Revision as of 14:09, 7 November 2007

WP:RD/C C #eee #f5f5f5 #eee #aaa #aaa #aaa #00f #00f #000 #00f computing Misplaced Pages:Reference desk/Computing Computing WP:RD/C

November 1

Movie Freezes with Laptop Movement

I've got a pretty new, really nice Thinkpad T60p widescreen that doesn't seem to have any major problems (any more.) It's super fast. It doesn't freeze or anything. The only problem I've been noticing lately, and an annoying one, is that when I'm playing movies (in any player - VLC, WMP, Realplayer) if I agitate the computer more than a bit (pick it up, lift part of it up more than about 5 degrees off the ground), the video (and sound) will temporarily stop, and then restart a couple seconds later. This is annoying, because I like to watch movies in bed with my laptop on my chest, and if I shuffle around any, or reach to get something, or scoot back a bit, the videos stops for a bit and skips a couple seconds forward. What's the deal with this? I haven't been treating my computer particularly roughly. Could it be something I could correct, or should I have this checked by a professional, or do I have to send it back to Lenovo to get something physical changed? Thanks so much, 140.247.40.254 04:45, 1 November 2007 (UTC) Oh yeah. This is for both DVDs and downloaded videos. And one time I was showing a DVD (possibly a bit scratched) to a couple people, and it would routinely stop for 5 or so seconds every 1-2 minutes, even when it wasn't moved at all. Don't know if that's related. Any suggestions? Is this a videocard thing? Has something been banged up inside the computer? 140.247.40.254 04:47, 1 November 2007 (UTC)

Is it a DVD? If it's a DVD you're jostling the reader, which depends on some stability to work properly -- that's probably why it's freezing. If it's not a DVD, I have no clue. Gscshoyru 04:48, 1 November 2007 (UTC)

This may sound stupid but I will ask it anyways.

You mentioned the word "lately". Did you not have this problem under the *exact* circumstances before? Can you recreate the skipping situation at will? Do you have a video clip on your computer (preferably on your hard disk drive) that you can play without using your optical disk drive?

Thank you for answering. I hope we will come up with some idea soon. Regards, --Kushal 05:42, 1 November 2007 (UTC)

Yeah. Right before I posted I tried viewing a couple videos on my hard drive (2 different ones) in several different players, and moving the computer around froze them consistently. I think this has been an issue for about as long as I have been watching movies on this (a couple months. I've had the computer since the beginning of this school year.) Also, I think it's tangentially important that music does NOT similarly freeze when I move the computer, although when the video freezes, its soundtrack does as well. I can't figure out what this could be. Which isn't to say that if I could I would have any idea what to do about it. 140.247.40.254 05:51, 1 November 2007 (UTC)

I've got an idea. Newer Thinkpads (especially the highend ones) sense movement and cease movement of the hard drive's platter and some other things to avoid any possible damages from falling, like off a desk. Perhaps its sensor is believing incorrectly you are dropping it. -Wooty   08:36, 1 November 2007 (UTC)

You've got a point, Wooty! Does anyone know if Lenovo has said anything about it yet? Or is it an isolated incicent? --Kushal 12:55, 1 November 2007 (UTC) If this is not an isolated case, Lenovo is probably all ears about it because the motion sensor is one of the most touted features on a thinkPad. To the OP, please try notifying the manufacturer about your situation. Thanks, --Kushal 13:46, 1 November 2007 (UTC)

This isn't a problem, this is a feature. It's not streaming off the DVD to the screen, it goes though a sizable buffer on the hard drive. The Active Protection System locks the read head when there's jostling to keep it from being damaged, so the hard drive is unavailable and requests for file I/O aren't filled until everything is unlocked a second or so later. I highly encourage you to leave this feature on, it'll save your hard drive years of life, but you can always go to Control Panel -> Active Protection System and turn down the sensitivity. You can use the preview pane there to see the physical orientation of your laptop and whether your current settings are causing the hard drive to lock in different positions. --ffroth 18:00, 1 November 2007 (UTC)

Thanks for all the diagnoses, but does anybody have any suggestions that wont take "years of life" off of my hard drive? Is the sensor over sensitive? Can I do anything about this? Should I ask some computer guy to help me do something about it? Or is the problem unfixable unless I take the aforementioned drastic actions? I don't know all that much about computers, so any really complex instructions might go over my head, but really anything's appreciated. Thanks so much for all your help. 140.247.41.134 02:41, 2 November 2007 (UTC)

Yeah I just said how to turn down the sensitivity in the above comment ^^^^^ --ffroth 05:46, 4 November 2007 (UTC)

C++

Are there any non dot net libraries for making simple get/post requests in C++. --Chris  G  09:17, 1 November 2007 (UTC)

• See Boost and libcurl. --Sean 10:50, 1 November 2007 (UTC)

Tutorials on making gnome-panel applets?

I want to make an applet to get my graphics card temperature and display it on my gnome-panel (and also as a little exercise). However I can't really find any tutorials on Google. Does anyone know any good tutorials for this, preferably for python? --antilived 10:04, 1 November 2007 (UTC)

• On my system some simple examples live under /usr/share/doc/python-gnome2-desktop/examples/applet/ --Sean 10:56, 1 November 2007 (UTC)

Python newbie question

Also, how do you assign the stdout of a programme executed through os.system() into a variable? var = os.system() only assigns the exit state of the programme. --antilived 10:09, 1 November 2007 (UTC)

Try os.popen2() -- JSBillings 10:44, 1 November 2007 (UTC)

How do you use that? Documentations say it creates a file object but how do you read the stdout? This doesn't work (just using ls as an example)

>>> ls = os.popen2('ls')
>>> ls.child_stdout
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'tuple' object has no attribute 'child_stdout'
>>> ls.stdout
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'tuple' object has no attribute 'stdout'

I'm still quite new to python so maybe there's something very fundamental that I've done wrong? Thanks. --antilived 10:33, 2 November 2007 (UTC)

• If you do this:

>>> import os
>>> os.popen2('ls')
    (<open file '<fdopen>', mode 'w' at 0xb7d09260>,
     <open file '<fdopen>', mode 'r' at 0xb7d09ec0>)

you can see that os.popen2() returns a tuple containing two file objects: the first one you can write to ('w'), and the second you can read from ('r'). We can keep references to those file objects like this:

>>> (to_child, from_child) = os.popen2('ls')

See the doco for file objects for how to access them. The easiest way is as an iterator:

>>> for line in from_child:
...     print line

--Sean 15:03, 2 November 2007 (UTC)

So there's nothing nice and simple like bash's

temp=$(nvclock -T | grep "GPU" | sed "s///g")

and instead you have to go through the whole file object? This works and returns it as a float but do I have to somehow close the file object is well?

(to_child, from_child) = os.popen2('nvclock -T | grep "GPU" | sed "s///g"')
temp = float(from_child.read())

--antilived 00:05, 3 November 2007 (UTC)

• No, when the file object goes out of scope, it will be cleaned up automagically. --Sean 02:06, 3 November 2007 (UTC)

OK thanks. --antilived 02:11, 3 November 2007 (UTC)

• FYI, here it is without grep or sed. I don't have nvclock, so I've faked it. --Sean 20:52, 3 November 2007 (UTC)

import os
import re
(to_child, from_child) = os.popen2('echo first line; echo GPU temp: 98.6; echo last line')
for line in from_child:
   match = re.match(r'GPU.*?(\d+\.\d+)', line)
   if match:
       temp = float(match.group(1))
       print "Temperature is %f" % temp

Is there any way to only select a specific line of the output so the whole grepping GPU step can be removed? The output of nvclock -T goes something like

robin@ubuntu:~$ nvclock -T
nVidia Geforce 6600/GT
=> GPU temperature: 67C
=> Board temperature: 47C

--antilived 23:40, 3 November 2007 (UTC)

• The above does exactly that, since it needs "GPU" and then a float. I was trying to demonstrate that with the three-line echo output. The nvclock output is a little different to what I thought (no decimal). If the line is as you marked it, this will do for the regular expression:

r'GPU temperature:\s*(\d+)C'

If it might have a decimal, this will work:

r'GPU temperature:\s*(\d+(\.\d+)?)C'

--Sean 00:42, 4 November 2007 (UTC)

Variables in Ruby

Let's say I declare:

myVar = 3

Then, later, by accident I declare:

myVer = 6

In a familiar language like C, the compiler would basically say "myVer is undeclared!" and I would notice the error. But in Ruby, wouldn't it declare a new variable myVer and leave myVar equal to 3? This is not a criticism, I'm just curious as to whether this can be a serious problem or something that you just get used to and learn to check when a bug occurs.

Consequently, are there any free / open-source Ruby IDEs that provide lists of variables / methods within your code? —Preceding unsigned comment added by 91.84.143.82 (talk) 11:40, 1 November 2007 (UTC)

I don't know Ruby, but in Perl the equivalent problem is solved by enabling "strict mode", which forces you to declare your variables the first time you use them, by prefixing them with the keywords "my" (for local variables) or "our" (for global ones). The compiler will also (optionally) warn you if it sees two such declarations for the same variable within the same scope. Of course, you can still get similar problems in strict mode e.g. with hash keys — you set $someHash{"example"} and then try to access $someHash{"exmple"} or something like that — since the compiler won't check those, but it still reduces the risk significantly. —Ilmari Karonen (talk) 13:08, 1 November 2007 (UTC)

Alas, there is no ruby equivalent of use strict. From looking at some discussions on the topic, it appears to be a misunderstanding of the benefits of use strict, thinking that it's simply a matter of providing a guard against inadvertently creating global variables. Ruby provides some minimal protection in that a variable can't be used without being set, so you're protected against doing something like

myVar = 3

myOtherVar = myVer

But you're not protected against a scenario where the wrong variable is changed. I was a bit disappointed to discover this as I had hoped that Ruby might be a good successor to Perl, but this is the sort of thing which shows that would-be Perl successors miss out on the reasons behind some of the design decisions in Perl (PHP does Ruby one worse by not only not having use strict, but also not having arrays). Donald Hosek 16:43, 1 November 2007 (UTC)

PHP does too have arrays. They're even more flexible than Ruby's, so it does Ruby one better! --ffroth 20:33, 1 November 2007 (UTC)

Identified by Email

There are several parts to this question. I appreciate your patience in helping me understand all that follows:

1.If I send an email on Misplaced Pages using the email button on someone's user pages, how am I identified on that email? Does the person to whom I send the email get my user name and the return email address or just my user name and a "reply" function that does not reveal my email address?

2.In general terms, is there any simple way a person receiving an email with a clear return email address can trace that address back to a real person? (I am assuming here that the return email address is not the person's name already.)

3. Can ArbCom trace an email to a real person who is using his own computer to send an email to the commitee, absent anything like a court order or a threat or something requiring third-party intervention? Thanks for your help. Bielle 16:12, 1 November 2007 (UTC)

See Misplaced Pages:Emailing users. Your username and email are sent to the recipient. --— Gadget850 (Ed)  - 18:21, 1 November 2007 (UTC)

That's the first question answered. Thank you, — Gadget850 (Ed)  - . Bielle 18:56, 1 November 2007 (UTC)

If you want to remain anonymous, just send it from a throwaway account, or use "Email this user" from a sockpuppet you've only used at your library or something. --ffroth 20:32, 1 November 2007 (UTC)

Thanks, ffroth but I am not looking to remain anonymous. I just want to know what it is possible to do. Bielle 02:22, 2 November 2007 (UTC)

Generally speaking You can see the IP address in an email header. From this you can get the ISP. They obviously know the address and the name of the person who pays the bill, but they wouldn't tell the arbitration committee! Theresa Knott | The otter sank 02:43, 2 November 2007 (UTC)

Hello and welcome....

I think that this question is "out there" but here goes anyways:

Is there a program that will give me the notes from an MP3 file OR a MIDI file in simple-to-understand format? I'm not a computer illerate, I know my way around my hardrive but let's say for example:

I take, oh, Chopin's: Prelude Op. 28/15 in D flat Major better known as "Raindrop" and download it form this source-

http://www.chopinmusic.net/includes/media/midi/28-15-prelude.mid

now, using a MIDI format like WIDI or a similar program that can take MP3 or MIDI and play or download and etc... I could make it into a saved MIDI file with my control to write and what-not. Is there a program that would change the MIDI format into readable notes like "D#" or "A#" or well...you get it, on my computer? It works on my digital piano, but just for the sake of simplicity of keeping it in one area...?

Thanks for your time!

