Wikipedia:Reference desk/Archives/Computing/2010 May 10

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May 10

Ultimate Boot Disk

Contrary to my title, this isn't specifically about UBCD. I have a long-term project I'd like to work on, but have sort of hit a wall in my process: I'd like to create a bootable disk (preferably USB) with all my favorite technician tools on it. Anti-virus software, backup tools, system restore tools, etc. I would like it to be configurable so that I can add new programs at a later date and I need it to boot quickly, so in general I will want to avoid loading a WinPE environment when possible (although I would like the option to run WinPE for the tools that require a Windows environment to run of course). I was thinking something similar to Hiren's BootCD in style, but I have my own tools I'd prefer to use rather than Hiren's.

So the tl;dr version: I want a USB stick with a configurable boot loader that has the option to load several different diagnostic/repair programs on the same stick.

My main problem here is that I do not understand boot loaders very well and am not quite sure where to look nor what will accomplish my goals and what learning I need to do in order to be able to create this disk. I was thinking GRUB4DOS could work, however I am new to bootloaders and so I am terribly confused by it.

Does anyone here have any experience building their own boot disks and wouldn't mind posting some links, how-to's, or otherwise point me in the right direction? Would be much appreciated, thanks!

Amordea (talk) 02:50, 10 May 2010 (UTC)

Have you seen our article, Ubuntu Live USB creator, and its project page? This may do exactly what you are looking for. Writing your own bootloader is not easy; I don't think you need or want to do this from what you have described above. All you want to do is use a bootloader to run a system from a USB stick. Nimur (talk) 03:04, 10 May 2010 (UTC)

Thanks Nimur. As far as I can tell, this particular live USB creator seems geared towards Ubuntu installs, which isn't quite what I'm looking for.

However I did pursue other live USB creators in the meantime and in the process uncovered a nice little program called Multiboot USB. This is very close to what I had envisioned (although preferably would also have persistence, but at this point I'd be happy just to get something functional), with the glaring exception of its small functional program list which is mostly incompatible with my needs. I decided to attempt to muck around with some of scripting in it anyway and I did get two of my unsupported programs to boot, however they would also crash soon afterwards due to reasons beyond my (admittedly limited) understanding.

I ought to elaborate some to clarify what I am looking for: I am mostly servicing Windows PC's. While I could carry a stack of rescue CD's with different functions and/or deal with what ships with other rescue multi-tools, I figure it makes more sense in the long run to learn how to build a portable multi-tool which contains all my programs in one easy-to-carry item. I want this tool to boot things like AVG's rescue CD, ERD Commander, Acronis TrueImage's boot CD, and any other tools I pick up along the way and have them all contained conveniently in one unit.

This task might just be beyond me. But I was sort of hoping such a functional and flexible tool already existed somewhere and that I was just too blind to see it.

Any other help would be most welcome.

Amordea (talk) 06:34, 10 May 2010 (UTC)

torrent subtitles

i downloaded a .avi movie and it came with subtitles but how do i "add" them and make em work? —Preceding unsigned comment added by Tom12350 (talk • contribs) 04:32, 10 May 2010 (UTC)

If you're on windows, try Media Player Classic. It has support for those kind of subtitles. Just put the video file and the subtitle file in the same folder and open the video in MPC. (I don't remember if they're on or off by default. You can toggle them by clicking in the "play" menu.) APL (talk) 07:14, 10 May 2010 (UTC)

VLC also does subtitles very easily; if they are in the same folder, you can find them on a Subtitles menu. --Mr.98 (talk) 12:31, 10 May 2010 (UTC)

I know someone who dislikes the way VLC handles subtitles although I can't remember why. I believe it has improved in recent versions but I'm not sure if all the major issues this person had have been resolved Nil Einne (talk) 13:42, 10 May 2010 (UTC)

Well, that's kind of vague. ;-) I tried to load up subtitles once in VLC and got a lot of garbage, but when I downloaded the latest version, it worked better. It seems pretty straightforward to me at the moment. --Mr.98 (talk) 13:48, 10 May 2010 (UTC)

i pu them in the same folder but where do toggle them by clicking in the "play" menu. where is the play or Subtitles menu. —Preceding unsigned comment added by Tom12350 (talk • contribs) 18:38, 10 May 2010 (UTC)

