Wikipedia:Reference desk/Computing

From Wikipedia, the free encyclopedia
Jump to: navigation, search

The Wikipedia Reference Desk covering the topic of computing.

Welcome to the computing reference desk.
Shortcut:
Want a faster answer?

Main page: Help searching Wikipedia

How can I get my question answered?

  • Provide a short header that gives the general topic of the question.
  • Type ~~~~ (four tildes) at the end – this signs and dates your contribution so we know who wrote what and when.
  • Post your question to only one desk.
  • Don't post personal contact information – it will be removed. We'll answer here within a few days.
  • Note:
    • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
    • We don't answer requests for opinions, predictions or debate.
    • We don't do your homework for you, though we’ll help you past the stuck point.


How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

  • The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
 
See also:
Help desk
Village pump
Help manual


June 24[edit]

Can the Internet be interrupted by the government to broadcast emergency announcements?[edit]

In the same way TV and radio broadcastings are interrupted to send active alerts, in cases of inclement weather, natural disasters, or any emergency. The Internet has become the main medium of communication for many, taking the place that TV and radio were occupying in the past. It should be the medium of choice for important messages.--Yppieyei (talk) 13:19, 24 June 2015 (UTC)

The internet is not under the direct control of any single entity. It is not a broadcast medium. It is a request/response medium. So, no. With the current design and structure, the government cannot force a message to appear all over the internet... unless they post it on Facebook as an animated GIF with Deadpool riding Pinky Pie while making some statement like "There's a threat of severe thunderstorms with tornadoes over Oklahoma from 6pm to 10pm. Share if you love God. Like if you love your Mom. Ignore this if your are evil and want everyone to die, you scumbag!" 199.15.144.250 (talk) 13:52, 24 June 2015 (UTC)
Cell phone networks aren't broadcast networks either, but there are systems in place to send emergency alerts (such as Wireless Emergency Alerts in the US). The Internet protocol supports multicast which can in principle be used to efficiently send a packet to every Internet-connected machine (though with no guarantee of delivery). There could in principle be an RFC defining an IP-based emergency alert system. There just happens not to be. It has nothing to do with the design of the Internet. -- BenRG (talk) 18:26, 24 June 2015 (UTC)
That is not correct. Cell phone networks *ARE* broadcast networks. To function, your phone is always listening to the cell tower. Your computer is not always listening to the Internet. It only listens on a specific port to get an answer to a specific request and then it hangs up. 199.15.144.250 (talk) 18:40, 24 June 2015 (UTC)
Broadcast means that everyone gets the same data, not that everyone is always listening for data. Internet-connected computers do always listen for incoming packets. -- BenRG (talk) 07:31, 25 June 2015 (UTC)
I thought we were discussing networking. Broadcasting (networking) is not the same definition. You can rationalize that track data communications and packet data communications are one and the same. If you insist on believing that, there is nothing I could ever say to make you change your mind. Perhaps you will work on cell phone towers some day and realize how "broadcast" greatly differs from computer networking. 199.15.144.250 (talk) 13:55, 25 June 2015 (UTC)
Which government ? Which country ? Don't forget that the internet is a global infrastructure, not local or national. Can you think of any situation that would need a message to be broadcast to every person with an internet connection anywhere in the world ? Gandalf61 (talk) 13:54, 24 June 2015 (UTC)
That could be done in principle, because it is possible for internet service providers to intercept web browser requests and return any information they want to. But setting up a system would mean getting all ISPs to cooperate, in the same way that the Emergency Alert System requires all radio broadcasters to install and maintain the necessary equipment. I'm pretty sure no such system currently exists. Probably the most useful thing the government could do, if it felt such a system to be necessary, would be to ask for cooperation from Google and other search engines, so that they could return an emergency warning along with their search result. In fact such a system already exists, in the form of Google Public Alerts. Looie496 (talk) 14:35, 24 June 2015 (UTC)
Yes, it is theoretically possible, depending on the country, although the mechanism would be quite different than it is for broadcast media.
Look at this map (the site uses old data, but illustrates the point).
In the United States, it would be particularly difficult as it has far more ISPs than other countries (fewer now than in 2003, I imagine, but still more than anywhere else). On the other hand, many countries have only one, two, or three. In such a case it would be easier for a government to set up infrastructural interventions (which is why the Great firewall of China is possible).
The other way it could be done is on the level of personal computers or local networks. Take for example (using China again), Green Dam Youth Escort. The plan was to require any computer sold in China to have this content-control software on it that would monitor Internet traffic. Assuming an Internet connection, it would be pretty straightforward for there to be a centralized location that could send messages using such software (or other preloaded software). — Rhododendrites talk \\ 14:50, 24 June 2015 (UTC)
The question was about the Internet, not the Web. I interpret that as popping up a message on the desktops of Internet-connected machines even if they're using a word processor at the time. It would certainly be possible to do that, if there were a standard for it, and legislation forcing vendors to implement it.
Implementing an emergency alert system by spoofing web pages is a terrible idea, and I would hope no country would seriously consider an alert system that worked that way. -- BenRG (talk) 18:26, 24 June 2015 (UTC)
If you want to pop a message up on a desktop based on an Internet-based message, you *MUST* have a program running on the desktop that is always listening for the message. That means that you have to force everyone to install the alert client software (which must be programmed to run on a multitude of different desktop systems). Then, you have to have them constantly listening on the network - which computers do not normally do. The Internet is TCP/IP-based. It is designed to make a connection, send a request, get a response, and then hang up. It is not designed to listen forever and ever. So, you have three huge obstacles: 1) The software you want doesn't exist. 2) People won't want to install it and most will remove it if it comes on the machine. 3) Computers aren't designed to use the Internet in that way. Of note: There is one way in which this has already been developed and is in use: Bot networks. In a bot network, computer users ignorantly install the client on their computer. The client connects to the server and listens and listens and listens - forever. Then, the server sends a message to the client. The message causes the client to send out tons of spam or do a DOS attack on a server or something like that. So, in one way, you could ask: Why doesn't the government force everyone to join the Federal Bot Network or go to prison? 199.15.144.250 (talk) 18:49, 24 June 2015 (UTC)
This is partly true, but the problem isn't quite as hard as this makes it seem. Every computer that is connected to the internet and has an IP address is supposed to listen for Internet Control Message Protocol packets (which include a type of packet commonly known as a "ping") and respond to them immediately. This is part of the networking standard. In fact it is usual for networked computers to listen constantly to a set of "port"s -- that's the reason firewalls exist. There is actually one port, number 533, known as "netwall", that has been officially designated for emergency broadcasts (see List of TCP and UDP port numbers), though as far as I know no system makes use of it. So much of the functionality needed to set up something like this already exists. Looie496 (talk) 21:56, 24 June 2015 (UTC)
Netwall is not implemented in any OS I've used. Further, it is UDP. I'd make a UDP joke, but you probably won't get it. 75.139.70.50 (talk) 01:37, 25 June 2015 (UTC)
I got it, but it's become a TCP joke because I just said that MChesterMC (talk) 08:18, 25 June 2015 (UTC)