-♥ECH3LON♥ 16:43, 1 November 2007 (UTC)

How about Finale Notepad. It's been a while since I used it, but it says it will import and export MIDI. By easy-to-understand format, I take it you mean actual musical notation. --Bennybp 16:52, 1 November 2007 (UTC)

BTW, it should just be one of those "click here to download" things, not the "sign up and recieve..." kinds of files, just plain OTC programs...like Wiki's link to download .ogg files. ♥ECH3LON♥ 16:58, 1 November 2007 (UTC)

You will never get a usable score out of an MP3 file. Especially not one with more than one instrument. Mid files are another issue though. It is often possible to get a usable score out of a .Mid file. I sometimes use Noteworthy Composer for this. It won't be perfect, and You may have to tweak the settings a little before you get a score that's as human-readable as you would like, but many MIDs can be converted into passably usable notation this way.

Of course, As for your specific example, The site you linked to also has sheet music. 69.95.50.15 17:04, 1 November 2007 (UTC)

help me find a venue to buy socket 478 motherboard please!?

Hi wiki's, my motherboard recently went dead and I would like to buy a new one of the same socket as opposed to upgrading the socket type which would require me to then also upgrade my cpu, ram, and video card. I have a socket 478 gigabyte 8IP900 motherbaord. I checked fry's and they don't carry them, I checked newegg and they only have 3 that are all horrible, and I searched my local craigslist to no avail....please help me find a good store/retailer/personal reference that can sell me a decent socket 478 motherboard. Thank you in advance. ````Brent —Preceding unsigned comment added by 64.238.49.65 (talk) 16:54, 1 November 2007 (UTC)

Try PriceWatch or PriceGrabber. --— Gadget850 (Ed)  - 17:32, 1 November 2007 (UTC)

And be sure to check ResellerRatings to see if the store you're looking at is reputable or not. --Carnildo 22:23, 1 November 2007 (UTC)

Classic code & magic constants

Can anyone help me understand what's going on in these 2 pieces of classic code? I understand a lot of each one but I lack the fitting-together that I know would just make my jaw drop :) User:SteveBaker, I'm looking at you: you've probably had experience with at least the first one.

float InvSqrt (float x){
   float xhalf = 0.5f*x;
   int i = *(int*)&x;
   i = 0x5f3759df - (i>>1);
   x = *(float*)&i;
   x = x*(1.5f - xhalf*x*x);
   return x;
}

I realize there's a lot of magic going into that famous constant, but I'm more interested in figuring out how this works at all. Specifically, how does it preserve the decimals of the float through the int cast? I'm sure the question reflects some fundamental misundertanding but that's what I'm trying to root out.

The 2nd code is more obscure- it counts the total number of bits set in an integer v.

unsigned int v; // count bits set in this (32-bit value)
unsigned int c; // store the total here
static const int S = {1, 2, 4, 8, 16}; // Magic Binary Numbers
static const int B;
B = 0x55555555; //01010101 01010101 01010101 01010101
B = 0x33333333; //00110011 00110011 00110011 00110011
B = 0x0F0F0F0F; //00001111 00001111 00001111 00001111
B = 0x00FF00FF; //00000000 11111111 00000000 11111111
B = 0x0000FFFF; //00000000 00000000 11111111 11111111
c = v - ((v >> 1) & B);
c = ((c >> S) & B) + (c & B);
c = ((c >> S) + c) & B;
c = ((c >> S) + c) & B;
c = ((c >> S) + c) & B;

The pattern in B is obvious but I can't wrap my mind around their magic :( --ffroth 17:54, 1 November 2007 (UTC)

I also don't fully understand the magic behind that magic number, so I'll leave that explanation to someone else, but it's important to note that what you have in example one is not an int cast. It's a int* cast being performed on an float*. The data is not modified by the cast itself. The cast only exists so that the next line can perform integer operations on data in memory that was intended to be interpreted as a float. 69.95.50.15 18:06, 1 November 2007 (UTC)

Oh ok, so it just takes the first part of the float (the mantissa I assume) as an int and works its magic on that, then casts back to float* to pick up the exponent again? --ffroth 18:16, 1 November 2007 (UTC)

No, I don't think so. An Int and a Float should be the same size. Ultimately, both the float and the int are stored as (lets say) four bytes of undifferentiated binary data. The compiler keeps track of whether you're pretending that binary data is an int or pretending that data is a float. Casting the float* to an int* lets change what you're pretending, and treat the entire four bytes of the float as though it were the entire four bytes of an int. I hope I'm explaining this clearly. Ultimately, this function (in example #1) is a trick involving the way floats are being represented as binary. 69.95.50.15 18:42, 1 November 2007 (UTC)

Found via google : A discussion of this clever hack. 69.95.50.15 19:05, 1 November 2007 (UTC)

Well, the second one is an ugly-ized version of the one on my web site! My version is MUCH prettier and very easy to remember when you want to impress chicks at a party:

  n = (n & 0x55555555) + ((n & 0xaaaaaaaa) >> 1);
  n = (n & 0x33333333) + ((n & 0xcccccccc) >> 2);
  n = (n & 0x0f0f0f0f) + ((n & 0xf0f0f0f0) >> 4);
  n = (n & 0x00ff00ff) + ((n & 0xff00ff00) >> 8);
  n = (n & 0x0000ffff) + ((n & 0xffff0000) >> 16);

(Sadly, far fewer women than you'd hope are actually impressed by this...especially at parties!)

The way this works is that the first statement adds every odd numbered bit to it's neighbour (an even numbered bit) and stores each result into a little 2 bit number. It's doing all 16 one-bit additions in parallel! Each of those 16 two bit numbers are packed into the space where the odd numbered bit and it's neighbour used to be. The second statement adds every alternate 2 bit number to it's neighbouring 2 bit number and stores the result as a 4 bit number - and now there are 8 four bit numbers packed together...the next adds 4 bit numbers and packs them into 8 bits, then the next adds 8 bit numbers and stores them in 16 bits...and the last statement of all adds up the two 16 bit numbers to give you the answer.

This is unspeakably cool - but sadly, I can't claim to have invented it (although - if you happen to be a female at a party, I may accidentally make it SEEM as if I did). SteveBaker 19:01, 1 November 2007 (UTC)

Gah, stop taunting me! I don't get it at all. What's with the shifts? You're not adding every odd numbered bit to its neighbor, you're adding every odd numbered bit to its neighbor divided in half(and fourths, and sixteenths, 256ths, and 65536ths)! (which doesn't even make sense- why would you shift a 16 bit number 16 bits?) Also .. hold on let me think I think I'm starting to get it O_O --ffroth 19:30, 1 November 2007 (UTC)

We have an article on this: Hamming weight --Spoon! 19:48, 1 November 2007 (UTC)

Why does your code have n ANDed with separate numbers in each line? Not that I understand it at all yet but shouldn't it be more like:

  n = (n & 0x55555555) + (n & (0x55555555 << 1));
  n = (n & 0x33333333) + (n & (0x33333333 << 2));
  n = (n & 0x0f0f0f0f) + (n & (0x0f0f0f0f << 4));
  n = (n & 0x00ff00ff) + (n & (0x00ff00ff << 8));
  n = (n & 0x0000ffff) + (n & (0x0000ffff << 16));

GaHHH!!! --ffroth 20:01, 1 November 2007 (UTC)

NO!!!! The version above is *NOT* the same as the one I provided and this version doesn't work!!!! SteveBaker 21:01, 1 November 2007 (UTC)

Wait, with this method you always end up with the starting "v". So it's obvious you actually have to shift one of the addends but why it actually works is still a mystery --ffroth 20:10, 1 November 2007 (UTC)

Aha, turns out yours is even an ugly-ized version of one that actually makes sense. How about this?

  n = (n & 0x55555555) + ((n >> 1) & 0x55555555);
  n = (n & 0x33333333) + ((n >> 2) & 0x33333333);
  n = (n & 0x0f0f0f0f) + ((n >> 4) & 0x0f0f0f0f);
  n = (n & 0x00ff00ff) + ((n >> 8) & 0x00ff00ff);
  n = (n & 0x0000ffff) + ((n >> 16) & 0x0000ffff);

Now it's starting to come together >_< --ffroth 20:16, 1 November 2007 (UTC)

Yeah - that works. I don't see how it's easier to understand - but whatever helps your brain! SteveBaker 21:01, 1 November 2007 (UTC)

Your skill in bit twiddling: +1. Your brain not being mash: -2. I finally get it, thanks. That last bit helped a lot, I would never have gotten it out of the original code, and probably not out of Steves --ffroth 20:29, 1 November 2007 (UTC)

Bit twiddling skills are important. The original version was ugly and inefficient. The five-line version is better and faster and much easier to grok.

So - what about this one?

  n = ((n >>  1) & 0x55555555) | ((n <<  1) & 0xaaaaaaaa) ;
  n = ((n >>  2) & 0x33333333) | ((n <<  2) & 0xcccccccc) ;
  n = ((n >>  4) & 0x0f0f0f0f) | ((n <<  4) & 0xf0f0f0f0) ;
  n = ((n >>  8) & 0x00ff00ff) | ((n <<  8) & 0xff00ff00) ;
  n = ((n >> 16) & 0x0000ffff) | ((n << 16) & 0xffff0000) ;

(It reverses the order of the bits in 'n' efficiently.) SteveBaker 21:01, 1 November 2007 (UTC)

In some programming languages (old-fashioned K&R C for example), you can swap the values of two variables in one statement like this:

 x ^= y ^= x ^= y ; 

('^' means 'XOR')...but it's not legal in more recent versions of C++ and ANSI C because there is now a ban on changing the value of a variable more than once in a single statement (bah!). I'm not sure about other languages.

SteveBaker 21:01, 1 November 2007 (UTC)

Yah, it's still possible with multiple statements

x^=y
y^=x
x^=y

We even have an article on it --ffroth 21:48, 1 November 2007 (UTC)

Oh - yes, sure - but it's not as much fun. In reality, both your way and mine will compile down to the same machine-code - and an old-fashioned "tmp=x;x=y;y=tmp;" is likely to be faster...but if you've ever had to program on a computer with only 32 bytes of RAM, you'll know where I'm coming from! SteveBaker 23:07, 1 November 2007 (UTC)

Isn't there some kind of added instruction set or something to IA32 that lets you actually "rename" the registers on a hardware level in supported processors so swapping values is just a matter of activating a different set of control lines? Any idea what I'm thinking of? --ffroth 04:49, 2 November 2007 (UTC)

On Pentium M and Core processors the FXCH instruction is implemented by register renaming and doesn't tie up any execution units. FXCH isn't a new instruction, though (it's been around since the 8087). -- BenRG 14:50, 2 November 2007 (UTC)

• Nerds who have enjoyed this thread should waddle quickly to the library and check out the magnificent Hacker's Delight, by Henry Warren. -- Sean/TotoBaggins —Preceding unsigned comment added by 198.85.228.129 (talk) 21:22, 1 November 2007 (UTC)

Gulp. Heavy breathing. You realize I'm going to have to buy this don't you? It'll ruin all of my plans to buy that $200 pc. --ffroth 21:48, 1 November 2007 (UTC)

This made me lawl hard. Barnes and Noble has it categorized as "Home > Books > Terrorism". --ffroth 20:46, 2 November 2007 (UTC)

I never did get around to explaining the first one:

 float InvSqrt (float x){
    float xhalf = 0.5f*x;     // Line 1
    int i = *(int*)&x;        // Line 2
    i = 0x5f3759df - (i>>1);  // Line 3
    x = *(float*)&i;          // Line 4
    x = x*(1.5f - xhalf*x*x); // Line 5
    return x;
 }

The easiest way to understand this is to look at line 5 first. The traditional way to do a 1/sqrt(x) is to use the Newton–Raphson method - in which you take a guess at the answer - then correct that guess by repeatedly calculating error terms and retrying. Line 5 is ONE iteration of that method. So the 'x' that comes out of line 4 is a guess for 1/sqrt() and line 5 fixes it up a little bit. Line 1 is obvious - and it's really just there to keep the original X lying around ready for step 5. Lines 2 and 4 are there merely to allow line 3 to operate on the individual bits of the floating point representation of the original number. So what the all-important line 3 does is to generate a guess for 1/sqrt(x) that line 5 will merely correct somewhat. So what the heck does line 3 do?

