Wikipedia:Reference desk/Archives/Computing/2009 November 6

= November 6 =

what is the difference between router, hub and switch
I am a student studing BE CSE... Please help me with the difference between hub,switch and router... I googled it... But couldnt get the point....

—Preceding unsigned comment added by 122.165.55.113 (talk) 04:47, 6 November 2009 (UTC)


 * To be as simple as possible... A hub connects network connections - it is a very dumb device. A switch connects networks, relaying traffic from one to another - it is a semi-intelligent device.  A router directs network traffic to where it needs to go - it is a very intelligent device.  In the real world, there is pretty much no difference.  Most hubs are switches.  Most switches are routers.  The definition all depends on what marketing was smoking behind the building that day. --  k a i n a w &trade; 04:49, 6 November 2009 (UTC)

Hi Kainaw... What is the exact thing you mentioned about semi intelligent and intelligent device... For what specific purposes we use switch and router... Please make it clear about switch and router... —Preceding unsigned comment added by 122.165.55.113 (talk) 05:04, 6 November 2009 (UTC)

Note that what is now called a hub used to be called a repeater. (To my mind at least, "repeater" is a better term because it more accurately describes what the device does. A "hub" was simply a central point where multiple connnections occurred, and could be a repeater, router or switch.) Mitch Ames (talk) 05:33, 6 November 2009 (UTC)

Thanks Mitch Ames... But could you please let me know about Switches and Routers in a better way.... —Preceding unsigned comment added by Atchays (talk • contribs) 05:36, 6 November 2009 (UTC)

To use a postal anology, the hub is a pile of letters from which each user can grab theirs; the switch is a set of piles of letters with each user's letters separate from each others; the router is a post office. --203.202.43.54 (talk) 08:28, 6 November 2009 (UTC)
 * Hub: Connect two or more computers to each other. They all share the bandwith of the device, so if two computers are transferring a lot of data between themseleves, a third computer on that hub, talking to a fourth one would not have much bandwith.
 * Switch: Connects two or more computers to each other. Does it better than the hub, and makes sure that computer 1 talking to computer 2 doesn't interfere with computer 3 talking to computer 4.
 * Router: Connects one network to another network. For example a router connects a business network to the internet. It "routes" information from one network back to the same network or to any other network it is attached to depending on where the information is addressed to.


 * Although (as most posters here have said) there's now not much difference between what switches and routers do and how they do it, historically it was always considered that a switch was a Layer 2 device, and a router Layer 3. --Phil Holmes (talk) 09:40, 6 November 2009 (UTC)
 * Yes. Nowadays a "switch" is typically a router optimized for high-throughput LAN connections with a lot of subnets. --Stephan Schulz (talk) 10:18, 6 November 2009 (UTC)

Missing math symbols.
When I look at Mathematical alphanumeric symbols all I see is a table of squares. Running Windows Vista and IE8, how can I display the proper symbols? I'm thinking of downloading a symbol pack or something similar. Thanks --The Dark Side (talk) 04:49, 6 November 2009 (UTC)


 * You'll need to install a font (or multiple fonts) with glyphs for those characters. See here for a good start. Bendono (talk) 05:11, 6 November 2009 (UTC)


 * I downloaded the Symbola font and installed it, but I still can't see the symbols. --The Dark Side (talk) 04:39, 7 November 2009 (UTC)


 * I've have this problem too, and have tried to download fonts to cure it without success. Why isnt it possible to simply have one font that includes everything?? 89.243.191.11 (talk) 19:58, 10 November 2009 (UTC)

Why do we need to use DNS while connectiong to internet
Myself trying to establish a internet connection need to enter the DNS provided by the Internet Service Provider. Why do we need to use DNS while connectiong to internet..... Whats the real purpose in it... Why are we using alternate DNS address... —Preceding unsigned comment added by Atchays (talk • contribs) 05:19, 6 November 2009 (UTC)


 * See my name, at the end of my post? the numbers? That's an IP address. Every computer connected to the internet is identified by an IP address like that. IP addresses are hard to remember, so there are names (like en.wikipedia.org) attached to some IP addresses. You need a way of matching the name to the address, that's what DNS does. Your computer says to a DNS server "what's the IP address for en.wikipedia.org" the DNS server replies with a number, your computer then finds the site by the number. --203.202.43.54 (talk) 08:31, 6 November 2009 (UTC)