What software are you using to view the film? Did you download MPC or VLC like was recomended above? APL (talk) 19:44, 10 May 2010 (UTC)

yes i downloaded both wheres the subtitles button for them? —Preceding unsigned comment added by Tom12350 (talk • contribs) 21:51, 10 May 2010 (UTC)

In "Media Player Classic" click on the "play" drop-down menu, click on the "subtitles" sub-menu, then select the subtitle file from the list. In VLC, click on the "Video" drop down menu, "Subtitle track" sub-menu, and either select your subtitle file from the list or select "Load file..." to select the file manually. APL (talk) 00:44, 11 May 2010 (UTC)

i tried that but it didnt work —Preceding unsigned comment added by Tom12350 (talk • contribs) 07:22, 12 May 2010 (UTC)

is this a BST? if so, how would I begin to implement it?

I'm trying to prepare for a CS exam... so I'd thought I'd try to implement a random project on my own. I'm chemically inclined, so I figure it would be good to try to compile a sort of symbol table that would store the solubility equilibrium constant between two ions. Basically for every pair of ions (or types of ions) there is an associated solubility constant. Only, I have trouble trying to extend the 1 key ==> one value concept to a sort of "multivariable" equivalent of a function. Any ideas? John Riemann Soong (talk) 07:57, 10 May 2010 (UTC)

And of course as with any ST, it should be dynamic, e.g. it is easy to implement methods adding or removing relations. John Riemann Soong (talk) 07:59, 10 May 2010 (UTC)

It depends a bit on the language you write your implementation in. However, in general you will want a hash that incorporates both objects. In java either make an object that encapsulates both objects or create a map from a set of ions. Taemyr (talk) 08:41, 10 May 2010 (UTC)

Is there any way to do it using a BST implementation? The issue is that I need to remove the redundancy -- the Ksp for Ca++ and acetate is the same as the Ksp for acetate and Ca++. If I change the Ksp for one pair how would I efficiently change the other? etc. John Riemann Soong (talk) 20:03, 10 May 2010 (UTC)

extends Comparable<Key> for a molecule datatype?

I actually don't really know how this Comparable thing works in Java... they kind of glossed it over in class. I'm trying to write a program that would compare two chemical compounds by chemical structure using a procedure based on Cahn–Ingold–Prelog priority rules. (For example, chloromethane > methane. I intend to implement a recursive definition using a user-defined "molecule" datatype.

Firstly, when comparing two molecules, we first determine whether it is organic or inorganic (by whether it contains carbon). The rules diverge for each type (i.e. if it is inorganic, we use another set of rules). If it is organic, we compare by # of carbon atoms. If there's a tie, we look at the carbon with the substituent with the highest atomic number. So on and so forth. The basic idea is that I guess I want to maybe define a "compare" function.

I admit I don't get how generic <Key> works at all. Is the way I want to implement Compare for molecules going to work with generic data types? John Riemann Soong (talk) 09:32, 10 May 2010 (UTC)

Yes. Just say class Molecule extends Comparable<Molecule>. The generic is there in case you want more flexibility in what you compare with. Taemyr (talk) 10:03, 10 May 2010 (UTC)

No, there's no need to extend Comparable<T> for this; your class should implement it. The generic just allows you to specify the type of object it's okay to compare, so in your case, you would implement Comparable<Molecule>, where Molecule is the (super)class of your chemicals. Basically what Comparable does is require you to write a method that returns an int when given another Molecule to compare. Read the documentation I linked to for more about what the sign (+/-) of the returned int means. Once you implement Comparable, you can use a sorting method (like one of those in the java.util.Collections class) to sort a List of Molecules. Let me know if you need anymore help.--el Aprel (^facta-_facienda) 18:54, 10 May 2010 (UTC)

Avast! v. Microsoft Security Essentials - which is better?