Think of line 3 as working in logarithms to base 2. If you look at the diagram, you'll see that the integer version of a POSITIVE IEEE float (you can't take 1/sqrt of negative numbers - so it's always positive) has the exponent of the number (which in IEEE math is at the top end of the 32 bit word) as a simple integer with the mantissa stuck in the lower order bits. So very roughly - the integer image of a positive IEEE float 'x' is approximately log₂(x). If that were true then (i>>1) simply halves the exponent and the minus sign in front of -(i>>1) is negating the result of that. Which is like taking the reciprocal of the square root of the original number x. The bigger mystery is this correction factor 0x5F3759F. The high order bits of that are there to correct for the fact that IEEE floating point doesn't literally store the exponent - it stores the exponent with some positive constant added to it to avoid the need to have a sign bit for the exponent - so the '5F' part is a correction for that. All of that messing around gets you a guess for 1/sqrt(x) that is within a factor of two of the exact answer - which after the correction factor applied by one step of Newton-Raphson gives you a reasonably good answer.

However, the lower order bits of this weird constant 0x5F3759F seem like they shouldn't matter much - after all, the shifting and negating of the mantissa as if it were a logarithm (when it's not) is all screwed up anyway...so why aren't the low order bits just all zeroes or something? Well, I believe (although I don't know for sure) that those low order bits were arrived at by trying every possible floating point number with this algorithm and seeing which value could be added to the result to minimise the worst case errors. I don't think it was ever calculated - I think someone wrote a program to figure out the best compromise over the entire number range. It significiantly improves the guess for some numbers - and (predictably) worsens it for others - but by writing a program to figure out the best compromise, you get better precision for the areas of the number range that would have had particularly bad answers - and worse precision for numbers that gave better results. In most applications, that's a good thing.

So, there you go. It's essentially a calculation on the log-to-base-2 of the number to guess at 1/sqrt(x) - then one iteration of a well known successive approximation algorithm. It's not rocket science - and it only LOOKS like black magic.

SteveBaker 23:52, 1 November 2007 (UTC)

So easy once someone just explains it! I can't wait for my copy of Hacker's Delight to arrive (yes I ordered it -_- no, not from amazon) --ffroth 04:43, 2 November 2007 (UTC)

Yeah - but beware. This 5 line chunk of code takes 5 long paragraphs of hard-to-read explanation to even give a rough idea of what it does - that's never a good sign. On a modern PC, InvSqrt is about 40% faster than 1.0f/sqrtf(x) - but you'd have to be pretty desperate to want to use it because it's inaccurate by around 0.2% in the worst parts of its range. There aren't many applications where you need to do 1/sqrt for any significant percentage of your total CPU time and a 40% saving of that small percentage - at a cost of 0.2% error rates just isn't worth it.

The thing to avoid at all costs is the temptation to use 1.0/InvSqrt(x) instead of sqrtf(x) - and on modern CPU's, the latter is typically faster as well as being more accurate. SteveBaker 18:09, 3 November 2007 (UTC)

It never even entered my mind to use 1/InvSqrt- but for applications where you need an InvSqrt like for vectors, you'd use it (and you're desperate for processing power because you're developing for 1990s hardware) --ffroth 05:42, 4 November 2007 (UTC)

But hm (if anyone's still reading this).. how about x*InvSqrt(x)? Still slower than sqrtf? Doubtlessly less accurate, but faster? --ffroth 23:23, 9 November 2007 (UTC)

Better late thanOK, better very late than never, but this thread (which is fairly impenetrable to me) is apparently very helpful, but it wins this last week's Ref Desk thread of the week award, mostly because of SteveBaker's comment "(Sadly, far fewer women than you'd hope are actually impressed by this...especially at parties!)". Anyway, well done, or should I say n = (n & 0x0f0f0f0f) + ((n >> 4) & 0x0f0f0f0f); --Dweller 14:18, 6 November 2007 (UTC)

Don't worry too much, Dweller. Even John Carmack didn't know what exactly he was doing:

 i  = * ( long * ) &y;  // evil floating point bit level hacking
 i  = 0x5f3759df - ( i >> 1 ); // what the fuck? 

-Wooty   10:46, 7 November 2007 (UTC)

NAT network bridging

I'm jealously eyeing this piece of crap to run as a server. I don't have an ethernet jack in my room (my laptop connects with wifi) so is there any daemon out there that can do this:

1. I connect to the wireless network with my laptop.
2. I connect my server box to my laptop with an ethernet crossover cable.
3. The server box thinks it's connected to a router or something because it recieves network information and is able to connect. It's important that this is transparent to the linux box because I don't think I can expect any weird-setup support from gOS.
4. My laptop translates (in the background) network requests from the ethernet jack to real network requests over wireless using NAT

So is there software out there that lets you do this? I've seen people pull off setups like connecting to the same network 4 times with different NICs for amazing bandwidth, so I figure there must be some kind of program that lets you mess with multiple network interfaces and forwarding --ffroth 18:36, 1 November 2007 (UTC)

And by NAT I guess I mean bridging, since I do want to be able to connect to the server from elsewhere within the (real) network --ffroth 18:43, 1 November 2007 (UTC)

If you're NATing, you're routing, not bridging. Software for this is common for linux I believe. There's probably something out there for windows too. Friday (talk) 18:46, 1 November 2007 (UTC)

Well yeah there's Internet Connection Sharing, but it's NAT-based and AFAIK there's no port forwarding option to get at the server from outside. I definitely want the server to use the laptop's network connection- not make a connection of its own, since the real network won't let me connect twice on the same user ID. That's NAT, right? So I need a port forwarding option, and something that can handle FTP's weirdness, neither of which ICS supports --ffroth 19:12, 1 November 2007 (UTC)

Oh wait, hold on ICS does support port forwarding. Verrry very promising, but I'd prefer to use something other than a "set up and forget" solution that actually affords a level of configurability --ffroth 19:19, 1 November 2007 (UTC)

Is there any NAT router software for windows? I see NAT32, but it costs money and doesn't work on vista anyway. --ffroth 21:24, 1 November 2007 (UTC)

Also, what category cable should I buy? Ethernet cables are dirt cheap from newegg, but the 7ft version only comes in cat6. It's backwards-compatible, right? Will my humble Intel Pro/1000 PL network card support cat-6? --ffroth 21:52, 1 November 2007 (UTC)

For much the same problem I use a ZyXEL G-470 ethernet-to-802.11 bridge. It bridges rather than NATing, and allows the ethernet devices behind it (a linux server, an antique media-extender, and an internet telephone box) to be on the network (and thus the internet) as if they were wired straight into the DSL box. It does WPA (which some similar products don't) and it's been absolutely as solid as a rock. -- Finlay McWalter | Talk 23:36, 1 November 2007 (UTC)

Why not buy a WiFi connection for your new server? It is pretty easy to get a WiFi expansion card (see here) or a WiFi USB adapter(see here) with prices starting from about $30 - just make sure you can get hold of the necessary Linux drivers for gOS (you might have to download these from the manufacturer's website). Astronaut 10:36, 2 November 2007 (UTC)

Because I can only connect one network interface to the school network at a time. Until you log in, every query to the network gateway is answered with a HTTP reply containing the HTML of the login page. After you use a browser to actually render that page and submit your login, the gateway functions normally. I don't think it'll let you log in 2 places at once. --ffroth 20:12, 2 November 2007 (UTC)

Yeah so login through your desktop, and use that as a NAT gateway for your laptop, that seems to make more sense if you want to use it as a server. YOu will have much more control with your linux box doing the routing. -- Diletante 21:02, 2 November 2007 (UTC)

Now that is a good idea. What would I use for this, iptables? --ffroth 00:01, 3 November 2007 (UTC)

Yeah. While you can compose the iptables rules yourself, to make things easy use a pre-made firewall script. Before I started using openwrt I used the projectfiles rc.firewall which you can find mirrored here, edit the rc.firewall script to suit your needs and make sure it runs at boot and you're good. I bet you can write a script in whatever language you are comfortable with to log in to the captive portal automatically too. -- Diletante 01:19, 3 November 2007 (UTC)

It only makes you log in once a week, so it's not enough of an issue to learn curl --ffroth 02:33, 3 November 2007 (UTC)

.NET question

As much as I hate it, my current job requires I work on .NET applications instead of Java Platform applications. Now, I have seen plenty of MSDN documentation of .NET technology, and they always give code samples both in VB.NET and C#. The difference between the code samples seems to be mostly syntactic, up to the point where one could write a parser to translate one language into another without even having access to the .NET library, or knowing how these languages are compiled. So what's the point in having two separate language implementations of the same library if they're this much alike? I understand the point of C#, but what I don't understand is why we need VB.NET if all it is is a more BASIC-looking way of writing C#. JIP | Talk 18:41, 1 November 2007 (UTC)

People who were already familiar with VB are seen as being less likely to be afraid of something called "VB.NET". Friday (talk) 18:43, 1 November 2007 (UTC)

Yeah, pretty much. A lot of (or most) people who use VB aren't 'programmers'. They use it to solve small problems for their business (or sometimes big problems, often with disasterous results, but that's another story...), but haven't really dabbled in programming beyond it. A lot of businesses use it like this. 130.179.28.118 20:26, 1 November 2007 (UTC)

VisualBasic.NET is seen by many as nothing more than a failed marketing ploy by Microsoft to fool people into thinking that they were not dropping all support for VisualBasic entirely, even though that's essentially what they did. (See e.g., [http://vb.mvps.org/vfred/Trust.asp VisualFred], Visual Fred, Visual Fred, Deprecation, Fear, uncertainty and doubt Dilbert). dr.ef.tymac 21:17, 3 November 2007 (UTC)

how can I...?

On a separate question: How (if i can) download videos from Youtube on to my computer (like a file)? I know that Google video has this quality but they don't have all of youtube's videos.

Any suggestions?

Thanks!

♥ECH3LON♥ 19:59, 1 November 2007 (UTC)

If you're using Firefox, then there are a number of add-ons that do this, such as this one for example. Algebraist 20:24, 1 November 2007 (UTC)

Or unplug, which is made by some wikipedian guy here. It manages to get some videos that others don't, since it's clever about what it does, and actually tries to adapt when it hits a page it's not programmed to download from. 130.179.28.118 20:31, 1 November 2007 (UTC)

This is a great tool. The demo version works fine, and it saves it to MPEG format, not the .flv format that is a pain. --Omnipotence407 22:24, 1 November 2007 (UTC)

But that's another transcoding, losing even more quality off the hopelessly mangled youtube format --ffroth 20:18, 2 November 2007 (UTC)

November 2

computer vb.net

what is a base class —Preceding unsigned comment added by 202.134.24.33 (talk) 00:16, 2 November 2007 (UTC)

I don't know VB but generally speaking, a 'class' is a structure with some member functions. Suppose you were writing a program to simulate animals on earth. You'd want classes for Lions and Tigers, Dogs, Wolves, Zebras, Horses,etc. Pretty soon you'd realise that lions and tigers would share a lot of code - and most of their data would be the same too. What you'd really like to do is to write a class called "class BigCat" - and have "class Lion" be derived from BigCat and class Tiger be derived from BigCat. In this case, 'BigCat' is the 'Base Class' from which Lions and Tigers are derived. However, we'd pretty soon discover that the base class of dog and wolf should be "class Canine". Now though you're going to start to notice things that BigCat and Canine have in common - so you derive both of them from 'class Carnivore' - and now THAT is the base class from which dogs, wolves, lions, tigers, canines and bigcats are all derived. In the end, you'll decide that EVERYTHING should be derived from class 'LivingThing' - from there "class Animal" and from that "class Mammal" and from that "class Carnivore" and so on down. But the 'base class' is at the "base" of this gigantic tree of classes. SteveBaker 00:32, 2 November 2007 (UTC)

Also see Inheritance (computer science). 130.237.57.80 11:48, 2 November 2007 (UTC)

Windows XP

Hiya, I have a Dell LAtitude CPx laptop, It has Windows XP, and a 10gb hard drive. 9gb are filled with viruses, spyware ect. I have bought Windows 2000 (the computer is from 2000, and so I presume it will work better with this on it) I wish to Format eveything and install windows 2000. XP does not have a dosprompt to enter and say format C:\ I am unable to make it boot from the CD ect ect ect. Can any one please tell me how to do this, as if I were a 2 year old, as I know next to nothing about computers, or could some one please provide a link to show me how to do this. Thank you very much. 12.191.136.2 12:17, 2 November 2007 (UTC)

XP certainly does have a DOS prompt. Click start/run then type CMD and hit enter. Can you explain what happens when you try to boot from CD? By the way, you might get more responses at the Computing ref desk, however be prepared also for people to tell you to use something other than Windows. --LarryMac | Talk 13:14, 2 November 2007 (UTC)

If I try to bbot from the cd, it seems that it will, but then just loads normal Windows XP as it did before, then takes 30 min to load into windows as usual. Further more, the XP dos prompt that I have found through the use of start-run-cmd cannot format any thing as it is still in windows. if that makes scence. Thanks

When you install XP, you have the option to format the harddrive. You cannot format the harddrive while IN windows. -- kainaw™ 13:25, 2 November 2007 (UTC)Ok, but I am unable to install 2000, as when in windows I open the D: drive, it says loading install wizard...operation has terminated to to error... I have many viruses. Please lead me trough it like a 2 year old thank you very much.

