Wikipedia:Reference desk/Archives/Computing/2007 November 21

Welcome to the Wikipedia Computing Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

November 21

information technology in 21st century

can anyone please tell about information technology in 21st century?220.224.121.1 (talk) 05:01, 21 November 2007 (UTC)kaki

Do your own homework. The reference desk will not give you answers for your homework, although we will try to help you out if there is a specific part of your homework you do not understand. Make an effort to show that you have tried solving it first. Asking for an 'essay' as an answer on the Science Desk is a bit of a give away. I will leave the question in case any kind hearted soul wants to point you in the right direction, but seriously, Do your own homework. Lanfear's Bane | t 10:58, 21 November 2007 (UTC)

Well, I'm a kind hearted soul (hmm, blushes) but I'm bu**ered if I'm going to do your homework without a bit of effort on your part. Have you done any searches? you're here posting this question so you have some handle on the technology. Now just take another step forward and use the IT that you're asking about. Richard Avery (talk) 15:55, 21 November 2007 (UTC)

A also am ma**arined if I'm going to help him unless he learns to ask properly. (Is this a british english thing?) --ffroth 01:17, 22 November 2007 (UTC)

Here's a big hint: In the 21st century, information technology will rise up and destroy all human societies, replacing them with nothing but more information technology; it will be IT all the way up! Just keep going on that track and I'm sure the teacher will give you an A! --24.147.86.187 (talk) 17:05, 21 November 2007 (UTC)

It is also a very vague (not to mention poorly worded) question. As a starting point, see the Wikipedia link on Information Technology, if you need anything more specific, we can help if you clearly explain what you are looking for but we will not do your homework for you, getting someone else to do it doesn't benefit you as you don't learn anything. GaryReggae (talk) 20:14, 21 November 2007 (UTC)

uninstall

i have 3 os in my pc.how do i uninstall vista.its a disgrace to technology and a waste of precious space.i dont have the cd. 2.am using suse linux dektop enterprise.am having trouble using it.am learning programming and am not sure how linux will asist.are the tutorials in linux? 3.when i boot on xp and open my computer,i see two cd drives yet i only have one.av checked the cables but its not going away.is it a virus.and i always receve a message prompting me that i have files waiting to be burned onto that drive —Preceding unsigned comment added by 212.49.92.115 (talk) 11:17, 21 November 2007 (UTC)

• If you're sure you don't want anything on the hard drive partition which Vista is installed on, you can reformat the disk. There's plenty of tools to do this (QtParted/GParted for example).
• There are quite a few tutorials for Linux, but Linux is big and covers many software programs. Most questions can be answered by Google, any others could be answered by posting on a forum (like this reference desk, or this one). Also look around your local area for a Linux users' group who can help you. Linux has many programming tools - which one is best really depends what programing language you want to use.
• With your CD problem - if it's just a cosmetic problem, then leave it be. If you want to change it, the issue will probably be shown by going to control panel > system > click device manager button. Check the cd drives listed don't have yellow exclamation marks next to them - if they do, double click them and follow the advise shown (probably re-installing drivers).

--h2g2bob (talk) 23:08, 21 November 2007 (UTC)

In Linux, you can obliterate Vista by reformatting it's disk partition. The 'fdisk' program (run as root) will allow you view the partitions on that drive - and to change the partition ID from whatever Vista uses to (say) 0x83 - which is a Linux partition - then write that out to the hard drive. Then use 'mkfs' (again, as root) to make a file-system on that partition (this is "formatting" the disk in normal terms). Finally, add your new partition into /etc/fstab so that Linux will mount it (either on commmand or on startup). But PLEASE be very, very careful. Treat 'fdisk' and 'mkfs' with the kind of care you'd take with a loaded gun that's pointed at your foot! Either program can annihilate your entire system quite easily. So be REALLY sure you have the correct partition name/number and all of that stuff before you proceed - make sure that every file you care about is backed up before you start. Trust me - I've seen some pretty spectacular screwups with this pair of programs! SteveBaker (talk) 07:37, 22 November 2007 (UTC)

linux 2

what is the best video player for linux?what site can i use for cool linux softwares —Preceding unsigned comment added by 212.49.92.115 (talk) 11:39, 21 November 2007 (UTC)

Sourceforge.net and Freshmeat.net are both good for finding Linux programs.--droptone (talk) 13:36, 21 November 2007 (UTC)

VLC? There are licensing issues, so you probably won't find it in a Fedora/Debian/BSD repository --ffroth 21:00, 21 November 2007 (UTC)

See Comparison of media players and look at the ones that support Linux under operating system support. Usually the repository of your distribution is a good place to look for software. --Spoon! (talk) 05:14, 22 November 2007 (UTC)

CCCP recommends MPlayer for Linux. — Shinhan < talk > 11:05, 24 November 2007 (UTC)

sql

sqlبازگشتی —Preceding unsigned comment added by 80.71.125.241 (talk) 13:00, 21 November 2007 (UTC)