What is URL Canonicalization?[edit]

I want to know what is URL Cannonicalization? — Preceding unsigned comment added by Genelia.Abraham (talkcontribs) 13:34, 24 June 2015 (UTC)

It's a way of changing website addresses - mostly removing funny-characters - so they're more consistent. See URL normalization. 82.152.145.136 (talk) 13:58, 24 June 2015 (UTC)

It is more commonly called URL normalization. The purpose is to normalize the URL so you can compare two URLs to see if they are the same. Imagine if I tried to impress you by giving you links to twenty different sites, but with URL Canonicalizatin, you normalize them and find out that they all point to the same page. 199.15.144.250 (talk) 13:57, 24 June 2015 (UTC)
See canonicalization. The basic concept is that when there are different ways to write something, but the meaning is the same, one particular version is chosen as "canonical". In math, 5/2, 10/4, , 2.5, and 2.5000 are all representations of the same number and are precisely equivalent (see note), but unless someone is trying to make a specific point they will use only one of those forms, the one they consider canonical (although I think different people will disagree as to which one that is). (Note: in science and engineering, forms like 2.5000 have a different meaning as they indicate that more significant digits are known. In math, numbers are presumed to be exact.) --70.49.171.136 (talk) 19:18, 24 June 2015 (UTC)
URL normalization and URL canonicalization are not the same thing. The issue is confused by the fact that before the Canonical link element was added to HTML, the two terms were often used interchangeably; I just corrected a couple of out-of-date Wikipedia pages.
URL canonicalization is It is described in RFC 6596 (2012). It specifies the canonical/preferred version of a web page[1][2][3] --Guy Macon (talk) 21:18, 24 June 2015 (UTC)

wordpress theme[edit]

1) I want a wordpress theme with home page which only contain different category widget with link to different article, just like apuzz.com ?123.238.96.132 (talk) 17:44, 24 June 2015 (UTC) — Preceding unsigned comment added by 123.238.96.132 (talk) 17:36, 24 June 2015 (UTC)

2) how to get good backlink for website for free ??123.238.96.132 (talk) 17:44, 24 June 2015 (UTC) — Preceding unsigned comment added by 123.238.96.132 (talk) 17:38, 24 June 2015 (UTC)

3) is it worth learning bootstrap ?123.238.96.132 (talk) 17:44, 24 June 2015 (UTC) — Preceding unsigned comment added by 123.238.96.132 (talk) 17:39, 24 June 2015 (UTC)

I added numbers to your Q's StuRat (talk) 19:11, 24 June 2015 (UTC)
  • Woulda been even more useful to add section headers. —Tamfang (talk) 06:24, 27 June 2015 (UTC)
1) If you are using Wordpress, you really shouldn't be concerned with questions 2 and 3.
2) People will link to your website if it has something useful. Think about content before you think of design and marketing. For example, XKCD is popular because of the content, not because it looks cool and the owner paid a lot of people for backlinks.
3) Why learn Bootstrap if you are committing to using Wordpress? Just let the template writers do it for you and complain that the template doesn't meet your very particular requirements.
4) What happened to question 4: How do I get insanely rich by slapping together a Wordpress site and hoping everyone rushes to it and hands over gobs of money!? 199.15.144.250 (talk) 19:26, 24 June 2015 (UTC)
1 - are you using WordPress the software you install on a web server yourself or WordPress.com the blog-hosting site? They use different themes.
2 - the fields of search engine optimization (even though it's not strictly search engines you're talking about) and Internet marketing deal with that question quite a lot, and there's no single easy answer. the above response, while likely obvious, fits within the more ethical approaches
3 - depends what you want to do? If you don't already know html, css, and how wordpress works, you'll have a hard time doing anything with bootstrap. People do sometimes use bootstrap as part of some wordpress themes, but this article suggests it may not actually be a great fit (it's definitely popular though). If you do already know the basics, then learning Bootstrap would give you a transferable skill with applicability beyond wordpress.
(since it hasn't been linked here so far, here's our article on it: Bootstrap (front-end framework)) — Rhododendrites talk \\ 21:46, 24 June 2015 (UTC)

Hack for S3 galaxy mini to extract raw data from the camera sensor?[edit]

My smartphone software only saves jpg files, but obviously this is obtained from the raw data from the camera sensor that is not saved. However, it seems to me that it should be possible to hack the software that is involved in image processing so that the raw data from the sensor will be saved without any of the processing to produce jpg files. I could then download the data to my PC and do the demosaicing, noise reduction, color management etc. using my own programs which should yield much better results. But I didn't find any hacks for rooted S3 galaxy mini smartphones for this purpose. Count Iblis (talk) 22:09, 24 June 2015 (UTC)

This is sort of a Russell's teapot problem: rather than speculating that such software does exist, and asking us to find it... the onus is on you to show that such software does exist.
It has been my experience that most consumer devices are not user-friendly enough, nor fun enough, for enthusiast hackers to spend a lot of effort reverse-engineering. (I make this statement with full awareness that enthusiast hackers can be very skilled and very tenacious.) The complexity of a modern digital camera is just a few notches too high for amateurs or hobbyists to break into. A notable exception is the Nokia 900: but that one had commercial sponsorship, corporate cooperation, and a team of highly capable graduate-students!
On the flip-side, many programmable camera kits are available commercially at reasonable price points amenable to the various capabilities you can find on new hardware. Would you like help tracking down such a development board?
Nimur (talk) 23:13, 24 June 2015 (UTC)