Have you tried going into the BIOS to change the boot order? When the computer starts to boot look for a phrase that reads something like " Hit delete to enter setup". It may not be delete, it may be one of the function keys or the enter key. Anyway when you see the phrase hit the key it states quickly! Then you should be able to change the boot order to cd first then harddrive. Theresa Knott | The otter sank 14:40, 2 November 2007 (UTC)

Dell Support Page with instructions on how to enter BIOS and change boot order. --LarryMac | Talk 14:46, 2 November 2007 (UTC)

CSS style for paragraph break size

Hi all,

I'm trying to change the height of my paragraph breaks. I have a bunch of text with paragraphs delineated with <p/> (not <p>...</p> — it would be a huge complication to change this, so it would be great if a solution didn't require this). In my p {...} tag in my CSS style sheet, I've tried setting the text size, the margin sizes and the padding, but none of this has worked.

If it because I'm using <p/> instead of <p>...</p>? Is it because my CSS renderer is only CSS 1.0 compliant? (It's a java-based renderer for laying out text in a java program).

Any ideas?

Thanks! — Sam 15:54, 2 November 2007 (UTC)

Yes. <p/> is an empty tag. The renderer sees no reason to display anything at all (regardless of padding, margins, etc...). Do a search&replace changing <p/> to </p><p> - then you'll only need to change the first and last tags for each series of paragraphs. -- kainaw™ 17:08, 2 November 2007 (UTC)

Kainaw I think you meant the reverse, and I corrected it in your comment. Also, why have empty p tags? Why not just increase the top and bottom margin? --antilived 21:53, 2 November 2007 (UTC)

No - I meant what I wrote. Currently, there is a <p/> tag between each paragraph. What you want between each paragraph is a "close the previous paragraph" followed by an "open the next paragraph". That is why you put the close first and the open second. Once done, all you need to do is ensure the very first paragraph has a single open tag and the very last paragraph ends with a single close tag. -- kainaw™ 21:56, 2 November 2007 (UTC)

I'm confused by what the OP meant with his <p/> tags. I think s/he's just using it for extra line breaks between normal p tags like <p>blah blah blah</p><p/><p>More Blah Blah</p>, so putting in empty p elements instead of <p/>would solve his/her problem; but then I might be wrong. --antilived 01:03, 3 November 2007 (UTC)

<P/> is correctly being ignored: We discourage authors from using empty P elements. User agents should ignore empty P elements. (W3C). --h2g2bob (talk) 03:58, 3 November 2007 (UTC)

I assume the OP means "Some text <p/> Some text <p/> Some text ...". If this is the case, and if this is the only time the 'p' tag is being used, a quick fix is to change the "height" css attribute of the 'p' tags, or the "min-height". Curiously though, on all three browsers I checked with this solution, all of the 'p's except for the first in the document correctly grow to the height specified, so you would need to make sure your code was of the form: "<p/> Some text <p/> Some text ..." -- DatRoot 12:08, 3 November 2007 (UTC)

The problem is that <p/> is exactly equivalent to <p></p> (with no text between them). Any attributes your CSS adds to <p> tags will only affect whatever is between the <p> and matching </p>...which in this case is nothing. So there is good justification for the browser ignoring <p/>. SteveBaker 05:22, 5 November 2007 (UTC)

"Word Attachment" Article

Hello all,

Does anybody know what happened to the Misplaced Pages article on "Word attachments"? —Preceding unsigned comment added by 129.132.168.26 (talk) 16:28, 2 November 2007 (UTC)

It got deleted on the 9th September. You can read the deletion discussion here. -- DatRoot 16:55, 2 November 2007 (UTC)

Additionally, if you created it, you can contest the deletion if you like. There's information at WP:WWMPD. -- DatRoot 17:02, 2 November 2007 (UTC)

2000 again

does windows 2000 come with Internet explorer and Outlook express already fitted or do I need to get these separatly? Thanks —Preceding unsigned comment added by 12.191.136.3 (talk) 16:32, 2 November 2007 (UTC)

Yes, but older versions. --— Gadget850 (Ed)  - 16:45, 2 November 2007 (UTC)

choosing the wright language

I want to know that which is the best language for network programming, is it python, perl or java,C#. I know C,C++,PHP. should i learn these languages? or are they enough? —Preceding unsigned comment added by Freaky guy (talk • contribs) 16:58, 2 November 2007 (UTC)

Most "network programming" is mere sending and receiving streams of characters. Technically, they are streams of bytes, but most applications are sending characters. So, any language in which you are comfortable handling IO streams is good. -- kainaw™ 17:05, 2 November 2007 (UTC)

• I think learning one (and one is adequate) of those languages would serve you well, as C and C++ are too cumbersome for casual programming, which is the best kind. PHP might be OK, but my experiences with it haven't been great. --Sean 17:53, 2 November 2007 (UTC)

Depends on your application. If you want to use it for web progamming, go for PHP. Is platform cross-compatibility a requirement? Java. I don't know what you mean by "network programming"- if you mean programming apps that work with networked computers, go with C++ and learn a lot of Windows API.. you'll have to use the Windows TCP/IP stack. --ffroth 20:15, 2 November 2007 (UTC)

I'd personally favour Java because it has pretty great libraries for handling streams and sockets (and everything else), and it's way easier to learn than C or C++. And you can make just as nice apps with it. --Oskar 01:08, 3 November 2007 (UTC)

Mouse

Is there any program that will allow you to make your mouse move faster when you are holding down a button and then go back to regular speed when you release that button? —Preceding unsigned comment added by 75.187.104.71 (talk) 20:02, 2 November 2007 (UTC)

November 3

this is about TCP ports

Thank you for the chance that you gave me to use this network for my concern, it is that i must have the TCP port 1999 openned on my computer in order to be able to see a Pico2000 remotely, but i have not even a clue about what is that port and how to open it, somebody could help me with this?

 Thank you so much people.-  —Preceding unsigned comment added by 190.31.204.110 (talk) 00:41, 3 November 2007 (UTC)

Do you have a router? Log into your router administration by typing in the IP address of your router into your browser, and use the port forwarding (sometimes known as "services") option to forward TCP 1999 to the IP address of the computer running Pico2000. To find these IP addresses: on the computer running Pico2000, go to Run and enter "cmd". At the DOS prompt type ipconfig and hit enter. The default gateway will be your router, and the local IP address will be the IP you want to forward to --ffroth 02:31, 3 November 2007 (UTC)

Uh, there are a few more details required. Many small/home networks use DHCP, in which each computer asks the router for it's TCP settings, and the router decides what local IP (among other things) each computer will use today. This means that a computer may have a different local IP tomorrow, so port-forwarding-to-this-IP won't work tomorrow. In order to make port forwarding stable, the computer running Pico2000 (whatever that is) must have a "static" IP. Once it has a local IP that won't change, the router can be set to forward all requests for port 1999 to that IP. -SandyJax 15:34, 5 November 2007 (UTC)

Automating the list creation process in Python

I've been wanting to write a small program which does the following:

1)User selects "Play new game"

2)Player selects from a menu 6 cards he sees on his opponent's hand

3)His choice goes to a list.

4)Player is asked if he wants to play again

5)If so, another 6 items are added to the list and so forth.

6)Once the player says he no longer wants to play, the list is sliced, 6 items at a time, as many times as the number of times the number of cards the player wrote down is evenly divisible by six and each set of 6 items gets a list of it's own, named, game_2, game_3,etc. We then use the .pop() function to delete all but the first six cards, or game_1.

7)Whenever the player wants to access a record of past games, he can do so and consult the aforementioned lists.

The problem is that I can only make the above work when I know the number of games the player will choose to play. That is, if I want to record, say, game_2 out of a 12 item list, I can only do this by defining game_2 = hand. How can I make the program slice the list 6 items at a time, as many times as the total number of items is evenly divided by 6, creating small 6 item lists, named game_2,game_3, etc, without having to define them myself? -- Ishikawa Minoru 01:10, 3 November 2007 (UTC)

Something like this?

cards = range(0, 52) # or a list of cards
game = 
while len(cards) >= 6:
   game.append( cards )
   cards = cards
print game
print cards

This splits a list into a list of lists containing 6 items; ie: , , ...]. --h2g2bob (talk) 03:50, 3 November 2007 (UTC)

which website for checking the following tracking number?

Dear Wikipedians:

A reference letter from my mentor was mailed out from North Carolina with the following tracking number:

R8175163889US

When I searched on USPS, the result returns that the tracking number is not found in their database. How do I track online where that letter has gone to now?

Thanks,

74.12.199.185 02:00, 3 November 2007 (UTC)

Maybe the mailman hasn't picked it up yet (in which case wait til tomorrow and check again), or maybe they used UPS or FedEx, or some other service? Astronaut 03:03, 3 November 2007 (UTC)

Don't forget DHL, that could be their shipper. Useight 04:53, 3 November 2007 (UTC)

FedEx also delivers express envelopes. Maybe that FedEx guy is knocking at yur door right now ... lol --Kushal 22:55, 4 November 2007 (UTC)Sorry I did not see Astronaut's reply. --Kushal 22:56, 4 November 2007 (UTC)

Signature Help

I know I should probably ask this on some other specified page, but it has to do with computer codes for signatures-

I am trying to find out how to find & have a variety of signatures. I have no idea where to go to find the "codes" for these things, nor do I know if anyone has "codes" for signatures, like mabye they just took some signature and "spiced it up". If there is any way possible for anyone to type the hard-to-read computer "codes" here then that would be just dandy! Or, you could just redirect me to someplace on[REDACTED] that is of help. Thank you! Zane Wolf 04:11, 3 November 2007 (UTC)

I don't think this is the right place to ask this...I would suggest trying the New contributors' help page. you'll probably get more of a response there anyways. Rabid9797 04:22, 3 November 2007 (UTC)

Uh just learn wikicode and css and a few html tags --ffroth 04:32, 3 November 2007 (UTC)

Uh ok, thank you for your help anyway. :) --Zane Wolf 04:36, 3 November 2007 (UTC)

DDR2 backwards compatibility

Is DDR2 SDRAM universally backwards compatible? I'm looking at a motherboard spec which says it has "Support for DDR2 800 MHz, or DDR2 667 MHz DIMMs", will it also support 400 MHz PC3200 PC2-3200? FiggyBee 04:34, 3 November 2007 (UTC)

I think it is, but I'm not positive. I'd try to purchase the exact type the motherboard recommends. I'd also recommend the brands Crucial or Corsair, but if you want bang for your buck, the next best is Ultra. Useight 04:52, 3 November 2007 (UTC)

I'd go for the faster RAM except I already have a gig and a half of Corsair PC3200 PC2-3200 that I'd like to reuse. For the record the board I'm looking at is the Intel DP35DPM. FiggyBee 04:57, 3 November 2007 (UTC)

Eh, actually the 667MHz PC2-5300 is so cheap I'm going to buy some anyway. Oh well, thanks. FiggyBee 06:02, 3 November 2007 (UTC)

To answer first question, yes that would work, the computer will clock it self down to the RAM speed, and on the last note, congrats on getting the faster RAM. Dureo 08:56, 3 November 2007 (UTC)

You people are so silly. DDR2 has a completely different amount of pins and structural layout than DDR1 - aka no, DDR1 will not work, and you're liable to break something. It's as backwards compatible as a vacuum tube jammed in my CPU socket. -Wooty   17:16, 3 November 2007 (UTC)

Yeah, I know that - I meant to say PC2-3200, not PC-3200. :) FiggyBee 23:11, 3 November 2007 (UTC)

Watermark on Output

I'm wanting to install a AVS Video editing software from CNET's download.com but it mentions on the page (http://www.download.com/AVS-Video-Editor/3000-13631_4-10721064.html) a limitation: "Watermark on output"

What does this exactly mean?