Does SQL help? or ar:لغة الاستعلامات البنيوية? Graeme Bartlett (talk) 21:09, 21 November 2007 (UTC)

Linux keyboard problems

Hi! After running the following linux command: # dpkg-reconfigure xserver-xorg configuration and the subsequent configuration process I'm having problems with the keys that have a third character, for example, pressing AltGr+7 will not make the braces appear (Portuguese layout), which is a bit annoying for someone trying to program. What can I do? Also, while trying to install the audio device drivers, the graphic mode isn't running immediately after boot, instead, I must type $ startx. And I still don't have sound. How can I solve these problems? I'm a total linux disaster. Thanks! 217.129.241.186 (talk) 15:18, 21 November 2007 (UTC)

Hi, dpkg-reconfigure locales might solve the braces. You will need to specify that you're using a Poruguese layout. To boot into X, the easiest way is to install an X display manager. If you use GNOME, run apt-get install gdm. If you run KDE, run apt-get install kdm. --Kjoonlee 22:58, 21 November 2007 (UTC)

I'll try that, thanks! But I already have a X manager, I use ubuntu, it just doesn't start after boot. I have to type startx. 217.129.241.186 (talk) 23:07, 21 November 2007 (UTC)

There should be an option in dpkg-reconfigure xserver-xorg asking about keyboard layout. You should just be able to type "pt" in the box. (example: here)

Or you could edit /etc/xorg.conf. As root, create a backup copy of xorg.conf. Edit the file, changing the appropriate line to Option "XkbLayout" "pt" There are more variants here you could try.

KDE also does some keyboard stuff in kcontrol, which might be worth looking at. --h2g2bob (talk) 23:27, 21 November 2007 (UTC)

If you don't know how to make X auto start you really should be using one of the distributions instead of trying to build your own (if that's what you're doing). --antilived^{T | C | G} 06:43, 22 November 2007 (UTC)

I'm actually only programming the support for a basic file system. I'm not a computer science student, I study electronics & telecommunications.

217.129.241.186 (talk) 00:03, 23 November 2007 (UTC)

Different sizes

What accounts for the difference between the full number of bytes and the amount indicated before the parenthesis in MB or GB and between the "size" and "size on disk" when clicking on properties of a folder in Windows Explorer? For example:

Location: C:\Here\and\there

Size: 2,21 GB (2.235.887.280 bytes)

Size on disk: 2,40 GB (2.581.848.064 bytes)

Contains 3.560 Files, 322 Folders

Thank you. Keria (talk) 16:47, 21 November 2007 (UTC)

It has to do with how files are stored on a disk. The size represents the actual byte size of the files, whereas "size on disk" refers to how many clusters it takes up. Sometimes files take up more clusters than their physical byte size, or, in other words, don't completely fill up the space allotted to them. Defragmenting your drive can help reduce this a bit if it is extreme (it forces files to more efficiently use the clusters) but some degree of this is going to be inherently there in most file systems. It's kind of like saying that every file must be broken into chunks of 8 bytes (this is an arbitrarily and randomly chosen value here), but most files are not going to be perfectly divisible into chunks of 8 bytes, so the last chunk might only contain 1 byte or 2 byte, but is taking up an entire 8 byte chunk of the drive on the disk. At least, I think that's what it is like—someone correct me if I've got it wrong! --24.147.86.187 (talk) 17:02, 21 November 2007 (UTC)

So if I were to copy these files on a hardrive mp3 player which number should I take into account? Keria (talk) 17:48, 21 November 2007 (UTC)

You will need to take into account the first number (size), as well as how free space is distributed on your mp3 player. If your player is originally empty, the files are going to be copied to it pretty much in order, thus minimizing the amount of slack space. If you already have files on your mp3 player, and if you frequently delete some files and replace them with different files, then the free space on your mp3 player is probably fragmented, so the slack space problem is going to be more pronounced.

In practice, however, the effect is not going to be very noticeable, especially for mp3 files, which are fairly large in size. This only becomes a problem when you need to copy a great number of very small files. Hope this helps.—Ëzhiki (Igels Hérissonovich Ïzhakoff-Amursky) • (yo?); 17:59, 21 November 2007 (UTC)

Fragmentation is part of it, but there's also filesystem overhead --ffroth 01:13, 22 November 2007 (UTC)

How can fragmentation have anything to do with cluster usage? Sorry but a file does not extend to another fragment until its first cluster block is fully used. You don't find files that have 3/4 used a cluster and 3/4 another one etc. De-fragmenting won't reduce the amount of info that is in clusters but not being used. The only way to improve that is to turn down the cluster size.--Dacium (talk) 01:50, 22 November 2007 (UTC)

• Why are do the numbers in bytes look different than the numbers in MB and GB?