Android has a programmable interface for accessing the camera[4] that includes a couple of raw type formats [5]. Though I do not know if S3 galaxy supports it. Graeme Bartlett (talk) 23:25, 24 June 2015 (UTC)

Samsung's Camera SDK - and the Google Android RAW10 ImageFormat - requires API Level 21 (first available in "Android Lollipop"); the S3 Mini does not support this API level.
In other words: the manufacturer has chosen not to expose "raw" sensor data to the users! This is probably why our OP is asking about "unofficial" mechanisms to access such data.
Nimur (talk) 00:21, 25 June 2015 (UTC)
If it was first provided in in Lollipop I don't know if you can say they chose not to expose raw data to the users so simply. Lollipop came out long after the S3 Mini release and Samsung had abandoned new firmware support for S3 Mini by the time of its release, as they and many other manufacturers do after 2 years or less. In other words, the decision not to provide Lollipop was likely for a whole host of reasons, raw support may not have been considered at all.
Now technically they could have provided their own API for raw support, as they did for a number of other things which Google didn't initially support and for some things which Google did support but they wanted to do via another method. So by that token you could say they choose not to provide raw sensor data, still it's a more subtle point when the framework of the OS they are using doesn't provide it already.
Anyway as is common with most popular phones, there are unofficial Lollipop releases for S3 Mini. Some of these even support the camera. E.g. [6]. Whether these provide RAW support I don't know.
Nil Einne (talk) 02:53, 25 June 2015 (UTC)
Hmm thought I posted this yesterday but guess I didn't save. I meant to say I'm not that sure the S3 Mini unofficial Lollipop releases would provide RAW support. While finding the right drivers etc for the camera with source is often problematic, hence why camera support is often an issue for unofficial releases, I'm not sure that whatever they do generally provides the low level access needed for RAW support. Also I didn't mention this but if you do want hackiness with phone cameras your best bet is probably to look for a phone known for the extremely high quality camera. These are the ones that tend to get enthuasist interest. Nil Einne (talk) 02:00, 26 June 2015 (UTC)
Thanks! I'll see if I can install the Lollipop release for the S3. Count Iblis (talk) 18:19, 25 June 2015 (UTC)

June 25[edit]

Are Communications protocols languages too?[edit]

Is calling them "protocol" just a kind of convention, or even a misnomer? Couldn't we talk about "communication languages" and "programming languages"? That would reflect the analogy between both (as they say, " protocols are to communications as programming languages are to computations"). If they are not, what would they need to be a language?--Yppieyei (talk) 06:57, 25 June 2015 (UTC)

I think the difference is that formal language theory has no concept of a conversation. A protocol is not just a set of valid sentences and their meanings (a language) but also a set of rules about which sentences can be replies to which other sentences. -- BenRG (talk) 07:43, 25 June 2015 (UTC)
Correct. It would be improper to refer to a communication protocol as a language. It is more proper to refer to the protocol as a set of rules that contain a language. 199.15.144.250 (talk) 13:35, 25 June 2015 (UTC)

What's the model number of Xiaomi's latest router?[edit]

What's the model number of Xiaomi's latest router[7]? Officially they're just calling it the MiWiFi, which isn't very helpful since that's the exact same name they gave the previous router, so when I google "Xiaomi MiWiFi how to install openwrt" it's all tutorials about the previous version. Is there a model number with which I can differentiate the new router? For the previous model it was "R1D". My other car is a cadr (talk) 15:08, 25 June 2015 (UTC)

Probably the most meaningful way to distinguish the new router is via the chipset (Broadcom 4709C) and FCC ID (most devices have one). Perhaps also the unique feature (6TB). Nil Einne (talk) 01:54, 26 June 2015 (UTC)
Thank you very much for the help. My other car is a cadr (talk) 15:15, 26 June 2015 (UTC)

June 26[edit]

Strange (possibly fraudulent) phone call[edit]

I received a phone call on my land line this afternoon, which caller ID said was coming from area code 404, which is greater Atlanta. The person said that he was calling from Microsoft engineering, and needed to talk to me about my Microsoft Windows computer. He said that they were getting messages from my computer about its files, and that I had a problem with my files, and they asked me if I would sit down at my computer so that they could help me. I didn't entirely understand what they were saying was wrong, but they were saying that my computer was either using a lot of resources or that it was using a lot of files, or something. I said that I had not gotten any email from them, and that they should contact me by email if they really were legitimate. He said that they only used email to test, and that when they actually determined that there was a problem, they just phoned and asked me to sit at the computer. He continued to say that he was only trying to help me. I said that, since I didn't know who he was, I wasn't going to give him access to my computer, because he might be trying to install a keystroke logger or spyware. He insisted that he was only trying to help me. Eventually I asked if I should call either the police or the Federal Communication Commission. I wound up hanging up. Robert McClenon (talk) 01:56, 26 June 2015 (UTC)

The first sign that something might be wrong is that, when I answered, he didn't ask for me by name, and, if he really was receiving trouble reports from my computer, it would have provided some information, such as, at least, the name of my computer, and maybe the email address used in Outlook on the computer. Robert McClenon (talk) 01:56, 26 June 2015 (UTC)

My question is whether this is a known scam/problem, or whether this is something new. What was the caller trying to do? Was he calling land-line phones randomly, or getting my number from some list? What was he trying to do? Robert McClenon (talk) 01:56, 26 June 2015 (UTC)