 * ....and if you know the IP address, you can connect to the internet with without a DNS server, as in http://131.159.46.188. The problem is that IP addresses keep changing, either because there are actually multiple hosts behind the same name (to spread the load), or because IP addresses are reused when a host goes offline (this happens, in particular, with most users connected via DSL). You often have more than one server, because the function is critical to practical use of the net, so if your primary server is down, you have a fallback. Also see Domain Name System. --Stephan Schulz (talk) 09:00, 6 November 2009 (UTC)


 * (I believe you mean "... connect to the internet without a DNS server ...".) Simple analogy - a DNS server is a phonebook. You have a name (Stephan Schulz or en.wikipedia.org), and you look up the number (123-867-5309 or 208.80.152.2) which you can then use to dial the recipient. -- 128.104.112.237 (talk) 21:12, 6 November 2009 (UTC)
 * Very good analogy!Accdude92 (talk to me!) (sign) 21:14, 6 November 2009 (UTC)

W7- Graff Digitiser and sound card
Another W7 question... I upgraded my XP desktop to 7 Ultimate. I was forced to install my Graff Digitizer (tape to digital converter) in XP mode. The problem is, it requires my sound card (M100?) to work, and it can't find the card. The card was installed in 7, and the device manger says it works properly. Is there any way to salvage this in 7, or do I have to return to XP? Specs: Athlon X2 6000, 2X1GB DDR2 800, Asus P5K mb, WD 500GB HDD, ASUS EAH 3450 (512)

(Before you ask, Graff does say it can only work on XP.) Mxvxnyxvxn (talk) 06:49, 6 November 2009 (UTC)
 * I've had a driver issue with my vidcam and have to go back to XP to capture from tape. You can try to download a Graff vista driver if there isn't one for win7 yet. Or, use a downloaded driver for your sound card since Graff might have been looking for something specific in the driver software and win7 uses its own drivers. Dual boot to XP anyway for all those things that don't work; it's a normal step in a migration. Sandman30s (talk) 10:23, 6 November 2009 (UTC)


 * Have you considered a Virtual Machine running XP? --Phil Holmes (talk) 14:43, 6 November 2009 (UTC)


 * Windows 7's XP Mode is a virtual machine. --Andreas Rejbrand (talk) 17:35, 6 November 2009 (UTC)


 * (Sigh) It isn't worth the trouble... I think I'll just go back to XP. Thanks anyway. Mxvxnyxvxn (talk) 21:56, 9 November 2009 (UTC)


 * I've seen the thing not work even on XP. Take a look at "DTBuild.cfg" -- it looks like it's rather stupidly searching for sound cards by NAME.  For example, it wants "M-Audio Delta AP192 1/2", but the card is really named "Delta AP 1/2".  Now, I need to find out what serial port settings it uses, and I can make my own digitizer app.

Vista vs. 7
On the exact same hardware, which will have a better performance —Preceding unsigned comment added by 82.43.88.201 (talk) 10:38, 6 November 2009 (UTC)
 * Windows 7. This very same question has been asked previously. Try Ctrl+F on this page... --Andreas Rejbrand (talk) 10:58, 6 November 2009 (UTC)
 * Do you have a source for that? It's not that I don't trust you, I'd just like to see some verification of this, like performance charts or bar graphs of the two operating systems' performance. Thanks
 * Check out these two articles: . It seems that while there is ample anecdotal evidence saying that it is significantly faster/smoother, the people that make bar graphs only get marginal improvements over Vista. &mdash;Akrabbimtalk 13:02, 6 November 2009 (UTC)
 * Another example:, google is your friend in this case :). 192.234.122.9 (talk) 13:08, 6 November 2009 (UTC)

Awesome, thank you!

What are the differences between interface and valuetype in CORBA IDL?
I used the idlj compiler to compile two similar idl files ( one with interface X and one with valuetype X) and saw that both created XHolder.java and XHelper.java, only the interface created _XStub.java and XOperations.java and only the valuetype created XVauleFactory.java and its implementation XDefaultFactory.java, which included generated references to XImpl.java, which I had to create myself. I've looked at the generated code but I wonder if someone can crystallize into a simple sentence or two what general use/situation each is really meant for. Thanks! 20.137.18.50 (talk) 14:12, 6 November 2009 (UTC)