Thanks.206.45.166.216 08:38, 3 November 2007 (UTC)

I don't use that software, but I'd assume it means that it puts a watermark on anything you make unless you buy the full version, but I could be off. Dureo 08:54, 3 November 2007 (UTC)

Yes - the 'free' version puts a kind of translucent logo all over your video (a "watermark") - it makes the tool pretty much 100% useless unless you pony up the cash for the full version. —Preceding unsigned comment added by SteveBaker (talk • contribs) 17:33, 3 November 2007 (UTC)

And, in case you don't know, a watermark is a faint mark on paper that identifies the maker of the paper, or, in this case, the maker of the software. StuRat 17:35, 3 November 2007 (UTC)

Graphics cards

I want to upgrade the graphics card on my desktop computer. What kind of compatibility issues do I need to think about. How can I work out what type of graphics card it right for me? MHDIV ɪŋglɪʃnɜː(r)d(Suggestion?|wanna chat?) 16:02, 3 November 2007 (UTC)

I think it's just a matter of the kind of slot you have open on your motherboard. If you have a PCI-E x16 slot, that fits modern video cards. If you have 2 free slots, you can use dual cards to render the same display, with SLI or Crossfire (If you want this, make sure you buy cards specifically made for SLI/crossfire). Oh, there's the additional consideration of power- you need a very solid PSU to run newer cards (and a monster to run dual cards). Not only that but some of the beastier cards actually require a separate power connector- they trail a wire and you have to have a little power connector next to the PCI-E slot. --ffroth 17:02, 3 November 2007 (UTC)

You didn't say what OS you are running. If Linux, get a card with an nVidia chip - the drivers are much better than ATI on that platform. SteveBaker 17:31, 3 November 2007 (UTC)

Second that ... also consider a graphics card with nVidia chip if you think you might be migrating or dual-booting with GNU/Linux as one (or more) of the options. --Kushal 00:11, 4 November 2007 (UTC)

It's sort of a non-issue since linux is terrible for gaming anyway :) --ffroth 01:14, 4 November 2007 (UTC)

I don't mean to be rude but who is talking about video games? --Kushal 01:57, 4 November 2007 (UTC)

Yeah graphics card isn't only for gaming, you can use it for flashy, shiny effects is well! --antilived 05:27, 4 November 2007 (UTC)

Scanner Driver

Hi, can anyone please help me find a driver for a Primax Colorado USB 9600 scanner for Win XP please? DuncanHill 16:45, 3 November 2007 (UTC)

Apparently there is no such driver. -- ReyBrujo 16:55, 3 November 2007 (UTC)

However, there is a guide at the archive.org, check here. It may not work, though, as said in the page. -- ReyBrujo 17:01, 3 November 2007 (UTC)

Thanks, I'll give it a try. We got given an old scanner for our Scout Group, We've got a Win98 machine at the Scout Hut, but I thought I'd check the scanner out at home first. DuncanHill 18:20, 3 November 2007 (UTC)

In the past, I've found that scanners are not supported when jumping from Win95/98 to WinXP and then not supported when jumping from WinXP to WinVista. However, there are some companies that write new drivers for old scanners - for a charge. Our university has purchased a few of them because it was easier to pay for a new driver than to replace the scanner. Right now, we're looking into either purchasing replacements for all of our Lexmark scanners (which are not supported in Vista) or purchasing a new driver. -- kainaw™ 18:59, 3 November 2007 (UTC)

Just as a note, in case you haven't checked regularly, but there are new scanners that are available for quite cheap that can probably do anything you want to do with them. I got one at OfficeMax for less than $50 a few years ago and it has served me very well since then. I am not convinced it is worth spending a lot of time with old scanners since if no new drivers are available you have very little likelihood of success without spending more of your own time on it than it is worth monetarily. --24.147.86.187 16:02, 5 November 2007 (UTC)

It is true that it is better to replace cheap scanners with other cheap scanners. However, we have many scanners that cost over $5,000 and are not produced anymore. For example, we replaced our 1600DPI scanner with what we were told was a 1600DPI scanner. It turned out to be an 800DPI scanner that did a double-scan. So, we had to return it and pay for a driver. Now, I'm seeing tons of 300DPI and 600DPI scanners on the market (true-DPI, not advertised DPI). Those are simply not good enough for our work - even with double or triple scan. Also, good slide scanners are very hard to find. We need those to scan in X-Ray film. Newer scanners offer a "slide scanner mode" that is worthless. The image is so blurred and miscolored that it isn't worth saving. All in all, modern scanners are far worse in quality than old ones - which is why we keep buying drivers. -- kainaw™ 23:52, 5 November 2007 (UTC)

November 4

Safari

I foolishly downloaded a new beta version of this onto my Apply Powerbook G4 and it is causing troubles. Can anyone please advise how I can delete this and return to the original pre-installed stable version. Thanks in anticipation.--88.109.95.158 00:48, 4 November 2007 (UTC)

See this page — Matt Eason 10:47, 4 November 2007 (UTC)

Thanks for this Matt, but still can't find the uninstaller programme despite the hints given. Any more ideas please?--88.109.95.158 14:09, 4 November 2007 (UTC)

Sorry, I can't check myself because I'm not on a Mac. Can you find /Library/Application Support/Apple/.SafariBetaArchive.tar.gz via the Terminal? The thread that post links to also suggests downloading the beta again and finding the uninstaller in the DMG. — Matt Eason 15:37, 4 November 2007 (UTC)

Looked at that but there is no /.SafariBetaArchive.tar.gz nor could I find this on the hard disc anywhere via 'Spotlight'..ah well.....--88.109.95.158 16:29, 4 November 2007 (UTC)

Can't you just download Safari 3? It's not in beta anymore, I'm using it. —Preceding unsigned comment added by 71.195.124.101 (talk) 16:40, 4 November 2007 (UTC)

It is still in Public Beta, according to Apple's website. --24.147.86.187 16:00, 5 November 2007 (UTC)

According to , minimum system requirements are Mac OS X Tiger 10.4.9 or later, and a minimum 256 MB memory. Safari 3 works on Apple PowerPC G4 processor.

Let us know how it goes ...

--Kushal 22:52, 4 November 2007 (UTC)

Thanks for this but looking at Mac Downloads today the only mention of Safari is "Safari3 Beta".  ! Where do I find Safari3 please?--88.109.95.158 07:02, 5 November 2007 (UTC)

Good question! According to Safari (web browser),

a final version was included as the default browser in Mac OS X v10.3

This does not make sense. Why is a public beta still available (unless it is a Perpetual beta)? ---- Kushal 04:23, 7 November 2007 (UTC)

Backup

I am doing a fresh install of Mac OS X v10.5 Leopard on my computer. I am trying to copy my iLife 06 apps on an external USB hard drive (FAT32) so I can install them on Leopard, however I am unsure if this is possible. If so, is it sufficient to back up just the apps, or do I need to backup other things (i.e. preference files).

Thanks, —Curran _{(talk | contibs | random)} 01:02, 4 November 2007 (UTC)

Along with the .app files, you should backup the library files. Check for individual application names in \Library\Application Support\ and \User\Library\Application Support\. If there are obvious preferences files located in \Library\Preferences\ then it is a good idea to save those too, as they might contain your registration data, etc. Oter than those spots, though, there isn't a lot else that needs to be backed up. --24.147.86.187 14:42, 6 November 2007 (UTC)

Java Virtual Machine/API

I was wondering if someone could explain or point me towards an explanation of the following:

Suppose I write a small Java program which includes the API's found in JFC,AWT,Swing, etc. I write it to create a window, and draw a line on it, or something similar. I compile it and run it, and lo there's my window with a line.

Now, if I run the same program from a terminal when there is no X server, the JVM throws me an error message saying that the Java program is trying to use the X window system, but it's not available. Fair enough!

My Java program is just a string of byte-codes and operands, right? which in theory are restricted to the memory and stack inside the JVM, like a brain in a jar in a mad scientist's lab. I'd like to understand how the JVM recognizes that the brain wants to access something outside the jar, ex the graphics API of the host system, or the sound system of the host, or even to send out a stream of text like 'hello world'.

For example, is there a special opcode that means, 'JVM, take this address and do something with it'

Thanks,

--Duomillia 03:15, 4 November 2007 (UTC)

Well all of the JVMs for each platform know how the platform works- the linux JVM knows where to look to check if the x server is running --ffroth 05:39, 4 November 2007 (UTC)

(ec) A Java program is basically a bunch of opcodes that must be run through a virtual machine, and is restricted to the memory and stack inside it, right. However, you must remember that there are many implementations of the virtual machine, basically one per operative system. In other words, the dudes at Sun (and at other places like the FSF) need to create one virtual machine that understand the Java opcodes per operative system. You cannot install the virtual machine for Windows in Linux, nor the one for OSX under Windows. Therefore, we can assume that, while all virtual machines interpret the opcodes in the same way, their implementation varies depending on the operative system. So, the Java program may have an opcode that says "draw a point", and all virtual machines understand that opcode as to "draw a point". However, the Windows implementation of the virtual machine will use a Windows API function to draw that point, while the Linux virtual machine will use an X API function to draw it.

Yes, there are some opcodes that are translated as "JVM, take this value and multiply it for this one, leaving the result in this variable", or "JVM, call this function with this parameter, and deposit the result in this variable". I don't think the opcodes refer to memory addresses directly, but instead to pseudo-variables. After all, you have a JVM that should take care of all that, and the only way it could really implement all their runtime checks (like not accessing an array out of bounds) if it the JVM had the ability of arranging variables the way it wants.

I am sure all these details are covered in the Virtual Machine Specification. However, if you really want to know, you will have to read it all ;-) -- ReyBrujo 05:45, 4 November 2007 (UTC)

Many of the standard libraries (like the graphics library) use the Java Native Interface to communicate with native code that can access the underlying system. --Spoon! 10:25, 4 November 2007 (UTC)

More specifically, here's what really happens. When you make swing calls those eventually translate to AWT calls (and also to Java2D calls, but those work within the context of windows create by AWT). Newly made (technically newly displayed) AWT components try to create something called their AWT-peer; for every (displayed) AWT component there should be an AWT peer object - the peer object is a platform-specific java object which (by means of JNI or a similar java-to-native interface) creates a component using the native windowing system. So there's a different peerset (bunch of native peers) for each windowing system. Usually most platforms only have one peerset available, but there's no reason why it couldn't have more - for example Java on OS-X could have both a Cocoa peerset and an X peerset (I don't know if it does, but that would a reasonable thing for a full Java distribution to supply). Now how does the platform-independent java component code know which peerset objects to create, you might ask. Peers are all created using an instance (a singleton) of the java.awt.Toolkit class. That singleton in turn is created by code in the Toolkit class, which loads the correct peer toolkit subclass by checking a config string and loading the class it gives. The native toolkit is trusted code in a sealed, signed package (so the SecurityManager lets it make native calls and load libraries). -- Finlay McWalter | Talk 16:13, 4 November 2007 (UTC)

Actually, I should correct myself. The toolkit stuff, above, pertains to rather older implementations of JavaSE, where one could only address one display device. Later JavaSE implementations allow you to address multiple displays, and there's no logical reason why those all have to implement the same peerset (I've not looked at the relevant code for years, so they may very well allow that, and that would mean the toolkit object is no longer a singleton). -- Finlay McWalter | Talk 16:40, 4 November 2007 (UTC)

So, if I understand it, when in my hello_world.class I use system.out.println, it calls the class system which in its own code has a JNI that takes my string of characters and prints it to the standard output. Which means that if someone wants to port a JVM to a new system, they have to rewrite the JNI code in all of the java class standard libraries to suit the new platform.

Follow up question, how does the JVM know to transfer control from the java bytecode to native code? Is there a special opcode for that? --Duomillia 01:09, 5 November 2007 (UTC)

There should be, yes. In assembler, you have code like:

PUSH ebx

CALL _function

So, in Java there should be an opcode that tells the VM to invoke a determined function. Whether that determined function calls another Java function or a native one, it should be transparent for the caller. -- ReyBrujo 01:43, 5 November 2007 (UTC)

While Java bytecode has many of the features you'd expect to find in an ordinary assembly language, it does differ from them in some ways. One is that all Java bytecode programs are divided into methods, each of which is mostly self-contained; in particular, each method lives in its own address space. The only way for one method to call another is by a specific opcode for this purpose. This is a fairly high-level operation: the calling method simply supplies the name of the class and the method it wants to call, and the JVM internally does all the work of locating and (if necessary) loading the class in question, checking that the calling code is allowed to call that method, obtaining a lock if the method is synchronized and so on. As it happens, some methods may be marked as "native": these look like perfectly ordinary methods to the caller, but they're not actually written in bytecode at all. Instead, when they're called, the JVM simply passes control to a native subroutine that does whatever the method is supposed to do. The way in which such methods are implemented may be JVM-specific, but the Java Native Interface mentioned above is one possibility. —Ilmari Karonen (talk) 05:00, 5 November 2007 (UTC)

New nVidia GPU power consumptions.