Scam: [8]. AndyTheGrump (talk) 01:59, 26 June 2015 (UTC)
These are common enough that we even have an article Technical support scam and Microsoft themselves have a warning page [9], as well as the usual suspects [10] [11] [12] [13] [14]. AFAIK most of these are operated from outside the US in places known for cheap call centres particularly India. In the VoIP world the area code can easily be meaningless. [15] [16] does mention some US companies, but it sounds like these are websites rather than cold callers, and in any case whatever the wisdom of setting up a company like that in the US, it doesn't say much about where their call centre is. (The second source does mention some calls with a US area code.) You can see some examples of people engaging with such callers here [17] [18] [19] Nil Einne (talk) 02:15, 26 June 2015 (UTC)
I got one of those calls a few weeks ago. He said that my Windows computer was having issues, so on and so forth. I just laughed. The computers in my house run either Mac OS X or Linux. Never Windows. Good job keeping your head about you when they called! Dismas|(talk) 02:46, 26 June 2015 (UTC)
My parents get them at least once a week: they have never owned a computer. {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 13:07, 26 June 2015 (UTC)
  • A month ago, when "John from Windows Support Center" announced himself, I cheerily asked him to tell me more about Windows Support Center. He immediately hung up. — Sometimes I'm tempted to fire up my Windows virtual machine and follow instructions to see what happens, then restore the VM from backup. —Tamfang (talk) 06:30, 27 June 2015 (UTC)

Not answered[edit]

Thank you. My original question has not really been answered, except that everyone agrees that it was some sort of scam. What exactly was he trying to do? Was he trying to turn my computer into one of his zombies? By the way, I am essentially certain that the call was coming from area code 404 (and that could be a bad pun), because I don't think that calls from outside the United States are able to spoof area codes. Was he randomly calling land lines? Robert McClenon (talk) 15:20, 26 June 2015 (UTC)

It's answered in the paragraph beginning "The scammers then perform questionable tasks to "repair" the system" in Technical support scam. -- Finlay McWalterTalk 15:31, 26 June 2015 (UTC)
Okay. Perform questionable tasks, such as turn the computer into one of his zombies. Robert McClenon (talk) 15:41, 26 June 2015 (UTC)
And steal your email credentials, empty your bank account, buy stuff on your Amazon account, and get enough personal information on you to take out credit in your name. Congratulations, you now own a speedboat in Macao. -- Finlay McWalterTalk 15:47, 26 June 2015 (UTC)
The Caller ID spoofing article confirms what Nil Einne said - spoofing callerID is easy, particularly on VOIP, and your essential certainty that the call was from area code 404 is entirely misplaced. -- Finlay McWalterTalk 15:47, 26 June 2015 (UTC)

I have another comment. This caller was stupid as technical support scammers go, although maybe all technical support scammers are stupid. He didn't have the sense to give up and move on to another victim when I said that he was trying to install a keystroke logger. At that point he should have known that he wasn't going to succeed, but maybe all technical support scammers are too stupid to figure out whether they are going to succeed, and just keep on trying. Robert McClenon (talk) 15:26, 26 June 2015 (UTC)

He didn't have the sense to move on, but maybe technical support scammers don't have the sense to move on, because maybe they have enormous egos and enormous confidence in their own power of persuasion and social engineering. Robert McClenon (talk) 15:41, 26 June 2015 (UTC)

Every minute you stayed on the call with him was a success for him. When he cold called you, he didn't know it was a domestic residence - now he does. He didn't know there was a computer there, now he does - and you probably confirmed to him that in runs Windows, and probably what version. In these kind of circumstances people try to refute the con-man's assertions with facts - "that can't be, we have a new AVG pro installation"; "my son set this computer up - he's very good with things like that" or partial confirmations "we have had trouble connecting to comcast"; "ESPN hasn't been working today - is that connected?". Even your threats tell him something "I'll call the FCC!". And the fact that you stayed on the line with him (for what sounds like 10 minutes or more) tells him you're susceptible to this kind of scam. He can sell this information, or pass it to a colleague who is far more credible sounding. So if you get a call in a couple of months from Comcast, or AVG's tech support, or the FCC's phone scam investigation department, from a professional sounding American lady with a DC area code, there's a greater chance of it working. -- Finlay McWalterTalk 16:17, 26 June 2015 (UTC)
I don't understand. What are you saying I should have done differently? Robert McClenon (talk) 17:06, 26 June 2015 (UTC)
The fact that it isn't obvious is the problem. You did not gain anything by talking on the phone. You will likely get more calls now that you have proven that you are willing to talk. What should you do? Hang up. 209.149.113.97 (talk) 17:21, 26 June 2015 (UTC)
When it became clear that they didn't know your name, you should have put the phone down on them. There's a great deal to be said for letting all calls from unrecognised or withheld numbers go to voice mail - genuine callers will leave a message, telesales and scammers mostly won't. I think about 95% of the calls I get, that aren't from individual people I already know, are some species of junk. -- Finlay McWalterTalk 17:26, 26 June 2015 (UTC)
Their main target are the large numbers of old people. In today's world you can hardly do without a computer with internet access. If you had little experience with using computers and the internet all your life until the age of 85 and have only recently started to do online banking, then you are an easy target for these scammers. So, it could be that Robert's voice or the way he talks makes him sound like an old person. Count Iblis (talk) 18:27, 26 June 2015 (UTC)

Creepy i.p. storage[edit]

I have used various wikimedia projects for roughly 8 years as an i.p. This year is the first time I regularly see my i.p. being remembered. For example edits I made 3 months ago show up in my i.p. history. In other words I regularly get the same i.p. I used ages ago. I feel uncomfortable with this and would like to know why its happening. I feel like wikimedia has my computer stored on their devices and am freaked out and scared by that. Help.84.13.27.150 (talk) 16:44, 26 June 2015 (UTC)