Where did my CD window go?
I have a Windows Vista XP, Italian laptop, and I am currently unable to view or burn CDs as the window doesn't appear when I insert the CD. What should I do about it? I've got loads of photos I need to download to CDs. Thank you.--Jeanne Boleyn (talk) 16:17, 6 November 2009 (UTC)
 * If you have XP, press the Windows key and e at the same time. This will bring up My Computer.  You can navigate to your CD drive in the left-hand tree view.  12.165.250.13 (talk) 16:27, 6 November 2009 (UTC)
 * And once there, you can create a shortcut for your desktop if you so wish.   D b f i r s   20:19, 7 November 2009 (UTC)

Is there a name for this bug?
I just found this bug in my code at work. I was using a for loop and an iterator, both over the same range, in conjunction, so the for loop would go over sequential values and check if it had reached the iterator. If it had, it got a value from it, and the iterator advanced. Now what had happened is, the for loop had actually been able to move past the iterator, so when it was checking if it had reached it, it never found it had. Is this a common enough bug to have a name for it? J I P | Talk 19:47, 6 November 2009 (UTC)


 * I doubt it -- it is just a control flow problem. This is why with for/next loops, one usually uses >= rather than == as the way to detect when you have hit a given point, though in theory one should not need to do this if it is programmed carefully. In theory, one should be aware at all times of what the possible ranges for a variable value is, though in practice, or with anything that works in parallel, there can be some sloppy slippage. --Mr.98 (talk) 20:01, 6 November 2009 (UTC)


 * Can you show us the relevant parts of your code ? I'd be interested to see it. StuRat (talk) 15:54, 7 November 2009 (UTC)
 * I'm not at all sure about how much I can show without revealing trade secrets, but here is a very basic sketch (C# pseudocode):

DateTime[] allDates = /* ... */; IEnumerator iterator = /* ... */; foreach (DateTime date in allDates) { DateTime nextDate = iterator.Current./*get next date*/; if (date == nextDate) { /* get the value */; iterator.MoveNext; } }
 * Now what happened was that it actually became the case that, so   was never going to be true, the way I originally wrote it.  J I P  | Talk 21:28, 7 November 2009 (UTC)


 * Well, I guess that means that Mr.98's advice to change the == to >= was right on the mark, then. StuRat (talk) 00:03, 8 November 2009 (UTC)
 * Actually, it wasn't exactly, but the idea was the same. In my real code, "get the value" depended on the date being exactly equal. So I just added a while loop before the if, checking if  was already past , and if so, then just discarding values until it matched it.  J I P  | Talk 18:15, 8 November 2009 (UTC)

Shutdown Menu
I've been messing around with my computer a lot (Windows XP), and I don't know what I did but the shutdown menu, in which there were three nice looking square buttons (Standby, Shutdown and Restart) have been replaced by a stupid looking drop-down menu with the same options (and Hibernate as an addition) instead. Also, the computer asks me for a password during log-on, and since I don't have one, all I have to do is press enter. But still, I see all this as an unnecessary waste of time, and would be real glad if someone told me how I could revert to my former settings. Your help would be mcuh appreciated. Thanks in advance! 117.194.225.94 (talk) 19:57, 6 November 2009 (UTC)


 * Try this. -- LarryMac  | Talk  20:50, 6 November 2009 (UTC)

Thanks a bunch. That worked beautifully!! 117.194.224.97 (talk) 17:37, 7 November 2009 (UTC)

Installing Windows on another computer
I have an old WinXp computer, computer A, that has a certificate of authenticity and a Windows installation disc. I have another better faster computer, computer B, then has neither of these and currently has Windows 2000 on it. I would like to instal Linux on computer A, and instal WinXp on computer B using the certificate of authenticity and the install disc from computer A. Is this going to create any problems please? 92.26.20.84 (talk) 20:38, 6 November 2009 (UTC)


 * I believe that technically, it will work; but your scheme may violate the license agreement for your copy of Windows XP. I believe some OEM copies of Windows are licensed for use only on the computer that the disc was bundled with.  Comet Tuttle (talk) 20:47, 6 November 2009 (UTC)
 * It should work, although as said above some Windows are restricted to certain computers, but this usually only applies to the brand name rather than specific model numbers (ie a compaq disk will work on any compaq computer) —Preceding unsigned comment added by 82.43.88.201 (talk) 22:39, 6 November 2009 (UTC)