I'm considering getting one of the following nVidia GPU units,

1. 8800GT
2. 8800GTS (320mb)
3. 8800GTS (640mb)
4. 8800GTX

and I'd would like to know, how much power, in watts, do each of them take up idle, and under a full load?

Dryir Lent 05:56, 4 November 2007 (UTC)

"G80 core can peak at 145.5 Watts with 116.6 on average during gameplay," apparently. Our article says 145 for the GTX. FiggyBee 08:51, 4 November 2007 (UTC)

That's just the core though - the ram and the cooling fan will add to that. SteveBaker 16:33, 4 November 2007 (UTC)

Actually I was hoping to get answers on the new G92 cores, although I should have been more specific I suppose. 75.164.208.153 22:10, 4 November 2007 (UTC)

The G92s use slightly less power. See - "the 8800GT (G92) consumes the least power, very much due to its smaller die". FiggyBee 22:19, 4 November 2007 (UTC)

Posting a picture online

How do you post pictures online? Also, how do you store pictures on your computer? Can you store old pictures on your computer or do they have to be on a disc? And what special equipment, if any, is needed to scan, store and post pictures? —Preceding unsigned comment added by 63.237.114.10 (talk) 07:44, 4 November 2007 (UTC)

• We can post pictures online by uploading them to a web server (basically a high end computer that is always connected to the Internet). Flickr, Picasa are two good services which have free as well as paid-for services. --Kushal 20:16, 4 November 2007 (UTC)

• Most of the time, we store pictures on a computer by saving it on the hard disk drive. --Kushal 20:16, 4 November 2007 (UTC)

• It depends what you mean by a disk. Some people call flash drives by the name of flash disk. If you mean a circular optical disk, then no. The pictures do not need to be on a CD or a DVD. --Kushal 20:16, 4 November 2007 (UTC)

• Please see Image scanner for more details on this question. --Kushal 20:16, 4 November 2007 (UTC)

Hope that helps! --Kushal 20:16, 4 November 2007 (UTC)

mp3 players with radios

Why don't mp3 players have AM radio stations? They only have FM stations. —Preceding unsigned comment added by 121.218.52.137 (talk) 11:40, 4 November 2007 (UTC)

Because AM radio need a large antenna due to their larger wavelength, and they can't fit one in one of today's minuscule MP3 players. --antilived 19:09, 4 November 2007 (UTC)

Yep, AM radio needs either a (relatively) bulky Loop antenna, or a *very* long wire. FM radio only needs a shortish wire - portable players use the headphone cable as the FM antenna. FiggyBee 21:38, 4 November 2007 (UTC)

So that is the reason why FM won't play without headphones? --Kushal 22:42, 4 November 2007 (UTC)

What kind of player is this? The headphones might have the antenna in them. —Preceding unsigned comment added by 71.195.124.101 (talk) 23:35, 4 November 2007 (UTC)

They frequently do, most peoples phone radios will not operate without the headphones inserted for this very reason. Lanfear's Bane | t 10:29, 5 November 2007 (UTC)

patitioning a hard drive

can making a disk partition corrupt data on you hard drive? if so, how do you avoid it?

P.S.-Can you install Ubuntu on an existing partition?--67.84.12.248 20:38, 4 November 2007 (UTC)

It can be tricky to figure out the process of repartitioning (and you may lose data trying to figure it out) but losing data isn't a necessary part of the process. I've performed half a dozen repartitionings on my current computer with no problems at all. There used to be problems with resizing NTFS partitions but now gparted and its ilk can easily do it, without prior defragmentation, with zero risk. Also no you can't install ubuntu on an existing partition unless it's linux-compatible (fat, ext, reiserfs, xfs), and even then I think you lose all your data on that partition. --ffroth 20:45, 4 November 2007 (UTC)

(Froth will kindly correct me if I am wrong) If your current partition is empty, you can install Ubuntu on it. Ubuntu will format your partition to ext3. --Kushal 22:34, 4 November 2007 (UTC)

glgears

Is their a port of glgears for mac? I'd like to use it to compare ppc emulation against native intel code. —Preceding unsigned comment added by 71.195.124.101 (talk) 23:41, 4 November 2007 (UTC)

There's a '/usr/X11R6/bin/glxgears' on my Mac, however, it uses X11.app. -- JSBillings 03:15, 5 November 2007 (UTC)

Using that particular program will test only the performance of the OpenGL interface to your graphics card under the emulation versus the real thing. The actual CPU time required is near zero if the graphics card is being used for rendering - and if graphics hardware is not used in the emulation, you won't be measuring the relative performance to the emulator versus the native code so much as software OpenGL rendering versus hardware rendering. At any rate, I thought glgears used GLUT - that being the case, if you download 'freeglut' ( http://freeglut.sf.net ), you should be able to compile it for native MacOSX without X11. SteveBaker 05:05, 5 November 2007 (UTC)

GlGears is entirely useless as a benchmark - it doesn't test any of the stuff you care about for any modern application (bendy windows, direct-video-access, transparency, shaders, textures, lighting, geometry handing, etc.). Worse, many drivers clamp the framerate: so on Linux I get far higher GLGears framerates using the software Mesa driver (which of course doesn't really do real stuff very quickly) than with the NVIDIA driver (which does games, compix, etc. very nicely). There's more rant on similar lines here. Of course this begs the question - if GLGears isn't a decent modern cross-platform GL benchmark, what is? The Lunchbox of Dooom 13:01, 5 November 2007 (UTC)

To answer my own question, Piglit (and the Glean tests it includes) seems to at least be an attempt at a GL benchmark; I don't know how well its results will correlate with the actual game/fancy-window performance. And what Steve said above will still be true - most of the work is being done in the GL subsystem. -- The Lunchbox of Dooom 13:08, 5 November 2007 (UTC)

Yep - I agree. The load that glgears imposes on even a software renderer is nowhere near high enough. The fact that no part of the image is textured or fogged is a huge matter. Software rendering can actually be quite fast on flat-shaded stuff - it doesn't start to really show it's lack of performance until you have really complex per-pixel operations going on. These days, any graphics card test that doesn't pummel the shaders hard is a bad test - which means that anything that'll run on OpenGL 1.xx is a useless test of graphics performance. I would take a look at the latest graphics and CPU reviews out there and see what the reviewers are using. IMHO, the only valid test is to run the kinds of applications you actually want to run...and I strongly suspect that won't be glgears! SteveBaker 19:09, 5 November 2007 (UTC)

November 5

Buying a Computer Server..

I want to buy a server for holding a website.. live server (24/7).. in the range of $3,000 (a bit more or less, ok).. what's the best server for me?? thanx in advance.. Ahmad510 00:12, 5 November 2007 (UTC)

Apple offers one starting at USD 2,999.00 with free shipping. I do not recommend buying right away but try to see the configuration of the computer. Maybe you could be adventurous and build your own computer by buying the parts. --Kushal 01:41, 5 November 2007 (UTC)

Thank you Kushal.. but i need it to be compatible with Windows Server 2003.

Almost any new industry standard PC could run a server. Your specs will depend on what kind of load you expect - are there thousands of hits per second expected? Is there going to be input to the website? Are there terrabytes of data? Will much money be lost if the server is down? Graeme Bartlett 02:44, 5 November 2007 (UTC)

The server will be used for holding an online bookstore, i don't expect those "thousands of hits per second", no huge inputs or terrabytes of data.. and if the server is down, actually i'll feel so bad..

A bigger concern than the server itself would be other infrastructure it depends on. Do you have a backup power generator and redundant internet connections, for example? If you want reasonable reliability, you probably want to look at paying someone to host the site for you. Then, the server is their problem, not yours. Friday (talk) 20:15, 5 November 2007 (UTC)

You probably don't want to try to host a commercial web site over your home internet connection. Your options are to lease a server (or shared server) or co-locate your server. The former will be the most economical approach, although you will usually not have full control over your server. For co-location, you'll want to look at getting a rack-mount server (the Xserve is just one example of that, and while it can run Windows Server 2003, you'd be paying a premium for another operating system you're not using). A bit of searching will turn up some build-to-order options. Note that shared server hosting costs can range from as little as $10/month to as much as $150-200/month. The cheapest co-location I've found is $75/month for a 1U server. Donald Hosek 00:00, 6 November 2007 (UTC)

Are you sure they have PPC builds of Windows 2003? --ffroth 04:46, 6 November 2007 (UTC)

That's an Intel Xserve. Pinball22 04:52, 6 November 2007 (UTC)

The idea of leasing a server isn't applicable at all for the owner of the website (I'm not that owner for sure).. and regarding the infrastructure, the server will be run using a high-speed DSL internet connection without a backup power generator or a redundant internet connections.. anyway such appendants will be handled later on if necessary.. Thanks for the contributers.

Recording Onto CD.

I was just wondering is there anyway I can record sound onto a CD using a 1/4" microphone jack? The same kind used with a kareoke or singers in concerts. Apparently it is possible but I have to get a CD recorder or use a computer for it.Jwking 02:14, 5 November 2007 (UTC)

You will need a microphone, which could have a plug to fit this size hole, then plug into your computers microphone socket on the sound card or mother board. Run a piece of software that can record. You then need a CD burner to make the CD. You can also by special CD recorders from a Hi Fi shop, but expect to pay considerably more than a PC for this. Graeme Bartlett 02:38, 5 November 2007 (UTC)

Or put another way: you don't burn directly to the CD from the microphone jack; it isn't like a cassette tape. What you do is record to your computer from the microphone (save it as a WAV or MP3 file, for example), and then burn the sound file to the CD with a CD burner (which can save it as an audio track so it will play in a CD player). You should use a computer for this, as it will already have most of the necessary components (mic jack, operating system, recording softwase) built into it. --24.147.86.187 15:39, 5 November 2007 (UTC)

"Total" row in PostgreSQL

I'd like to create a view that contains first the result of

SELECT "All Cards"."Rarity", sum("All Cards"."Non-foil"), sum("All Cards"."Foil"), sum("All Cards"."Total") FROM ("All Cards" JOIN "rarities" ON "All Cards"."Rarity" = "rarities"."value")
GROUP BY "All Cards"."Rarity", "rarities".sort_order
ORDER BY "rarities".sort_order

and then the result of

VALUES('Total', (SELECT sum("Non-foil") FROM "All Cards"), (SELECT sum("Foil") FROM "All Cards"), (SELECT sum("Total") FROM "All Cards"))

But I cannot simply join them with a UNION as long as the ORDER BY clause is present, because ORDER BY a non-result row is illegal (and generates an error message as such) when UNION is used. And if I drop the ORDER BY clause, Total isn't the last row and Uncommon isn't between Common and Rare. How can I define a view as the combination of these two queries, with the other rows in order and the Total row last, and without adding a superfluous column to contain sort_order? NeonMerlin 03:24, 5 November 2007 (UTC)

What's the on-screen arrow called?