Wikimedia does not control what IP is assigned to your computer. Your ISP does that. If you don't like getting the same IP you used to use, switch to a different ISP. 209.149.113.97 (talk) 17:00, 26 June 2015 (UTC)
A list of your contributions can be seen here: [[20]]. Wikipedia does not have a lot of information about you. Besides the fact that you are in London, there is not much tha can be extracted from that information. --Yppieyei (talk) 17:24, 26 June 2015 (UTC)
Just to be more specific, the IP address doesn't give out information about the user. What the user submits could be different. If I used this IP to post that I am a prisoner in Edgefield and I want help on the paper I'm writing for my BS degree at Furman, then it would be MY fault that I posted information about myself, not my ISP-assigned IP address. 209.149.113.97 (talk) 17:41, 26 June 2015 (UTC)
Yeah - the IP address DOES give out information that anyone can find...specifically, you can find the name of the ISP the person is using...which generally also tells you roughly where they are in the world (which is how Yppieyei knows you're probably in London). Creating an account hides that information - so ironically, you have more privacy if you create an account than if you don't. If you're really concerned about privacy, you should worry that knowing your IP address (at least for a few hours after you post) would give a hacker the ability to go and attack your computer remotely...which is why I have always edited here with an account name. SteveBaker (talk) 00:52, 27 June 2015 (UTC)
What's going on here is that your computer almost certainly doesn't have a single IP address that you are personally assigned. There aren't enough unique IPv4 addresses available in the world for many ISP's to give everyone their own. So they are shared. When you turn your computer on, it doesn't know what it's IP address is - so it uses a special protocol called "DHCP" to request an IP address from your ISP's computer. Once your computer has an IP address, it uses it to talk to Wikipedia - and that's what Wikipedia stores for your edits and signatures. The detail that matters here is that your ISP's computers can implement the DHCP protocol in many different ways - there are no hard-and-fast rules about that.
Some ISP's give you a different IP address every time you turn your computer on. Some others give you a new IP address every few hours. Yet others go to the trouble to try to always give you the same address you had the last time...but without any kind of a guarantee that it'll be available. These numbers may be selected from a relatively small pool (maybe just a hundred or so addresses that differ only in the last number) - or they may come from a pool of millions of addresses. But these days, most ISP's try to give you the same IP address every time you turn your computer on - they won't always succeed, but they quite often try.
So if your ISP handed out IP addresses at random from a large pool, the odds are small that you'd see your own edits in the edit history for whatever IP address you're currently using...but if they then switched their DHCP policy to the approach where they try to give you the same address every time - or to selecting from a small pool - then you could go for months without seeing a different address pop up and you might see the same handful of addresses popping up over and over again.
You're not going to be able to change how your ISP allocates addresses via DHCP - so (as others have said), you'd have to switch to an ISP that uses a different policy. It would likely be very hard to find out what their policy is in advance...it's not the kind of thing that their sales or tech support people are likely to be very knowledgeable about.
If you're relying on randomly assigned IP addresses for some kind of security/privacy reason...that's an entirely unreliable proposition and you're basically screwed. As IPv6 gradually replaces IPv4, the number of IP addresses available increases spectacularly - and it's much more likely that your ISP will keep the same address for you indefinitely because most people who care prefer it that way.
SteveBaker (talk) 00:47, 27 June 2015 (UTC)
With a normal home broadband installation, it's more likely that the computer itself would get its (private) IP address using DHCP from the user's local router/modem. The modem would probably be a cable or DSL modem, and it would get the public IP address from the ISP with either PPPoA or PPPoE.--Phil Holmes (talk) 10:49, 27 June 2015 (UTC)

Why pdf files do not use Unicode?[edit]

According to Portable_Document_Format#Encodings, in pdf files "characters are shown using character codes (integers) that map to glyphs in the current font." Wouldn't that imply that you always have to embed the font in the document, or hope that it's already installed in the user's machine? Why not use Unicode? --Yppieyei (talk) 17:22, 26 June 2015 (UTC)

Fonts
My understanding is that PDF files are mainly intented to represent printed paper documents and have the exact same appearance in every viewer. My understanding is you do normally embed the font (or a subset of the font containing the glphys the document actually uses), or hope the specified font is already installed on the user's computer.
The second sentence of Portable Document Format says "Each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, graphics and other information needed to display it." I assume "fixed-layout flat document" means something like "represents a printed paper document and has the exact same appearance in every viewer".
Unicode
In most PDF files, you are able to select the text, copy it, and paste it in other programs, so I assume the PDF file also stores some standard character code (maybe Unicode) for the copy-and-paste ability.
The section you linked to (Portable Document Format § Encodings) seems to describe PDFs normally use an encoding based on Windows or Macintosh OS and says "For large fonts or fonts with non-standard glyphs, [...] it is necessary to provide a ToUnicode table if semantic information about the characters is to be preserved." So it sounds like Unicode may be used for textual copy-and-paste ability.
--Bavi H (talk) 00:11, 27 June 2015 (UTC)
But if the file stores integers representing glyphs of the font (which is embedded) and includes a Unicode representation, you'll end with redundant information in it, at least in this concrete case, where you want to allow copy-and-paste, for example. What could affect the appearance if you had Unicode only + the embedded font in the file? --Yppieyei (talk) 00:35, 27 June 2015 (UTC)
PDF predates the wide adoption of Unicode by years, and it borrows a lot from PostScript, which predates Unicode 1.0 by a decade. That's the only reason, I think. -- BenRG (talk) 00:58, 27 June 2015 (UTC)

How to align a div[edit]

i want to align the div which inside another div to center, how to do that ??123.238.96.132 (talk) 18:01, 26 June 2015 (UTC)

like this
margin-left: auto; margin-right:auto; being the important thing. -- Finlay McWalterTalk 18:28, 26 June 2015 (UTC)

June 27[edit]

fetching data from database using ajax[edit]

i have a php page in which i have written one mysql query for fetching result and displaying on the page, there are various buttons on the page on click on each button i want to make a ajax request and pass the value of variable to mysql query and base on that variable i want to fetch result from database, without reloading the page.09:23, 27 June 2015 (UTC)106.51.131.180 (talk)

Typically would have an additional url served by your php (called something like http://example.com/myapp/mydata). That runs the SQL query, but instead of emitting HTML with the result, it encodes the result in a readily parsible format like JSON or XML. JavaScript on your page requests that url (with XMLHttpRequest, which despite its name can get JSON or text or whatever too), parses the data and generates the corresponding DOM elements. Depending on the structure of your site, you might keep the same base url for the html and json data, and have the client communicate which you want using options in the query string - so http://example.com/myapp gets yields html, but http://example.com/myapp?format=json yields json data instead. -- Finlay McWalterTalk 12:57, 27 June 2015 (UTC)