Actually I've just bought a Dell reinstalation disk for XP as my non-Dell computer did not have one. And it does not have a certificate of authenticity but just a product key. The product key has been verified by Microsoft. In that scenario, would there be any technical problems doing the above? Or simply using the Dell disk if required for repairs, which is why I bought it? And as a hypothetical case, not something I'm going to do, what's to stop me repeating this over a number of computers? Would Microsoft really be able to detect when two different computers with the same product key do their online software updates? 92.29.76.111 (talk) 13:15, 7 November 2009 (UTC)


 * Yes, they would be able to do that. More recent software from MS seems to require that you go online to register your computer/OS combo, so they would know if you had more than one.  You might want to call MS, as I think what you are trying to do is actually entirely legal, and they will help you to unregister the first computer and register the new one.  If not, then they won't help you, but you don't have to worry about black helicopters either (too much bad PR, apparently :-) ).  StuRat (talk) 15:40, 7 November 2009 (UTC)

unLZ-GBA
I tried to add this image to my Pokémon Ruby rom using unLZ-GBA, yet I get this error message:
 * Error: Image is not Indexed

How do I fix this and add the image to my rom? --75.50.49.24 (talk) 21:11, 6 November 2009 (UTC)

Video Either Too Big Or Too Little
I made a video today of a game I was playing. I used Fraps (free version) and took 10 videos of 30 seconds each. Each of these videos was over 100MB big for some reason - meaning that 5 minutes of video was around 1GB. When I used Muvee AutoProducer to put them together and add music (5MB), the finished version ended up as 148MB. Somehow, these numbers don't add up. Can anyone explain to me what has happened? --KageTora - SPQW - (影虎) (talk) 21:31, 6 November 2009 (UTC)


 * It has to do with the compression and formatting of the video itself. Different video formats give drastically different results. I don't know about the software programs you mentioned, but it is common for screen capture apps to use formats that are uncompressed or very lightly compressed (like Animation codec), which are huge files. When you convert them into another codec, like MP4, you will get huge savings in file size (albeit with some loss in quality if the codec is lossy). --Mr.98 (talk) 21:37, 6 November 2009 (UTC)


 * Right, but Fraps outputted in .avi, and I chose .avi as the output option in MAP, too. --KageTora - SPQW - (影虎) (talk) 23:55, 6 November 2009 (UTC)


 * AVI is just a container format, it doesn't tell you what the codec is. Different AVI files can have different codecs (like MP4, DivX, etc.). The codec and its settings are going to determine the file size, not the container. To find out what the codec is, you should be able to open it in your video-watching program (like Windows Media Player) and find out what the differences between the files are. (I don't know WMP, but in Quicktime, there is a "Movie Inspector" that tells you the info.) --Mr.98 (talk) 00:29, 7 November 2009 (UTC)

Need help overlaying an image
Hello. I'm an admin here on teh Wiki, but when it comes to image manipulation, I am strictly bush-league. Farm league. Possibly tee-ball. Anyway, would anyone be willing to help me out with this? I tried downloading Gimp but I think I'm past the sweet spot age for understanding this stuff. I could email you the photos with a description of what I need. Should be really easy for anyone familiar with gimp or photoshop. Tan  &#124;   39  22:57, 6 November 2009 (UTC)
 * I can help. Just post what you'd like and I'll get on it. In the future, you can ask the WP:Graphics lab -- penubag  (talk) 00:33, 7 November 2009 (UTC)

Cell phone question
Is it possible on Verizon Wireless to block numbers so that they can't call you? If it helps, I have a Samsung Gleam (SCH-u700). Nick4404 yada yada yada What have I done? 23:11, 6 November 2009 (UTC)


 * Yes! Verizon Wireless offers the ability to block up to five designated numbers from calling you. For more information, please visit link. There are certain limitations to this service. I recommend that you read the page above in its entirety. If it does not solve your problem, please feel free to comment below. Sincerely,


 * Kushal (talk) 00:14, 7 November 2009 (UTC)

Named nested references
I have a problem with nested references/notes to which I would like to assign a name in order to reuse them. Any help appreciated. bamse (talk) 23:59, 6 November 2009 (UTC)


 * For those who are confused by this Q, like I was, it appears to be about wiki markup. StuRat (talk) 15:32, 7 November 2009 (UTC)


 * Never mind, I found my mistake (forgotten "group=..."). Sorry for the confusion.bamse (talk) 16:14, 7 November 2009 (UTC)