I thought Microsoft Security Essentials was just a malware scanner, but when trying to install it, I found out that its a run-all-the-time program. I currently have the free version of Avast! installed. Which is better, Avast! free edition, or Microsoft Security Essentials which is also free? Thanks. 84.13.53.169 (talk) 13:19, 10 May 2010 (UTC)

According to a recent article in Maximum PC magazine,[1], Microsoft Security Essentials[2] is better than Avast!.[3] Personally, I use AVG Anti-Virus which is also available for free.[4] A Quest For Knowledge (talk) 13:34, 10 May 2010 (UTC)

Yes, AVG is a great little free program.Chevymontecarlo. 16:00, 10 May 2010 (UTC)

Little? I've personally found it to be quite bloated and resource hungry. Avira Free Antivirus is better imo, at least in terms of performance, but I am unsure how it performs in terms of virus detection compared to AVG 82.44.55.254 (talk) 17:48, 10 May 2010 (UTC)

Thanks, although after reading it I'm not sure that the article does indicate that MS Security Essentials is better than Avast! 78.146.176.116 (talk) 19:27, 10 May 2010 (UTC)

The print version includes a rating for each product on a scale from 1 to 10 (higher = better). For whatever reason, the online version of this article doesn't include this rating. I remember that MS received one of the higher ratings, I believe an 8. I don't have the magazine with me, but if I have time, I'll check tonight what each scored. A Quest For Knowledge (talk) 19:38, 10 May 2010 (UTC)

You can get a free PDF of the print edition. MSE got an 8, and Avast! got a 5. -- Coneslayer (talk) 19:52, 10 May 2010 (UTC)

Avast is definitely my first choice; Used to use AVG, Avast is much less intrusive and seems to do just as well, if not better. I recall a study that concluded Avast was more or less the best AV at the price point. Riffraffselbow (talk) 00:24, 14 May 2010 (UTC)

Looking for example graphical UIs for programming IF....ELSE...ENDIF blocks with boolean logic

Background

At work, we have an application that (among other things) requires end users to enter small snippets of code. These code snippets are rules which are executed by a rules engine at run-time. Usually, these rules are only a few lines long. Generally, the code follows the form:

//pseudocode
IF ((variable1 > value2 AND variable3 = value4) OR (variable5 = function6(variable7)) THEN
//do something
ELSE
//do something else
ENDIF

Although our users are bright (they all have engineering degrees), they are not programmers and dislike having to write programming code. For the next version of our software, we would like to create some kind of graphical user interface that would allow users to 'create' programming code without having to type it all in. IOW, we want to create some kind of point-and-click GUI that would allow then to write code with a minimal amount of typing. There are some things that we realize that our users will have to type, such as mathamatical formulas (but using an Intellisense-type text editor), but we'd like all the other code to be graphically generated.

Standing on the shoulders of giants?

I have some ideas of what such a UI might look like, but it seems to me that this problem (creating a point-and-click GUI to write IF....ELSE...ENDIF blocks) is not something unique in the history of software development. But for the life of me, I can't think of any apps with this sort of GUI. So, here's my question. Can anyone point me to any apps (or web pages, whatever) I can use as examples in creating my GUI? I figure that someone else, brighter and more knowledgable than me, has already thought of this problem before and come up with some ideas. A Quest For Knowledge (talk) 13:22, 10 May 2010 (UTC)

Check it out: Visual programming language and Category:Visual programming languages. Personally I find Scratch the most straightforward looking (see e.g. screenshots here), but I'm not the target audience. --Mr.98 (talk) 13:42, 10 May 2010 (UTC)

Simulink and LabView, both commercial software tools, are widely used for this sort of task. Nimur (talk) 15:32, 10 May 2010 (UTC)

Try looking at Microsoft Excel's insert function capabilities. "Insert If", for example is similar to what you describe. Alfrodull (talk) 22:37, 10 May 2010 (UTC)

iTunes can be used as an example. If you're creating a "Smart Playlist", you can select as many criteria as you like and any songs that fit the bill, get onto the playlist. e.g. Genre = Rock, Length > 20:00, Composer = Pink Floyd. --Dismas|^(talk) 07:53, 11 May 2010 (UTC)

Viruses

Are there any computer viruses that can actually cause physical damage to computers (such as destroying/damaging hard disk and RAM) as some chain mails claim? 202.129.235.22 (talk) 15:16, 10 May 2010 (UTC)

No – ╟─TreasuryTag►constabulary─╢ 15:21, 10 May 2010 (UTC)