It seems like "cursor" is used a lot, but does that really apply to GUIs? I think of the old blinking square. "Pointer" doesn't seem to be accurate either as it implies passivity (like a laser pointer -- it doesn't perform any actions). --24.249.108.133 06:41, 5 November 2007 (UTC)

I say "cursor" or "mouse pointer" or "mouse cursor". And I never even thought of it as an arrow until you pointed it out --ffroth 07:35, 5 November 2007 (UTC)

I would refer to it as the cursor or not use a noun and ask someone to "move the mouse to" or "mouse over". Also technically should we refer to it as an arrow head? It has very little shaft and no fletchings. It's more of a dart technically and don't forget you can change it from it's default to just about anything. Lanfear's Bane | t 10:27, 5 November 2007 (UTC)

It is officially a cursor, as Microsoft and Borland GUI development tools use that term in their components. It cannot be called an arrow as it could be changed to anything depending on your theme - even a dancing horse! Pointer is also acceptable as it always has a "hot spot" for you to click on items. Sandman30s 11:53, 5 November 2007 (UTC)

It is the cursor or the mouse pointer, and it has different states, one of which (the default) displays an arrow head. Others are the I-bar (for editing text), the compass-rose (for moving things around), the wait cursor (the hourglass), etc. Programmatically it is referred to most often as the Cursor and sometimes as the Mouse Pointer. --24.147.86.187 15:36, 5 November 2007 (UTC)

Even in DOS (or cmd) when it's just a flashing box or symbol it's still called a cursor. You can refer to the mouse cursor as the mouse cursor, there's a text cursor, etc. Rfwoolf 15:41, 5 November 2007 (UTC)

I prefer "pointer" to avoid ambiguity with the text cursor. I'd also be cautious about prepending "mouse" given the availability of other pointing devices. NeonMerlin 18:23, 5 November 2007 (UTC)

Eh, just because it's not used with a mouse doesn't mean it isn't clear. I use a trackpad (on a laptop) and if someone called it a "mouse pointer" I would know what they meant and would certainly not take any offense. --24.147.86.187 01:55, 6 November 2007 (UTC)

In formal writing, I'd use 'pointer' - but informally, 'cursor' works too. 'Arrow' doesn't work because sometimes it's an egg-timer or a cross-hair or something. SteveBaker 19:04, 5 November 2007 (UTC)

"Arrow" is also used for a number of keys on the keyboard ("arrow keys") and so you'd want to avoid any ambiguity there ("Click the button with the arrow" is ambiguous to me). --24.147.86.187 17:53, 6 November 2007 (UTC)

Making Windows 98 printer drivers work on XP

I've got a Lexmark 2050 colour printer running on an old Windows 98 machine. There is no driver for this printer for XP. The 98 driver doesn't work on XP and using the XP driver for closest model, the 2030, just gives garbled data. It's been an interesting problem and I've thought of a few things which might tax the brains of teh people here:

1. Is there any way to get the printer and OS talking? I assume Virtual PC or VMWare would work but that is rather extreme. Nor do I want to dual-boot every time I want to print.
2. Is there a Windows 98 emulator for XP out there anywhere? (Kinda like DOSBox.)
3. Is there some sort of "wrapper driver" that can get the 98 driver talking to XP?
4. How difficult are wrapper drivers to code? Or are they just impossible?
5. What is so fundamentally different between the two OS's driver handling that XP cannot interpret the commands designed for a 98 driver?

Thanks for the help. Zunaid©® 10:46, 5 November 2007 (UTC)

There is Microsoft Virtual PC 2007, apparently free for download, which I believe you can use to emulate and install Windows 98 (if you have a copy of the CD, of course) on a virtual "partition" of your hard drive". There are emulators out there which allow you to "save the state" of a virtual machine so it doesn't require "booting" per print, although it might need a restart every now and then. I do think it's more extreme to start thinking about rewriting drivers to cooperate, because it's not easy and because these drivers operate at assembly code level or deeper (which explains why XP drivers may not work on 98, for example). x42bn6 Talk Mess 13:26, 5 November 2007 (UTC)

Recover photos from wonky flashcard

There's a popular piece of open-source software that helps rescue files from damaged flash cards; I just can't remember its name. I've seen it recommended on this page several times - can anyone remember its name? The Lunchbox of Dooom 13:18, 5 November 2007 (UTC)

PhotoRec and/or TestDisk. --LarryMac | Talk 14:44, 5 November 2007 (UTC)

Help with internet connection

My internet connection seems to "die" on my somtimes. I cant connect to any games on LIVE or be on aim and[REDACTED] at the same time. I have wireless internet thats unsecured could that be the problom? Also i have comcast Jack THE Pumpkin KING 17:36, 5 November 2007 (UTC)

Using unsecured wireless is a really bad idea - unless your home is at really good distance from where anyone else lives or works or parks their car. My 'weekend' home is like that - it's out in the woods, half a mile from the nearest other building and a quarter mile from the nearest road - so I don't bother to secure my WiFi. But my apartment here in Austin has maybe 100 active computer users within range of the transmitter, so it has the maximum level of protection enabled! I also had to be careful to tell my computer to use that WiFi connection point ONLY and not to pick up one of the half-dozen unsecured access points in the area! It's perfectly possible that enough other people are squatting on your signal to prevent you getting access - but it's also possible that your PC is latching on to someone elses unsecured access point. The way most people set up their computers, they may actually be trying to legitimately get to their own WiFi box - but because yours was auto-detected, they may be picking up a poor/overloaded signal from your WiFi box and using that instead of their own perfectly good one. You should secure it - immediately - and also make sure your PC and game machines are set up to ONLY access your box. SteveBaker 19:02, 5 November 2007 (UTC)

The problom is how do i secure it. i had my father try to but he said sometinh about a w12 code or someting like that. Jack THE Pumpkin KING 19:04, 5 November 2007 (UTC)

You're still using it and you haven't secured it? OK do this ASAP. Comcast gives some good advice- first turn off SSID broadcasting and change your network SSID. This makes it difficult for attackers to "tune in" to your network's wireless signal without knowing the name of the network. You'll have to manually set up each of your wireless computers to use that network ("Manually connect to a wireless network" or something like that for vista) because they won't autodetect it. Next enable WPA encryption- don't listen to Comcast on this point, they probably just want you to use WEP because they don't want to have to upgrade the ancient routers they lease out to customers. WEP has serious flaws to the point where it's barely better than no security at all. Finally if you want ultimate security, use static IP addresses (disable DHCP on your router) and only allow access to the MAC addresses of the computers that you want have the ability to connect the network with.. to.. --ffroth 22:14, 5 November 2007 (UTC)

Why do magnets render disks unredaable, and do they do the same w/DVDs?

A good friend told me his brother worked for a computer store, and one day a woman called and said her disks she bought were defective; here she'd stuck them to her refrigerator with magnets. (And you thought you heard 'em all about dumb things people do :-) My question is, first, why did magnets do that to disks, and second, are DVDs safe from those who would stick them someplace with magnets? I could see a magnet erasing a disk, but why would it render the disk inoperable?Somebody or his brother 19:32, 5 November 2007 (UTC)

Magnetic media can be disrupted by magnets. Optical media wouldn't be, unless the magnet happens to scratch it or something. Friday (talk) 19:34, 5 November 2007 (UTC)

Thanks - I hadn't really understood magnetic fields and such, but I'm understanding it now, after having read that and a couple other linked articles.Somebody or his brother 20:10, 5 November 2007 (UTC)

A magnet will not only erase the user's data from a magnetic disk but also the low-level formatting data. The disk can still be reused if it's reformatted, but this user might not have known how to format disks (most disks these days being sold preformatted). -- BenRG 22:21, 5 November 2007 (UTC)

Basically disks, as magnetic media, have their information inputted by a varying magnetic field which inputs the 1's and 0's as different magnetic fields. VHS and cassette tapes work the same way. CDs and DVDs instead have their data on them (still 1's and 0's) put in place by burning a little hold in the plastic of the disk with a laser. --01:57, 6 November 2007 (UTC) —Preceding unsigned comment added by 24.147.86.187 (talk)

CDs and DVDs don't have holes burned in them by lasers. CD-R and friends use a dye that changes its reflectivity when heated. Mass-produced discs are injection-molded (see compact disc manufacturing). Even mass-produced discs don't have actual grooves in them, just variations in the depths of internal layers. -- BenRG 19:27, 6 November 2007 (UTC)

Cellular/wireless "bars"

Is there an article specifically about the iconography that is commonly used in mobile phones to indicate the signal strength? What are they called? They look like a stylized representation of an antenna(?), and to the right of them there are up to five vertical bars of increasing height. They're currently used in Cingular's advertising, and the Sprint Nextel article says that Nextel used it in the past in their advertising and that the current logo is derived from it. —Random832 19:48, 5 November 2007 (UTC)

The Y-shaped icon is a universal electronic symbol for antenna. The bars, however, don't actually mean anything. They are subjective, similar to an S meter. --Mdwyer 20:26, 5 November 2007 (UTC)

Mdwyer is correct. If you move your phone and the number of bars increases, the strength of the signal between the phone and the Cell site it is connected to also increases. However, the number of bars displayed for a given absolute signal strength differs between Cellular networks. The voice quality of any particular call does not necessarily correlate with the number of bars, but in general, the more bars displayed, the more reliable the connection and the clearer the voice quality will be.Thomprod 22:24, 5 November 2007 (UTC)

its not correct to say they mean nothing. They are the signal strength in db relative to the background noise. The reason that people say they 'mean nothing' is that signal strength has little to do with quality of reception for digital spectrum sharing. You drop out and get no signal when there is simply no frequencies available to transmit on or people are transmitting over you. —Preceding unsigned comment added by Dacium (talk • contribs) 06:37, 6 November 2007 (UTC)

November 6

Odd website

Hi all,

I recently came across this cached website: http://72.14.253.104/search?q=cache:MLQKinzVpMIJ:special.sword-desk.nl/1/50.html+%22%22&hl=en&ct=clnk&cd=16.

What on earth is the purpose of it? It looks like it has just taken random sentences/words from the internet and stuck them together, my favourite line in it has to be "You address labels. address labels adaptation of squids". Why would someone create a bot to create a page like this!?

Aaadddaaammm 04:54, 6 November 2007 (UTC)

Perhaps some form of spamdexing? --Spoon! 05:05, 6 November 2007 (UTC)

Hmm, yea it does seem to have parallels with Scraper site, but there's no advertising on the site! All the links (as far as I can tell) point to further pages whose urls are very similar to this one (although all these links seem to be dead)... any other insights? Aaadddaaammm 05:12, 6 November 2007 (UTC)

A fun experiment? That would make epic bragging rights to show your friends that you wrote some script and now your page is on the top 10 google results --ffroth 05:19, 6 November 2007 (UTC)

Firefox "restore session"

I tried to start Firefox (2.0.0.9) from a previous session, but it keeps crashing after seemingly loading all my old windows. Is there some file on my system to which Firefox saves the URLs and window configurations so I can open the pages manually and try to sniff out the bad apple? --151.200.19.209 05:05, 6 November 2007 (UTC)

Dont use session restore. If you let firefox crash to much it might delete/corrupt all saved bookmarks/history/passwords/form info. —Preceding unsigned comment added by 24.250.139.137 (talk) 09:18, 6 November 2007 (UTC)

Yes, Firefox seems prone to corrupting bookmarks etc, I've had it happen about three times although the latest version seems more stable. When you start it, it should ask if you want to restore your previous session and start a new one, if you start a new one, you should be OK. The other thing that I find Firefox doesn't like is opening PDF files. Best to download them and read them in the standalone Acrobat Reader. GaryReggae 13:03, 6 November 2007 (UTC)

But what of my old windows? There were pages I wanted to read, and I'd rather not start hunting through my history for them... --151.200.27.252 13:39, 6 November 2007 (UTC)

In my experience, if 'Restore previous session' crashes Firefox, I start a new session and my last viewed pages have been added to History - Recently Closed Tabs. 86.21.74.40 14:40, 6 November 2007 (UTC)

If you know which tab crashes Firefox, you can try to close it as soon as it begins loading. If you don't know, you are out of luck. -- ReyBrujo 04:19, 7 November 2007 (UTC)

Have you tried loading Firefox in safe mode? It might be a misbehaving add-on for all I know ... ----Kushal 04:28, 7 November 2007 (UTC)

Haywire - a new virus?

