Wikipedia:Reference desk/Archives/Computing/2009 January 28

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January 28[edit]

found it, but what's it called?[edit]

I've found what I was looking for in my previous post: it's the square-shaped thingy that appears at 19 seconds in the MegaWhat video on this page. Does anyone know what this is called? flaminglawyer 00:54, 28 January 2009 (UTC)

The device on the video at 00:19 (after the dude on the Roland drum kit and before the Coke machine) looks like the back end of some sort of digital camera. Cycle~ (talk) 01:02, 28 January 2009 (UTC)
Damn, you're right. I've been conned by my own brain! flaminglawyer 01:14, 28 January 2009 (UTC)

Diode Matrix ROM[edit]

How does a diode Matrix Rom Work? Can I construct a diode matrix only with four LED's and 9 diodes, if yes then HOW? —Preceding unsigned comment added by (talk) 04:49, 28 January 2009 (UTC)

A diode matrix ROM has multiple address lines, each of which is connected to a number of output lines using diodes. When the first address line is active, any output lines that are connected with a diode will become active. Similarly, when the second address line is active any output lines that are connected to it with a diode will become active. Here is an example circuit diagram from this project on instructables. You can easily construct the left half of this circuit using your specified materials (plus two switches and four resistors). Here is a historical example of one diode matrix ROM panel. -- (talk) 06:17, 28 January 2009 (UTC)
Wow! That takes me back. I once hand-wired a 30 byte diode matrix containing a ROM paper tape loader subroutine...ROM chips were prohibitively expensive and that was the only way to boot my hand-built Intel 8008 home computer. Debugging hand-assembled-binary software while also finding dry joints and diodes put in backwards is TOUGH! SteveBaker (talk) 02:25, 29 January 2009 (UTC)

iTunes and MP3s and WMAs[edit]

I'm fairly computer literate and I'm also a musician and a songwriter. But my girlfriend is computer illiterate. She's curious in my music and would like to add the tracks I've written and performed by myself into her iTunes library. The problem is that (in the end) she's having trouble listening to my songs on her iTuns. I recorded my songs mostly WMP but also a few MP3 files. My computer illiterate girlfriend says that she has problems importing them into her computer. (I assume because they're not in Apple's proprietary format? You knows?). So my question is actually pretty simple. How do I add songs into iTunes library if the songs are MP3s or WMAs? A Quest For Knowledge (talk) 05:14, 28 January 2009 (UTC)

As you'll see from the section immediately below, I am no Mac expert. But I think VLC media player may be your answer. -- Hoary (talk) 05:30, 28 January 2009 (UTC)
iTunes can convert from WMA to MP3 or AAC (both of which work with iTunes/iPod). A problem would only arise if you've made your WMAs with Digital Restrictions Management (DRM). And although Apple does have their own proprietary format for loseless audio, Apple Lossless, they seem to prefer AAC. --wj32 t/c 07:17, 28 January 2009 (UTC)
Well, let's ignore the issue of WMAs. There has to be a way to get iTunes to play MP3s, right? I mean, how can the world's most popular media player not play the world's most popular media format? A Quest For Knowledge (talk) 11:47, 28 January 2009 (UTC)
Why are you thinking that it doesn't? You do realize that the iTunes store recently stopped selling protected songs and is now selling mp3's? iTunes, like iPods, are 100% compatible with mp3's... as long as you converted it right. If you just took a WMV file and changed the file extension, that would be a problem. flaminglawyer 12:52, 28 January 2009 (UTC)
iTunes Store non-DRM files are still AAC, not MP3. --LarryMac | Talk 13:38, 28 January 2009 (UTC)
Well, I don't use iTunes. (I use Windows Media Player and MediaMonkey.) This is just what someone else is saying. I'm just trying to help her figure it out. Anyway, I'm downloading iTunes right now so I should be able to figure it out. Sometimes, it's hard for computer-savy people to explain to non-computer savy people how to do things on their computer so I was hoping maybe somebody already created a step-by-step guide, preferably with screenshots. A Quest For Knowledge (talk) 13:37, 28 January 2009 (UTC)
I've never had trouble getting MP3s to work with iTunes. You add them to the library (in the file menu) like you would any other kind of file. -- (talk) 00:38, 29 January 2009 (UTC)

Genuinely standalone Mac OS X installation[edit]

Last night I set up a brand new Mac 10.5 computer, straight out of the box, for a friend. She connects to the net via modem [remember those?] and plans to get a 21st-century-style net connection within days, but anyway I thought we'd get the main hardware up and running first and only then connect it to the world. So I arrived with an external HD brimming with goodies like NeoOffice and Inkscape that I definitely wouldn't want to get via modem.

No modem jack on the back. Well, no big surprise there; Apple got rid of FDDs decades ago.