The caveat should be, "no virus can damage the hardware of a well-designed commercial personal computer." See our article, brick (electronics). In sloppily-designed devices, particularly mobile/embedded systems, it is possible for software to irreversibly damage the hardware. There are also varying degrees of "irreversible." In some cases, if firmware is damaged, it can be reprogrammed using additional devices/cables. It is also possible that malfunctioning software could destroy hardware and render the unit unserviceable. Nimur (talk) 15:40, 10 May 2010 (UTC)

The Chernobyl virus has some info about this.--TrogWoolley (talk) 16:10, 10 May 2010 (UTC)

Followup question: Years ago, when CRT monitors were nearly universal, I remember reading that changing their screen resolution too quickly — many times a second — could damage the monitor, and there was speculation that this could be a form of computer virus that could damage hardware. I'm having trouble googling any mention of this; is any of this factual? Comet Tuttle (talk) 18:28, 10 May 2010 (UTC)

I had a similar thought about cd drives; could a virus make the cd drive spin too fast, which would shatter the disk inside? 82.44.55.254 (talk) 19:50, 10 May 2010 (UTC)

That sounds unlikely unless the CD is already cracked. Are the speed limiters physical in modern drives? At one time, the limitation was in firmware that I suppose could be modified by a virus. It was reported that the old 5.25 inch floppy drives could be damaged by repeatedly seeking a non-existent track past the physical stop, but I never succeeded in causing damage when trying to write extra tracks. Dbfirs 06:53, 11 May 2010 (UTC)

I recall (in some 1985-1890?) have heard about the possibility to de-calibrate HD heads by repeatedly forcing it to seek past the last physical cylinder. Possibly there were some poorly designed devices, where the on-board software did not validate the head positioning command parameters, but I doubt it.
What concerns CRT monitors, some of them were prone to failure whan the video card was set to generate too high refresh frequency. Even now, if you are using Windows, see the monitor settings: Control panel → Screen → tab Settings → button Advanced → tab Monitor → drop-down list Refresh frequency and checkbox Hide modes... below it (some names may differ slightly, I translate them back to English from Polish version). There is a comment there, saying something like 'Un-checking this option allows you to choose display modes which your monitor may not handle properly. This may cause the monitor unusable or hardware damage' (sorry againg for my poor English). --CiaPan (talk) 07:32, 11 May 2010 (UTC)

Purely speculation on my part, but given that you can alter voltage settings via software (for overclocking purposes), it seems theoretically possible a virus could do this too at an intentionally malicious level that could damage the circuitry. I have never heard of such a virus in circulation, but it seems theoretically possible? Or I could be wrong. Amordea (talk) 11:29, 12 May 2010 (UTC)

computer power supply question

I have a computer with a 500W power supply, and the hardware inside currently uses 415W. If I was to upgrade my video card, the new requirements would take 475W. Would this make it more likely for my power supply to fail, since it would be running at 95% capacity? Googlemeister (talk) 15:47, 10 May 2010 (UTC)

I bet that Dan's Data has covered this, I wasn't able to find anything more specific than this general discussion after a couple quick searches. Paul (Stansifer) 16:58, 10 May 2010 (UTC)

There are a few issues I see, besides whether it will lead to PSU failure: (1) Sometimes PSU power ratings are simply bogus. It's possible that your 500 W power supply has never been able to supply 500 W. (2) As it ages, the PSU may be less able to supply its rated power, so even if it could supply 500 W when it was new, it might not be able to anymore. See Footnote 4 at this PSU calculator. (3) The power that it can supply is divided up in a certain way between its various voltages and rails. If the system you're building requires 500 W, but it's divided up differently than the 500 W in the power supply, some component will not get enough power. -- Coneslayer (talk) 17:09, 10 May 2010 (UTC)

If you're underpowered or close to capacity, then your components would do more 'work' in getting power from your PSU and this is one of the most common causes of overheating. I would keep at least 20% fat and there would be no harm in getting yourself at least a 600W PSU which would also put less strain on the PSU and your PC. Sandman30s (talk) 18:08, 10 May 2010 (UTC)

What kind of computer do you have? Because unless you're using a power metre to measure the draw, I somewhat doubt your computer really uses 415W (at a guess, you'd need a fast or old quad core and SLI/Crossfire to get even close to that). Most PSU/power draw calculators just as the maximum possible load of every single component usually with significant headroom added in which can never occur in practice, no matter what kind of stress test you actually use. Also manufacturers of products, when recommending power supplies have a tendency to overestimate what you need for a variety of reasons including the fact many powersupplies are vastly overated and it's easier for them to do that and reduce the chance the PSU will cause problems particularly for people who don't know what they're doing then it is to offer proper PSU requirements. If you don't have a power metre, take a look at SPR to get an idea of the real power consumption of your system (I'd recommend you ask there if you need further help) e.g. [5] [6] [7] [8]. Also while getting a bit old [9] is still useful.