When I log onto certain news orgs or or other "legitimate" sites (like the New York Times) and a pop up ad or message tries to popup but gets blocked a system message will come up that says a device, etc. can not be accessed. Then when I click "OK" all hell breaks loose and blank web pages start popping up until memory is filled and the computer locks up. How can I stop this? Dichotomous 05:22, 6 November 2007 (UTC)

... it would help if you told us what browser and what operating system for a start --Dacium 06:32, 6 November 2007 (UTC)

If you had any knowledge to impart you would already know which browser and OS. Dichotomous 20:53, 6 November 2007 (UTC)

How can we know which browser version and which OS and its version? You are an ungrateful moron.--Dacium 05:17, 7 November 2007 (UTC)

If you were familar with the problem then you would already have this information. Pretending like you can solve a problem you are not familar with by asking for the browser version and OS makes you the moron. Dichotomous 13:57, 7 November 2007 (UTC) —Preceding unsigned comment added by Kadiddlehopper (talk • contribs)

And if you are worried about a virus or malware you should first try scanning for it. Try AVG or SpyBot if you don't have virus and malware scanners. --24.147.86.187 14:28, 6 November 2007 (UTC)

Had I not already scanned for a virus, malware or spybot there would be no point in posting this question here. Dichotomous 20:53, 6 November 2007 (UTC)

I'll take a guess at your OS - Windows XP, Service Pack 2, and browser - Internet Explorer 7. If these are incorrect, could you please correct me - unfortunately, my ESP is on the blink. Do you have an example of a page which is trying to open a pop-up? On the New York Times website, for example? I haven't been able to find any pop-ups there yet. Are the pop-ups legitimate NYT content, or spam advertising? What is the exact system message you are receiving? Have you tried running a Hijack This! log to check what is running on your system? Diagnosing a problem remotely is difficult - precise information would be useful. Thanks! --Kateshortforbob 12:13, 7 November 2007 (UTC)

It's actually Winx64 SP2 IE6, but you would most likely already be familiar with this if you were aware of the problem. It appears that whenever a site is accessed IE uses 2 browser windows instead of one. I think this is done on Winx86 SP2 IE6 as well in order to keep the link open or some other similar reason. In the case of Winx64 SP1 or SP2 IE6 or IE7 the second IE browser window is not hidden or minimized. When a web site component can not find hardware it wants like a sound card maybe or uses popups and is blocked or can't find the hardware it tries again by opening another pair of browser windows and has somehow not been prevented from doing this over and over again up to about 300 new windows. Its kind of like an absence of the routine that prevents more than one instance of a link coming up beyond the first one no matter how many times you click the link after the first. The problem is caused by the web site but not prevented by the IE or OS. Dichotomous 14:09, 7 November 2007 (UTC)

HDTV mpeg2 bit rate

What is the average bitrate for HDTV (1920x1080 5.1 audio) MPEG2 compressed terrestrial TV as transmitted for example in Australia? I have some HDTV receiver cards that I want to put into older PCs to save video to harddisk. I know that PCI is limited to about 533MB/second and my IDE harddisk is limited to just 133MB/second. Each card can decode 2 channels at once, but I wonder how many MB/second a single HDTV mpeg channel would be on average?--Dacium 06:09, 6 November 2007 (UTC)

Might have found the answer: MPG2 High Level is 1920x1152x30fps, and has a bit rate of 80Mb/s (10MB/second). So it should be possible to stream multiple channels at once, I was only hoping to do 6 channel to 3 different harddrives.--Dacium 06:14, 6 November 2007 (UTC)

That figure sounds a bit high; standard definition channels in the UK are only about 3Mbit/s. -- DatRoot 15:14, 6 November 2007 (UTC)

You will find the bottleneck of disk writing comes a LOT sooner than 133MB/sec, unless you are using a very very fast RAID setup. Practical streaming is 20-30MB/sec under perfect circumstances, even with the latest IDE disks. However, the bitrate of 80Mbit for broadcast HDTV is quite high. Using Australia's DVB-T (as an example) allows for at most 30 mbit per channel, but more likely 15 mbit or lower depending on station circumstances, which translates to a more manageable 2MB/sec stream. --Jmeden2000 16:16, 6 November 2007 (UTC)

Setting up a LAN

What would be a good hardware/software system for setting up a LAN that connects to the internet for a school of about 1,000 student with around 200-300 computer access points? As well, would the type of computer-Mac or PC-matter? Thanks. 71.18.216.110 14:36, 6 November 2007 (UTC)

The type of computer doesn't matter in any way. All it needs is a network adapter. You will need a gateway with DHCP running. That will be your connection to the Internet. Every computer will contact it to get to the Internet. Then, you can run the normal spiderweb of network cables to switches and set up wireless access points. There is nothing special or abnormal about it at all. There's no "good" hardware/software system either because there are so many alternatives. Technically, you could get a $50 Linksys router and run it through a bunch of switches - but it can only handle 253 computers (at a rather slow speed due to bottlenecking). -- kainaw™ 14:41, 6 November 2007 (UTC)

Search & replace => keep some of the text found_keep_some_of_the_text_found-November_6-2007-11-06T15:35:00.000Z">

Hi all,

I've got a large number of web pages that include some text wrapped in now defunct div's: <div class="decrecated class">some text</div> .

I want to remove all those divs. I could easily use search&replace to remove the first half, but then I'd be left with a lot of hanging </div>'s, which I couldn't remove using s&r (because it would remove the ones I want to keep).

I know a little bit about using regular expressions in s&r, but is there any way to delete just a part of what you find, or to replace it with a piece of what you found? I'd like to say: "Search for '<div class="decrecated class"></div>', replace it with ''". Is anything like that possible?

Thanks!

Sam, 15:29, 6 November 2007 (UTC)

Yes. Regular expressions are the way to go. You'll want to replace something like "<div*>(*)</div>" with "$1". The syntax of your editor may be different. The idea is to catch the part inside the div with parenthesis and then paste it back out using the $1. -- kainaw™ 15:35, 6 November 2007 (UTC)_keep_some_of_the_text_found"> _keep_some_of_the_text_found">

Restore copied over files

Daaamn! I have just been an idiot and copied html files from a ftp server over the files it had just taken me all day to update on my hard drive. Yes I inverted my 2 windows explorer windows, yes I should have used a proper ftp client, yes I'm an idiot. Please help is there any way to get the files back? Keria 15:42, 6 November 2007 (UTC)

Nope! Sorry 'bout that. Writing over a file is one of the almost sure-fire ways to render its data unaccessible (much worse than just deleting it, as it turns out, since the latter just flags is as free data that can be overwritten in the future). But if it makes you feel better it is happened to all of us at one point or another. --24.147.86.187 15:54, 6 November 2007 (UTC)

"Writing over" can mean two different things:

1. Opening the file for read/write access and writing new data over what's already there.
2. Opening the file for (over)writing.

The FTP program probably did the second; it would be very strange to do the first. This is similar to deleting the file and then creating a new one with the same name. There's a good chance that the old file's contents are still on the disk somewhere, since there's no particular reason for the filesystem driver to use the old file's clusters for the new file. However, the directory entry has most likely been overwritten, which means the simplest approach to undeletion won't work. You would probably have to search through the free space of the drive for relevant phrases from the files to find them. There are various free Windows programs that can help with this (e.g. HxD). -- BenRG 19:41, 6 November 2007 (UTC)

Ah typing through the flood of tears streaming on my keyboard (not really). I loaded all those pages to test them in Opera. Is there a memory of them somewhere? Keria 16:10, 6 November 2007 (UTC)

• I have successfully retrieved lost data under Linux by simply copying /dev/mem to a file and searching for known text. Perhaps Windows has some equivalent feature? --Sean 16:31, 6 November 2007 (UTC)

Oh, if you loaded them in a browser, maybe, MAYBE! Make a quick copy of the cache directory (before it get overwritten or cleared) and search around inside it for text you know would be in that file. --24.147.86.187 17:50, 6 November 2007 (UTC)

Windows 2000

Hello, i have reinstalled windows 2000, downgrading from xp, as my laptop is from 2000, I formatted, and the thing is now clean, and runs beautifully. Thanks for all the help. I now have no sound. i have tied the start,settings, contol panel, sound options, hardware says the sound is installed and running fine, however, audio, the previous tag is all unuseable, unhighlighted. i have a dell latitude cpx. Thankyou again. —Preceding unsigned comment added by 82.3.149.242 (talk) 18:44, 6 November 2007 (UTC)

Go to http://support.dell.com and ensure you've installed the proper sound driver. -- kainaw™ 18:49, 6 November 2007 (UTC)

Mouse droppings?

I use a hard plastic mouse pad and an optical mouse. Every few weeks I notice that there are these little hard black spots on my mouse pad that need to be scraped or cleaned off. Is it the non-stick mouse surface rubbing off? What is it caused by and is there any way to prevent them? --24.249.108.133 21:49, 6 November 2007 (UTC)

They're the same thing that clogs up non-optical mice: skin oils, dirt, and other miscellaneous crud. The advantage with the optical mouse is that they'll just create less-slippery spots on the mousepad, they won't gum up the interior workings of the mouse.

Atlant 23:37, 6 November 2007 (UTC)

How would I network a computer using Windows 3.1.1

I need to get a working internet browser with online access for 3.1.1. What would be the easiest way to do that? The computer is an old pentium 3 compaq. I can post more specs if need be. —Preceding unsigned comment added by 24.117.137.182 (talk) 22:21, 6 November 2007 (UTC)

You'll need a working Winsock stack, and maybe an old old copy of Mosaic. I can't remember what other browsers might have been available way back then, and I was more of an OS/2 guy anyway. Are you going to use dial-up? --LarryMac | Talk 00:13, 7 November 2007 (UTC)

Ah no, 3.11 (which was "For workgroups") has an MS produced TCP/IP stack; the first version of Windows to do so. IE was available in the "Plus Pack", but there are still versions of IE, 5.01 floating about. --Blowdart | 08:19, 7 November 2007 (UTC)

No im using cable, i found a browser for it but i dont really know what winsock is? what does it do? —Preceding unsigned comment added by 24.117.137.182 (talk) 00:26, 7 November 2007 (UTC)

You can try to get hold of the trumpet winsock, a TCP stack for windows. This is a shareware that may or may not still be for sale. The winsock profides an interface for programs to do TCP IP, it has a library of procedure calls to make data travel on a network. It also has to interface to the low level holes in the computer to get the data in and out, such as the modem or ethernet driver. Graeme Bartlett 00:55, 7 November 2007 (UTC)

Winsock provides the TCP/IP networking functionality; I think we can safely assume that's the kind of networking you're looking for. But if not, you might want to also see Windows for Workgroups.

Atlant 00:55, 7 November 2007 (UTC)

Offtopic but why you need Windows 3.1? Pentium 3 isn't that old and Windows 98 will run comfortably on a Pentium 500Mhz, or even a Linux distribution like Xubuntu with wine will be able to run a lot of the windows programmes, and dosbox for dos programmes. --antilived 04:43, 7 November 2007 (UTC)

Used computers that will run Windows XP are getting very cheap (~ $300 on Craigslist). A newer machine might preserve your peace of mind. My memory is that networking on Windows 3.1 was a pain. Be prepared to do some user-unfriendly installation and deinstallation. You may need to find some old books to walk you through the setup. If you need to replace any hardware pieces they may no longer be available, or may not come with drivers for Win 3.1. EdJohnston 05:23, 7 November 2007 (UTC)

Forcing firefox to open

I don't know if this bug anyone else, but when I click on a hyper link in Thunderbird or Messenger it automatically opens in IE, which is downright annoying. Is there anyway to get FF to open automatically? Cheers Jackacon 22:59, 6 November 2007 (UTC)

Which version of Windows? On XP (SP2) there should be an item on your start menu called "Set program access and defaults" which will let you specify default web browser, email, media player and instant messenger programs. In addition, you might want to go to the Firefox Tools/Options/Main window and use the button at the bottom to check if Firefox is your default browser. --LarryMac | Talk 00:06, 7 November 2007 (UTC)

November 7

HTML keys?

Are there command keys that let you see the html of a web page? I use a mac tigerJulia Rossi 00:21, 7 November 2007 (UTC)

Assuming you're using Safari (and assuming the Mac version's menus are the same as the Windows version's), go to View and click View Source. Apparently the keyboard shortcut is Command-Option-V; can't check though, I'm not on a Mac. — Matt Eason 00:36, 7 November 2007 (UTC)

Command+Option+U, but yeah. --24.147.86.187 04:08, 7 November 2007 (UTC)

4 x NVIDIA GeForce 7300 GT 256MB vs NVIDIA Quadro FX 4500 512MB, Stereo 3D (2 x dual-link DVI)

Looking at Apple online store's Mac Pro customization options ], under the graphic card options, there is an option of four NVIDIA GeForce 7300 GT 256MB or a more expensive, single NVIDIA Quadro FX 4500 512MB, Stereo 3D. Looking at the price, is the Quadro FX truly better than four GF 7300's? Thanks. Acceptable 01:09, 7 November 2007 (UTC)

For video rendering? Ohhhhhhh yes. -Wooty   10:36, 7 November 2007 (UTC)

Second Life and Vista

I used to have alot of fun on my Second Life account until I bought this new computer. Now when I try to freelook (click on my character and look around) in Second Life, the camera flips around over and over at dizzying speeds. Apart from upgrading the hardware, the only changes I've made have been upgrading to Vista and changing my monitor over from 4:3 to 16:9. Could either of these 2 changes account for this disturbing error in gameplay? Sappysap 01:54, 7 November 2007 (UTC)

Try turning off mouse acceleration in your mouse settings? That sometimes wreaks havoc with mouse sensitivity in games --ffroth 04:11, 7 November 2007 (UTC)

System requirements for installation of Visual Studio.NET on Windows XP Service Pack 2

Which framework do i need to install and what are the system requirements?

win98SE USB webcam

I am running Win98SE and have a USB card and a webcam. Is there software I can use to view the images produced by the web cam? The USB card has a USB 2.0 driver but the web cam came without a disk and is labeled "driverless?" Clem 13:37, 7 November 2007 (UTC)