hard drive"? HiLo48 (talk) 22:32, 17 January 2011 (UTC)
 * I meant the hard drive in my laptop (at least that's where the noise seemed to have come from), but thanks for the info about cold weather causing it. It is freezing where I live. 24.189.87.160 (talk) 22:51, 17 January 2011 (UTC)


 * It is probably thermal recalibration or something else harmless. You could look at the drive's S.M.A.R.T. parameters to see if it has noticed any danger signs. One freeware Windows program that will show SMART parameters is System Information for Windows. -- BenRG (talk) 01:30, 18 January 2011 (UTC)


 * The above comments notwithstanding, now would be a good time to ensure that you have a current backup, just in case. Mitch Ames (talk) 10:50, 18 January 2011 (UTC)

Professional Website for Under 500$?
So, here's the deal. I am working with a team and we need a website. None of us have much HTML experience however, only a little. We were wondering what the best way to get a website for under 500 dollars would be. Should I be looking at website designers, finding a website builder online (akin to Website Tonight but allows us to host on our servers), or should we just buy something like Dreamweaver and suffer through the learning curve. I might be missing something that could be found in an article on Wikipedia which is why I'm asking here.

We have servers, just no design skills.--128.54.224.231 (talk) 21:47, 17 January 2011 (UTC)
 * If your website is reasonably straightforward, you should learn HTML, and design your website yourselves, because it is very easy to learn. A functional website need not be complicated to design; and there is no shortage of web-based information, tutorials, and instructions.  Numerous pre-fabricated web content "frameworks" exist if you need more complicated features, like an online shopping cart, a forum, or a "blog" style interface.  Do you need help locating technical resources for learning basic web design, or artistic/design style guidelines, or some other resource?  Nimur (talk) 23:38, 17 January 2011 (UTC)


 * KompoZer is regarded as the best free HTML editor. 92.28.254.64 (talk) 00:12, 18 January 2011 (UTC)


 * I can build you a web site for under $500. Just send an [mailto:turbo_benar@hotmail.com e-mail] with exactly what you want on the web site. I usually make sites in Flash, but if you prefer pure HTML, I can do that, too.--Best Dog Ever (talk) 00:57, 18 January 2011 (UTC)


 * Or, if you'd rather not hire a designer, you can purchase a nice template from templatemonster.com for anywhere from $50 to $80. You can then open the template in an HTML editor of your choice and customize it. I think Microsoft Expression is an easy program to use for this purpose. If you'd rather make one from scratch yourself, look at using Adobe Fireworks or Adobe Photoshop, which can both export images as HTML slices, and allow you to draw things and then move them freely across the screen -- something that cannot be done with ease in other types of site editors.--Best Dog Ever (talk) 10:15, 18 January 2011 (UTC)
 * General web templates are the way to go if you're not planning to have your site custom made or simply don't have the time/skill/$$$ to do so.Smallman12q (talk) 00:04, 19 January 2011 (UTC)

capacitive touch or resistive touch.....?
Hi, I am planning to buy a touchscreen cell phone. and I am really confused that i should go for a capacitive touch or a resistvie touch.. Please tell me which one is durable ... I know that capacitive is more responsive than a resistive touch and it feels good to operate a capacitive touch than a resistive. But I want to know which one have longer life capacitive or resistive as I know resistive is cheaper than capacitive.

I have selected two cell phones to buy both have same price but one with capacitive touch has 2MP camera and not having a goood look and other with resistive has 3.5MP camera with a stylish look.......please suggest me for which one I should go.. —Preceding unsigned comment added by 220.225.96.217 (talk) 22:44, 17 January 2011 (UTC)
 * A capacitative touchscreen typically has a front made of glass or hard plastic and a screen protector can be placed over the top for additional protection. A resistive touchscreen has a soft surface that is physically depressed and so can't be protected in the same way.  So a capacitative screen is less prone to accidental damage. --Colapeninsula (talk) 10:23, 18 January 2011 (UTC)

Is android worth it?
I wonder..... does android OS worth it the response it is getting and the people who are mad for it....? —Preceding unsigned comment added by 220.225.96.217 (talk) 23:46, 17 January 2011 (UTC)
 * Yes, it is very much worth it IMO. You can read online reviews of Android phones and find out for yourself. 24.189.87.160 (talk) 00:05, 18 January 2011 (UTC)
 * And IMO, iOS is better and I'd prefer that. But then that's the thing about opinions, you'll have to make up your own.  Dismas |(talk) 02:19, 18 January 2011 (UTC)

Worth it compared to what? iOS? I'd say certainly if you want to be able to modify/control it more easily. There are better OSes, but they have much lower market penetration at the moment (MeeGo & others), which means fewer devices and less momentum. ¦ Reisio (talk) 02:29, 18 January 2011 (UTC)

Can iTunes application on Windows play purchased movies?
If I buy a movie on my iPhone and back it up to my Windows XP computer using the iTunes application that knows about my account, will I be able to watch the movie on my PC? Peter Michner (talk) 23:53, 17 January 2011 (UTC)

Yes. I've watched movies I bought on iTunes and proceeded to watch it on my computer. — Preceding unsigned comment added by General Rommel (talk • contribs) 01:37, 18 January 2011 (UTC)