Now back to the original question, if you really need 485W then it may be slightly risky to use a 500W PSU but it depends a lot on the quality of your PSU. As others have mentioned there are issue like rail loadings and PSUs not supplying their rated capacities. And bear in mind many cheaper PSUs are rated at a silly temperature anyway, like 25 degrees C. See [10] for more. Also a good PSU should shut down if overloaded but crappier PSUs may sometimes just die, and there's a possibility of taking something out with it.

However I disagree there's no harm in getting 600W PSU. If your system doesn't really need anything close to it then it's a waste in many ways. Firstly since it's resonable to presume cost matters to you, there's no reason to spend money on something you definitely don't need. Note as well it would be far better to get a high quality lower rated PSU, e.g. Antec, Corsair, Enermax, then to get a crappier higher rated PSU. (Although this applies whatever, if you really need 600W I would recommend you spend the extra to get a good PSU, you must have a rather fancy system to need that so hopefully the cost won't be a problem.) More importantly PSUs tend to be quite inefficient at low loads (in some cases you may even have problems if the load is too low). If you aren't continually stressing your computer, then it likely spends a great deal of time idle and with most modern computers, idle usage can be very low. This means your PSU may spend a lot of time at a rather inefficient range if you get an overly high rated PSU. If you get or have a high quality PSU then it's likely compliant with the 80 PLUS standard, this means it needs to have 80%+ efficiency at 20% load so it isn't as bad as some of the older crappier PSUs but 20% of 600W is 120W and there's a resonable chance the usage will be lower then this depending on what it is.

In the same vein though, PSUs tend to be most efficient at around the 50% or so mark. So you also ideally don't want to your PSU to be continually using 95% load.

Nil Einne (talk) 00:50, 11 May 2010 (UTC)

Power Cut

Say if there's a power cut and of course the computer would go off. Is there a way to make a computer automatically start up again when the power comes back? 82.44.55.254 (talk) 17:45, 10 May 2010 (UTC)

Many BIOSes have a setting to power on after a power outage. Go into your BIOS settings and look around. --Spoon! (talk) 17:59, 10 May 2010 (UTC)

This page has simulated screenshots of the popular Phoenix BIOS; the bottommost screenshot shows the option you want, called (on that particular brand of BIOS) "Restore on AC/Power Loss". Comet Tuttle (talk) 18:07, 10 May 2010 (UTC)

You can of course use an Uninterruptible Power Supply to keep the power going for a long time. Of course the bigger your UPS, the longer it will have power for. Sandman30s (talk) 18:00, 10 May 2010 (UTC)

iTunes bit-o-song selecter slider

1. What is that thing called? You know, where you pull the thing back and forth and it changes your place in a song... 2. How can I make it longer? I have an mp3 that's two hours long and when you get to that point you don't get much control with the pissant thing you get as default. Vitriol (talk) 17:49, 10 May 2010 (UTC)

It's called a slider, as you correctly mentioned in your title.--el Aprel (^facta-_facienda) 19:14, 10 May 2010 (UTC)

Yeah, but there's also the volume slider. Vitriol (talk) 22:21, 10 May 2010 (UTC)

Just a position slider. In editing software (such as Goldwave) you can zoom in to obtain any degree of positional accuracy. Dbfirs 06:35, 11 May 2010 (UTC)

I've never known of any way to change the size of that slider. Since the majority of what iTunes is built for is (was?) a 4 minute song, there isn't too much need for a lot of accuracy in the slider. After all, it's not a sound editing tool where you're trying to get just one clip of a song and need to place the slider on an exact beat. Dismas|^(talk) 07:42, 11 May 2010 (UTC)