What did come as a surprise was to be asked during initial setup which of four available wireless networks I wanted to use. Uh, no thanks; click return to previous screen. (Or whatever it would be called in English; by this time the computer was already talking in Japanese.) However, unless I overlooked something (and I looked very hard), there's no option to bypass selection of some conduit to the web. So, forward again. Luckily one of the wireless networks wasn't password protected so I used that. [My apologies, Mr/Ms unknown neighbor.] The connection wasn't a bad one, and I forgot how to prevent NeoOffice from updating itself to the tune of tens of megabytes.

It made me wonder, though: What's one supposed to do with no net connection during installation? Or is a net connection mandatory? The section of the Mac OS X article about hardware compatibility doesn't mention any requirement for net access. No urgency here, since I got the job done: just wondering.

(Feel free to tell me to RTFM, though I have to say that TFM is petite and seemingly full of vital stuff like reminders of the need to connect to a power supply.) -- Hoary (talk) 05:30, 28 January 2009 (UTC)

One thought: Perhaps if you chose a type of network which isn't available, it would have given you an error message, and then allowed you to retry or continue without a network connection. I agree that they should either give you an option to install without a network connection right up front or else make it very clear on the box/packaging that this is a network-only computer. Even for people who want to use it with a network, they might quite possibly want to install and test the computer first, before adding the network connection. This would be a good way to tell, for example, if it's slow because of the network connection or for some other reason. StuRat (talk) 15:49, 28 January 2009 (UTC)
It wasn't that simple. Another network had a three-letter name but required a password. First I tried a zero-length password (a stab at the enter key) and was told I was wrong, then I tried using the same three letters as the network name and was told that was wrong. No "Hey, wanna give up?" option. Well, I'm happy I could "piggyback", and I'm happier today to learn this wonderful new verb for what I did and also that "piggybacking" is only thought by some people to be a sin that will damn me to burn eternally in a vat of molten lead as cackling devils thrust their white-hot pitchforks into my sizzling flesh. (Or so I hazily recall the scenes from some rather good old paintings.) -- Hoary (talk) 16:14, 28 January 2009 (UTC)
I don't know about OS X but I know that on some Windows installs you must connect to the internet in order to register your serial number with them or something along those lines. If you can't do that, there's a number you can call in the manual and someone at the other end reads off a string of numbers that you type in to prove you called them. Or something like that. But again, that might not apply here, but I suspect there's some way to do it (for the simple reason that there are just so many imaginable situations in which you couldn't have a network connection without yet having the computer set up). -- (talk) 16:29, 28 January 2009 (UTC)
Yes, 'Doze XP and beyond, and for something like "product activation", if I remember correctly. But with OS X it was, or seemed to be, different: I wasn't given any OK from Apple ("Thank you! We've verified that your Mac isn't a Chinese knock-off! Congratulations on buying the real thing, made in Taiwan!"). Instead, there seems to be an over-eager assumption that you are connected to the world, and a desire to get this working smoothly. And I agree with the last part of what you say too. -- Hoary (talk) 01:00, 29 January 2009 (UTC)
Actually, there is a "don't connect" option built in. When the Setup Assistant gives you a list of wireless networks to choose from, instead click "Different Network Setup" (at the bottom left of the screen). This should take you to the "How Do You Connect" screen, where you can select "My computer does not connect to the internet". -- Speaker to Lampposts (talk) 22:21, 30 January 2009 (UTC)
Yes, I think that I did see [the Japanese-language equivalent of] "Different Network Setup". If I did, it didn't occur to me that "different" would encompass "no". Well thought of, Speaker! -- Hoary (talk) 03:39, 31 January 2009 (UTC)

Biggest non-white contribs to comp sci[edit]

What are the greatest contributions to computer science that have been made by non-white people? NeonMerlin 06:18, 28 January 2009 (UTC)

  • The medieval Muslims win this, hands down, for inventing programmable machines, cryptography, and the algorithm (named after Al-Khwarizmi, who first broke down computations with Arabic numerals into precise steps). See history of computer science. If you're looking for contributions to modern digital computing, though, the answer won't be as clear. rspεεr (talk) 09:05, 28 January 2009 (UTC)
    • Egyptians used cryptography 5000 years before the invention of Islam, see History of cryptography. The first known analog computer, from Greece, predates Islam by 700 years, see History of computer science. Al-Khwarizmi's name was adopted into Latin by a grammatical mistake and misunderstanding of a book title; although he was one of the mathematicians who worked on step-by-step calculations, saying that he invented algorithms is a rather gross exaggeration. Please let's keep the urban legends to a minimum. (talk) 09:38, 28 January 2009 (UTC)
      • Al-Khwarizmi wrote down arithmetic algorithms using Arabic numerals. His contemporaries should get credit too, but we don't know their names. Algorithms were named after him because he had his name on the book, even if it was a grammatical mistake.
        I am largely going by history of computer science here, in which Muslim mathematics plays what I would say is the largest role in the early history of computing. I do not mean to discount contributions made by the Egyptians, Indians, Greeks, or Chinese, or quibble over who did it first. rspεεr (talk) 19:18, 28 January 2009 (UTC)
  • Here's a place to start for modern computing: Manindra Agrawal, Neeraj Kayal, and Nitin Saxena developed the AKS primality test. For showing how to determine whether a number was prime in polynomial time, they won the 2006 Gödel Prize. rspεεr (talk) 09:14, 28 January 2009 (UTC)
You also could browse Category:Computer scientists by nationality: Category:Chinese computer scientists, Category:Japanese computer scientists, and Category:Indian computer scientists all have several members. --Maltelauridsbrigge (talk) 12:09, 28 January 2009 (UTC)