Can a program generate a grammar from a series of texts?[edit]

Can a program generate a grammar from a series of texts? — Preceding unsigned comment added by Scicurious (talkcontribs) 15:53, 27 June 2015 (UTC)

Do you mean text in a natural language. Ruslik_Zero 17:36, 27 June 2015 (UTC)
Yes, an example of such a program for a natural language would be an interesting answer. However, I wonder whether a program can generate a grammar for any formal language, if it gets enough samples. --Scicurious (talk) 18:24, 27 June 2015 (UTC)
Grammar induction is the article. -- BenRG (talk) 19:35, 27 June 2015 (UTC)
Anything that a human can do can in principle be done by a sufficiently sophisticated program. So as a question of principle, the answer is yes. At a practical level, the answer is that it depends on the complexity of the grammar and the nature of the sample. Looie496 (talk) 11:46, 28 June 2015 (UTC)
In computer science a Formal grammar is a definition that allows recognition of a language. Grammars deduced from examples have the problems of false positives and false negatives. You can generate a grammar for your sample that has no false positives when given an example not in the sample you based the grammar, but it will accept no sentences that aren't in the sample, which is kind of useless. You could also make a grammar that will accept anything, having no false negatives by rejecting strings you would want, but since it accepts anything it is also pretty useless. If you try a grammar somewhere in between it will likely have BOTH false positives and negatives as it rejects some things you'd want to include and accepts some things you don't want. Unless you have a sample containing every valid string in the language you'd be unable to make a perfect grammar. In practice, you might be able to get close to the right grammar, but you wouldn't be able to prove it was right without either a complete list of correct strings in the language or a correct grammar. (So, can't say it wouldn't be useful in practice, but no guarantees.) RJFJR (talk) 14:33, 28 June 2015 (UTC)

Why HD audio have higher sample rate?[edit]

My teacher said that using a sample rate of 44.1Khz for audio recording is enough as 44.1Khz > 2*20Khz. 20Khz is the high the frequency that we can hear, so according to Nyquist–Shannon sampling theorem nothing is lost. So why HD audio use a sample rate up to 2.8224 MHz? — Preceding unsigned comment added by Hunsu (talkcontribs) 17:50, 27 June 2015 (UTC)

Intel High Definition Audio, which is what a lot of people call "HD Audio", goes up to 192 kHz; Direct Stream Digital samples at 2.8224 MHz, but that's only 1 bit per sample, whereas CD-DA is 16 bits per sample (and IHDA can go to 32 bit). This article goes into some length discussing the diminishing returns of higher data rates beyond CD-DA's. -- Finlay McWalterTalk 18:27, 27 June 2015 (UTC)
That article is quite good.
2 × 20 kHz is enough only if the waveform is infinitely long and you interpolate with a sinc filter, which would take forever (literally). With the more practical filtering of actual audio hardware, you need a somewhat higher sampling rate (like 44.1 kHz). -- BenRG (talk) 20:03, 27 June 2015 (UTC)
Audio fanatics will very often claim to be able to hear frequencies up above the 20kHz range and use this as a reason to reject modern digital music. The problem is that these people are notoriously bad at doing double-blind testing of their claimed abilities. However, since those are generally the people doing the reviewing of audio equipment, it's possible that manufacturers and standards organizations would push the specification up above the true limits of human hearing just to get better reviews. Higher frequency audio bandwidths are childishly easy to reproduce these days - so pushing the specification even higher above the human range is a very low cost thing to do.
As I've said here several times in the past, the world of audio enthusiasts has become a very sad and unscientific place. Note the $10,000 USB and Ethernet cables sold to exceedingly stupid/gullible people on grounds that they'd improve digital sound quality - and reviewers of said cables enthusiastically proclaiming better "presence" or "ambiance" (whatever the heck that is!) in the resulting sounds...even though it is quite clearly impossible for that to be the case when these cables are transferring purely digital data. SteveBaker (talk) 16:09, 28 June 2015 (UTC)
But the 1's and 0's are so much fatter and deeper when using platinum plated gold connector cables with diamond inlay! 209.149.113.185 (talk) 17:49, 29 June 2015 (UTC)

Printing text[edit]

Dear Sirs..

When typing a letter ( black) are you using any ink from the color cartridge?

In other words ,can I just reload all black?. Hewlett PackardPSC 1100/1200 Thankyou ```` 2602:306:B861:2A0:AD53:9520:D678:4F32 (talk) 20:19, 27 June 2015 (UTC)

See the section of this document called "Some color ink may be used when printing black text-or-graphics". It says that IPH (integrated print head) printers can print without color ink, but IIC (individual ink cartridge) printers can't. I don't know which category the PSC 1100/1200 are in. -- BenRG (talk) 22:06, 27 June 2015 (UTC)
I have a PSC 1200, and it has a color cartridge and a black ink cartridge, if that helps. StuRat (talk) 22:08, 29 June 2015 (UTC)
Note, ink printers need to clean the print heads. When moving the print heads off from parking position, the ink beginns to dry. This requires to flush the ink heads by time. --Hans Haase (有问题吗) 20:17, 30 June 2015 (UTC)

June 28[edit]

PHP[edit]

i have included header of the page using "<?php include 'header.php' ?>" in one php file, i want header not to reload whenever i click on any option on header. how to do it exactly ? 106.51.131.180 (talk) 06:30, 28 June 2015 (UTC)

You must use AJAX and dynamically update the content section of the page. You could use frames - but that's so 90's. If you waste time trying anything but AJAX, everyone will laugh at you. 75.139.70.50 (talk) 19:29, 28 June 2015 (UTC)

How to kill a frozenbird[edit]

I decided to give Ubuntu a chance. "Oh, it's quite stable. You won't want to use Windows again", they told me. However, every now and then a program freezes the system. Sometimes Ctrl + Alt + F3 will take me to a tty and I am able to kill the infringing program, or to kill all with kill -9 -1 and log-in again. Sometimes a terminal can be launched with Ctrl + Alt + t, and xkill be run. Sometimes a compiz --replace or a unity --replace will deal with the problem (I have the impression it's all compiz's and unity's fault, but they might be innocent). Sometimes, though, the system is completely blocked and none of the solutions above will work. That means, no access to any terminal.