Normal metric prefixes follow the pattern of 1 km = 1000 m; 1 Mm = 1000² m; 1 Gm = 1000³ m, and so on. When converting to a different prefix, you only have to move the decimal point but the significant digits stay the same or round up. (5678 m = 5.68 km)

Bytes however, don't follow the same rules. 1 KB = 1024 bytes; 1 MB = 1024² bytes; 1 GB = 1024³ bytes, and so on. When converting to a different prefix, the significant digits change. (5678 bytes = 5.54 KB) --Bavi H (talk) 10:07, 22 November 2007 (UTC)

• What's the difference between file size and size on disk?

There's a lot of correct and incorrect information here, so I'd like to try to clarify.

Although files have sizes in bytes, the space on a hard disk is divided into clusters. A cluster is a certain number of bytes in size, and can be different from one hard disk to the next, depending on how it is formatted. The way a hard disk is organized, a cluster is the smallest thing that can be used to store file data. When storing files, the disk always fills up a cluster before using another one. If a file size isn't an exact multiple of the cluster size, then the last cluster will have some left over space that's not part of the file, but still accounts for the "size on disk" number.

To find out the cluster size on your hard disk, just open Notepad, type in exactly one character, then save the file. If you look at the properties of that file in Explorer, you will see that the file size is 1 byte, but the size on disk will be the size of one cluster. On my hard disk, the cluster size is 4.00 KB (4096 bytes). So on my hard disk, any files from 1 to 4096 bytes in size will fit into one cluster and use 4096 bytes on the disk. Any files from 4097 to 8192 bytes in size will fit into two clusters and use 8192 bytes on the disk. And so on.

When you copy files from one disk to another disk with a different cluster size, you'd have to do calculations to figure out what the size on disk would be on the new disk. Generally, it's not worth bothering about becuase it's not much more than the total file size. So you usually can just pay attention to the file size when copying files. You asked about copying files to your MP3 player as an example. I don't have an MP3 player, but the Music folder on my hard disk contains 783 MP3 files (46 hours 20 minutes) and uses 3.08 GB. The difference between the total size on disk and total file size is only 1.47 MB, which is very roughly equivalent to the size of a 1 minute 30 second MP3 file of average quality.

When you are creating files on a disk, you only have to be concerned about wasting space if there are lots of small files that don't fill up very much of their last cluster. The most extreme example is if I had a lot of 1 byte files for some reason. Each file would use one cluster on the disk and so there'd be a lot of space on the disk being used up without storing any useful info. The next most extreme example is if I had a lot of 4097 byte files (the size of one cluster on my hard disk plus one byte). Each one of these files would use up two clusters each, but the second cluster would be mostly empty, so nearly half of the space the files use on disk wouldn't be storing anything useful. In general, most files will use more than 1 byte of their last cluster. And as your files get larger, the amount of space left over in the last cluster is less and less of something to worry about. --Bavi H (talk) 10:07, 22 November 2007 (UTC)

• Although it wasn't in your question, others have brought up fragmentation.

Fragmentation has nothing to do with how much space is used on the disk. A fragmented file just means its clusters aren't in order next to each other on the disk. Defragmenting a file doesn't change how much space is used on the disk, it just puts the clusters in order next to each other on the disk, so it can be read faster. Defragmenting a drive doesn't change the way clusters are used: When writing a file, a disk always fills a cluster before using another one. The distribution of free space doesn't affect how much space is used: The same number of free clusters are used during the writing of a certain size file no matter where the free clusters are located on the disk. --Bavi H (talk) 10:07, 22 November 2007 (UTC)

Gtype and Sample Triggering Software

hello, I'm a training sound engineer. I've known about many theatre sound designers triggering sound effects from a Akai Sampler and PC using Gtype software. However, i run a mac platform. Any suggestions for ways to trigger sounds from a Mac using a MIDI or USB interface?

I don't really want to run bootcamp.

86.139.90.55 (talk) 18:58, 21 November 2007 (UTC)

I don't know about sampling software at all, but I will say that it is extremely easy to run a virtualizer on OS X with an Intel processor. I run Parallels Desktop for a few things I do that only run on Windows, and it is a complete snap. --24.147.86.187 (talk) 21:39, 21 November 2007 (UTC)

coldfusion applications -- disable server-side caching per-page

If there is anyone on here who knows about ColdFusion, I need a way to disable server (and client) side caching of specific pages, without turning off caching entirely on the entire server. Is there a way to do this in a cf tag?

Alternatively, if anyone knows a better forum to ask this question please feel free to slap up a link. Gracias. NoClutter (talk) 19:09, 21 November 2007 (UTC)

I don't know CF specifically, but the general way to prevent the client from caching is to set a cache-control "nocache" line - see this -- Finlay McWalter | Talk 23:07, 21 November 2007 (UTC)