Battery

Hi, my rtc battery is dead, finding another one is very difficult. Does exist a sw that synchronizes not only the time but the date as well with a time server in internet? t.i.a. --87.5.122.52 (talk) 20:41, 10 May 2010 (UTC)

(I've added a section title to your question so we can see it's not part of the above thread.) Are you certain that you have a nonstandard CMOS battery? It's like a US$5.00 part on desktop machines. There certainly are applications that synch your computer's time with a big clock on the Internet; what OS are you running? Comet Tuttle (talk) 21:58, 10 May 2010 (UTC)

I doubt that there is a way to synchronize time without synchronizing the date. (Usually, the date/time information is stored internally as seconds since January 1st, 1970; it would take extra effort to not sync them both). You probably want a Network Time Protocol client. Paul (Stansifer) 22:49, 10 May 2010 (UTC)

alas my pc is a laptop.. I found many synchronizer, but all of them need a manual adjusting of the date. Thank you --87.5.122.52 (talk) —Preceding unsigned comment added by 217.194.34.103 (talk) 07:53, 11 May 2010 (UTC)

It will be easier for us to help you if you say what make and model the laptop is, and (as requested above) the operating system. --Phil Holmes (talk) 08:51, 11 May 2010 (UTC)

It's an acer travelmate 661lci, the os is win xp --87.5.31.150 (talk) 18:07, 11 May 2010 (UTC)

With Win XP, the OS provides date/time synch. Open the clock from the system tray, click the Internet time tab, and click Synchronise now. --Phil Holmes (talk) 13:45, 12 May 2010 (UTC)

Special configuration parameters of the Windows time sync service (for advanced users only!) are described here http://support.microsoft.com/kb/884776

You may also find helpful some of lnks on this page http://technet.microsoft.com/en-us/library/cc773061(WS.10).aspx (section Note) — or may be not:

• Configure the Windows Time service on the PDC emulator
  http://go.microsoft.com/fwlink/?LinkId=91969
• Configure a client computer for automatic domain time synchronization
  http://go.microsoft.com/fwlink/?LinkId=91376
• Configure a manual time source for a selected client computer
  http://go.microsoft.com/fwlink/?LinkId=91377

CiaPan (talk) 15:15, 12 May 2010 (UTC)

thank you for your advice, but the Synchronize service of xp needs a manual synch of the date, otherwise it doesn't work. The lonks you gave me doesn't apply on my xp home in workgroup (not in domain) --87.5.31.150 (talk) 20:12, 12 May 2010 (UTC)

Databases?

Is Pay Pal catergrized as a database? —Preceding unsigned comment added by 72.95.165.196 (talk) 22:45, 10 May 2010 (UTC)

PayPal certainly uses many databases. What distinguishes PayPal from, say, eBay (which also uses many databases), or CNN.com (ditto), or Facebook (again), or even Wikipedia (yeah), are qualities other than the fact that it uses a database. Any large site that has large amounts of carefully delineated information (e.g. names of users, accounts of transactions, articles, whatever) uses database technology. It is very widespread. I would not categorize a site "as a database" unless it does nothing but serve as the front-end for a database (e.g., the ARIN WHOIS database). --Mr.98 (talk) 22:53, 10 May 2010 (UTC)

"Database" has two typical meanings:

• An organized collection of data.
• A collection of data in a Database Management System, which is a software system to put data into non-volatile storage in a quickly-accessible, reliable, and safely-editable fashion. Almost every complex website (not to mention many other things) is backed by such a system (usually a SQL-style relational database).

So, in either sense, PayPal has a database, but that doesn't distinguish it from, say, Geocities. Paul (Stansifer) 03:38, 11 May 2010 (UTC)

questions on Wal-Mart

it has been said that the advantage that leading edge retailer such as Wal-Mart has over their competitors isn't technology but management. Discuss 2.what management, organisation, and technology facctors explain why Wal-Mart suppliers had trouble implementing RFID systems 3.How is RFID technology related to Wal-Mart business model? How does it benefit suppliers —Preceding unsigned comment added by Annor Brenyah (talk • contribs) 23:35, 10 May 2010 (UTC)

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our policy here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. --Mr.98 (talk) 23:45, 10 May 2010 (UTC)