Is there a way of always having the possibility to run a command to kill a program or run unity/compiz --replace? Could I for example, make the computer "earmark" some resources just in case the user wants to kill something? Is there something that will always work? Otherwise, I don't see how Ubuntu could be more stable than Windows. It's a pity actually, since I am enjoying some aspects of it (like installing programs from the repository). --Llaanngg (talk) 17:45, 28 June 2015 (UTC)

Ensue your video adapter and northbridge has no damage and sufficient cooling. Are You using the recent tested video drivers to prevent Xserver crashes? Is Memtest without error messages? --Hans Haase (有问题吗) 20:22, 30 June 2015 (UTC)

Postcard printing[edit]

Hi, I'd like to know a few things about printing postcards.

  1. What type of paper is used for printing picture postcards?
  2. What type of printer is used? Please specify some examples of models...

Hope someone one will help me out soon...--Joseph 17:46, 28 June 2015 (UTC)

The US Postal Service has specifications about postcards: http://pe.usps.com/businessmail101/mailcharacteristics/cards.htm — Preceding unsigned comment added by 75.139.70.50 (talk) 19:26, 28 June 2015 (UTC)
I'm getting this service is unavailable error. Meanwhile I'm from India.--Joseph 03:05, 29 June 2015 (UTC)
Postcard size is A6 and probably around 170 gsm --TrogWoolley (talk) 10:25, 29 June 2015 (UTC)
Which is better for it; matte or glossy paper..? Also, type of printers used...?--Joseph 10:39, 29 June 2015 (UTC)
You would want photo quality paper (another option is to run it through a lamination machine after). There are printers specifically designed to print this size, or you can print a full sized sheet and cut it down. The special printer would make sense only if you are printing larger numbers. In any case, I suggest a cheap 4 ink inkjet printer (3 colors plus black) or a color laser printer, if you are willing to spend the money for that. StuRat (talk) 20:17, 29 June 2015 (UTC)
Photo quality paper does have a glossy surface, isn't it.? I don't need that. I want to make postcards that will look like real postcards. Hope you understand what I mean.. --Joseph 02:48, 30 June 2015 (UTC)
You're going to need thicker paper, like card stock. I don't quite follow what you mean about not wanting a glossy surface. Postcards that I've seen all have a glossy surface on the side with the picture. (There are postcards without pictures, but you specifically mentioned "picture postcards" in your Q.) StuRat (talk) 04:11, 30 June 2015 (UTC)
I mean I don't need paper (that attracts our fingerprints and dirt) that is usually used for printing photos. Postcards are made of a different type of paper with the front side smooth and backside rough. I don't know what to call that type of paper. That's what I need.--Joseph 05:03, 30 June 2015 (UTC)
Laser printers use toner. Toner is plastic powder molten on the paper. Ink may be affected when getting wet be resolving in the fluid. Not every color laser printer supports photo quality. --Hans Haase (有问题吗) 20:27, 30 June 2015 (UTC)

June 29[edit]

GET and POST[edit]

   function show(e)
   {
   $.ajax({
       type:"POST",
       url:"select.php",
       data:{action:e},
       success: function(data)
           {
               $("#content").html(data);
           }
       });
   }

I'm calling this function onClick on any button and passing value from there to the function, using this function show() the control goes to another file select.php from where the result come back to the current page, everything is working fine, I want to pass all the values from all the buttons or select options or checkboxes which all are already selected, and remove the variable when any option is deselected, ? how to do this ?? — Preceding unsigned comment added by 106.51.131.180 (talk) 07:58, 29 June 2015 (UTC)

Get the value of each element and create either a GET or POST query. Send that with the AJAX request. It will show up in your PHP script in either $_GET or $_POST, depending on how you sent it. 209.149.113.185 (talk) 12:06, 29 June 2015 (UTC)
I added a title. StuRat (talk) 17:54, 30 June 2015 (UTC)

How to copy guidelines to another document in Photoshop?[edit]

Hi, I need to get the exact guidelines used in a document on another one in Photoshop. How could I do it..?--Joseph 15:28, 29 June 2015 (UTC)

Just to clarify the question, are these "guidelines" just text in one Photoshop file that you want to replicate in another ? If you then modify the original, do you need the "copy" to also automatically update with those changes ? StuRat (talk) 20:12, 29 June 2015 (UTC)
The question does not need clarifying; guides in PhotoShop are lines used to help position objects. This is a rather frequently asked question, but the versions I know about don't provide a direct way of doing it. However, it is possible to find a number of guide-copying scripts that can be downloaded, for example at http://pspanels.com/copy-guides/. Looie496 (talk) 21:59, 29 June 2015 (UTC)
Oh, those type of guide lines. I thought he meant guidelines. StuRat (talk) 22:05, 29 June 2015 (UTC)
Resolved

How to send strings over network using TCP/IP protocol in Python 3.4?[edit]

Hello everyone. How would I send strings between python consoles in python 3.4? I think I would use the TCPServer class in the socketserver module. I am running Python 3.4.3 under windows 7. I basically want to run a function on PC A and have it send an argument to PC B and have the console on PC B display the message that it just received. Thanks for your help in advance, —SGA314 I am not available on weekends (talk) 19:30, 29 June 2015 (UTC)

Edit: I have managed to get a TCP/IP server that allows the client to send a message to the server. However, I can't seem to get the client to send messages after it has connected. Here is my client and server code: Server:

import socket
import threading
import socketserver
ConnectedClients = {}
class ThreadedTCPRequestHandler(socketserver.BaseRequestHandler):
    def handle(self):
        data = str(self.request.recv(1024), 'ascii')
        message = data.split(":")     
        if message[0] == "ConnectClient":
            if not message[1] in ConnectedClients:
                ConnectedClients[message[1]] = self.request.getsockname()
                response = bytes("Added " + str(ConnectedClients[message[1]]) + " To the server.", "ascii")
                self.request.sendall(response)
        else:
            #print(message[0])
            exec(message[0])
            cur_thread = threading.current_thread()
            response = bytes("{}: {}".format(cur_thread.name, "recived " + data), 'ascii')
            self.request.sendall(response)

class ThreadedTCPServer(socketserver.ThreadingMixIn, socketserver.TCPServer):
    pass

if __name__ == "__main__":
    # Port 0 means to select an arbitrary unused port
    HOST, PORT = "localhost", 9999
    
    server = ThreadedTCPServer((HOST, PORT), ThreadedTCPRequestHandler)
    ip, port = server.server_address