White House email[edit]

According to this article, the White House's domain is I figure the "who" stands for White House but what does "eop" stand for? Dismas|(talk) 09:44, 28 January 2009 (UTC)

That would be the Executive Office of the President of the United States, I believe. -- Captain Disdain (talk) 09:53, 28 January 2009 (UTC)

web page not updating[edit]

A website I'm viewing is not updating when I go to it. I know its updated a few times over the last few days because I've viewed it on other computers. But I am seeing a page from a few weeks ago and I can't seem to get a more up to date page. I'm guessing its a problem with my browser (firefox) but I don't know how to fix it. Thanks in advance for any help. —Preceding unsigned comment added by (talk) 11:20, 28 January 2009 (UTC)

Try Ctrl+F5 to clear the cache. –Capricorn42 (talk) 11:33, 28 January 2009 (UTC)
Or there's ⇧ Shift+F5 on some browsers, or ⇧ Shift while clicking reload. These are all browser-specific. flaminglawyer 12:34, 28 January 2009 (UTC)
In the (old) version of Firefox I'm using now, it's F5 or Ctrl-R (Shift-F5 does nothing). -- Hoary (talk) 16:18, 28 January 2009 (UTC)
That's just to reload. We're talking about clearing the cache, which is totally different. On Firefox it's Shift while clicking reload. flaminglawyer 19:31, 28 January 2009 (UTC)
I like that tag for displaying the keys... very cool - learning something new all the time. Ched (talk) 01:45, 29 January 2009 (UTC)
Me too, I didn't even realise until you said it. I kinda assumed flaming has uploaded images. (talk) 06:37, 29 January 2009 (UTC)


hi... whats meaning of the swift segment using TCP/IP? —Preceding unsigned comment added by Ramky singh (talkcontribs) 16:37, 28 January 2009 (UTC)

I'd never heard of it before but it is a TCP modification to change the method of flow control and re-establishment. Technically it's a whole new transport layer protocol designed for satelite systems. This is the primary article [1] and the abstract will give you some basic info. Shadowjams (talk) 02:09, 29 January 2009 (UTC)

sound in Firefox[edit]

Argh. Suddenly I get no sound from Youtube. (It worked before my last reboot.) What gives? I'm using Firefox on MacOS (current versions). —Tamfang (talk) 17:51, 28 January 2009 (UTC)

Might be a problem with the flash plugin, try re-installing here —Preceding unsigned comment added by (talk) 21:29, 28 January 2009 (UTC)
No luck. I do still get sound in movies from some other sites. —Tamfang (talk) 21:22, 3 February 2009 (UTC)

Calculating values that add up to a given sum in Excel[edit]

Hi, I have a question about MS Excel, and while I suspect the answer is "It can't be done", I figured I'd at least try.

My problem is this: Say I have a large group of numbers, and I need to know if there is a combination of them that add up to a specified separate number, is there an easy way to do this?

For (a really simple) example, let's say I have the following numbers:

1, 3, 10

and I need to know if any of them add up to 13. Is there a formula (or other method) I can use that will give a 'True' value for this? My list of figures is pretty huge, and so I suspect this may be beyond Excel's capabilities (it would have to, I imagine, calculate the sum of every combination of two or more numbers and try and match them to my specified number(s)), but even a long shot is worth a try, right? Any assistence would be gratefully received. Phileas (talk) 17:54, 28 January 2009 (UTC)

This may be of at least some interest to you. Cheers,—Ëzhiki (Igels Hérissonovich Ïzhakoff-Amursky) • (yo?); 18:14, January 28, 2009 (UTC)
See here and related message board thread here. Mike R (talk) 18:23, 28 January 2009 (UTC)
See also here. Mike R (talk) 18:27, 28 January 2009 (UTC)

Excellent! That's great! Thanks for your help! Phileas (talk) 19:14, 28 January 2009 (UTC)


Perl, regex, distinct matches[edit]

In Perl, you can store the regex matches into an array.

Can Perl only store distinct matches? I mean it may act like SQL's SELECT DISTINCT * FROM blah.

For example, I want to store all distinct words (no numbers) of an article into an array. I may use the array of distinct words for other purposes. -- Toytoy (talk) 18:12, 28 January 2009 (UTC)

Have you tried searching Google? Generally, hashes enforce distinct values; arrays do not (though they can be post-processed). – 74 18:51, 28 January 2009 (UTC)
Idiomatic Perl for getting distinct values would look like:
$hash{$_}++ for split ' ', $article;
my @distinct_words = keys %hash;
--Sean 20:08, 28 January 2009 (UTC)