    # Start a thread with the server -- that thread will then start one
    # more thread for each request
    server_thread = threading.Thread(target=server.serve_forever)
    # Exit the server thread when the main thread terminates
    server_thread.daemon = True
    server_thread.start()
    print("Server loop running in thread:", server_thread.name)

Client:

import socket
import __main__
def client(message, ip = "localhost", port = 9999):
    if not hasattr(__main__, "Connected"):
        setattr(__main__, "Connected", False)
        
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((ip, port))
    data = bytes("ConnectClient" + ":" + "Client1", "ascii")
    #print(data)
    if __main__.Connected == False:
        sock.sendall(data)
        __main__.Connected = True
        
    sock.shutdown(socket.SHUT_WR)
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.connect((ip, port))
    #response = str(sock.recv(1024), 'ascii')
    #print("Received: {}".format(response))
    try:
        msgdata = bytes(message, 'ascii')
        #print(msgdata)
        sock.sendall(msgdata)
        response = str(sock.recv(1024), 'ascii')
        #print("Received: {}".format(response))
    finally:
        pass
        #sock.close()

SGA314 I am not available on weekends (talk) 20:16, 29 June 2015 (UTC)

What problem are you having? Your client code defines a function and never calls it. If you put if __name__ == "__main__": Sendmsg("hello") at the bottom, it should work.
Note that your server will not necessarily get the whole message, even if it's under 1024 bytes, because it might be sent in pieces and recv will return only the first piece. You need to call recv in a loop until you've gotten the whole message. To prevent the server hanging if the message is less than 1024 bytes, you should either send the actual length first (probably in a fixed-length encoding to avoid a chicken-and-egg problem) or else call sock.shutdown(socket.SHUT_WR) after sock.sendall in the client to tell that server that no more data will arrive. -- BenRG (talk) 05:35, 30 June 2015 (UTC)
This does work but not the way I want it to. Its only a 1 way communication. I can only send messages from the client to the server. But I can't do the reverse. Also when either the client or the server gets a message, I want to do something with it, like execute it using the exec function. But I can't do this because the server is being tied up by polling for request. Now I have tried shutting down the server when it gets a message but that didn't work either. So my problem is this, the setup is only 1 way not 2 way, and the server can't do anything because its tied up from the serve_forever function call. —SGA314 I am not available on weekends (talk) 13:13, 30 June 2015 (UTC)
Edit: I have fixed the problem of the server being tied up by handling request asynchronously. But I still don't know how to send the client messages from the server. And here is another question, How would I get a list of connected clients on the server and use that list to allow clients to send other clients messages through the server? —SGA314 I am not available on weekends (talk) 13:50, 30 June 2015 (UTC)
Edit: I have now fixed the problem of getting a list of connected clients. Now I only have to figure out how to get the server to send messages to clients. Does anyone know how to do this with the code above? —SGA314 I am not available on weekends (talk) 18:29, 30 June 2015 (UTC)

php simplesaml and wamp[edit]

Hi there, I've been trying to install SimpleSaml on wamp:
https://simplesamlphp.org/
But when I try to install it, I get 404 error, about welcome_page.php.
After I checked the web it seems I should have added virtualhost to apache.conf.
Unfortunately, whenever I do it, all of the rest of the files on my server isn't available.
1)Does anyone have a solution to the described problem?
2)Does anyone know a good way to implement Saml into php? — Preceding unsigned comment added by Exx8 (talkcontribs) 21:53, 29 June 2015 (UTC)

Typing on mobile keyboards with finger held down[edit]

I discovered, totally by accident, a feature on my Windows Phone I hadn't encountered before: you can type long words quicker by, instead of tap-tap-tapping on the virtual keyboard, holding down your finger and sliding it around the keyboard from one key to another, then releasing on the final letter. (A trail follows your finger by way of feedback.) The software then guesses what word you were aiming at. It's genuinely been a while since I've had such a "wow, that's actually pretty clever" moment with technology. It makes it much quicker to type long words and it's impressive how it can distinguish the letters you want from the letters you're just sliding over. Plus it makes you feel like a wizard.

What's the official term for this kind of typing? I tried Googling "hold down finger typing Windows Phone" but got nothing - just a couple of tips-and-tricks listicles which didn't mention it. --87.224.68.42 (talk) 08:44, 30 June 2015 (UTC)

There doesn't seem to be an 'official' name for it, but I've heard 'gesture typing' used. The first (?) and best-known gesture keyboard was Swype, so people sometimes use that name to refer to the concept as whole too. —Noiratsi (talk) 08:54, 30 June 2015 (UTC)
I've always heard it referred to as "swiping" as opposed to "gestures". The difference is very trivial. A gesture is solely about the shape you draw (or the motion of your hand if it is a camera-based gesture). It doesn't matter where you draw it or how big/small it is. For example, if I sweep from right to left and then wiggle up/down real fast, that tells my browser to go back (but, it is easier to hit the back button). With swiping, you have to get near the keys you are using. Otherwise, the shape you draw will over the wrong keys and produce the wrong word. Of course, you don't have to be perfect. Getting near the keys is usually enough to match the location-based gesture you want. In my opinion, I would place swiping as a subset of gestures. More specifically, I would place it as gestures constrained to a position on the screen. 209.149.113.185 (talk) 15:36, 30 June 2015 (UTC)

Inno Setup help[edit]

(See also DLL hell for the general subject). I have to put together an Inno Setup script, which includes one problem DLL. What I need to do is:

  1. If the DLL isn't installed on the system, install version 3.0.5 (the latest).
  2. If version 1.x or 3.0.0 to 3.0.4 is installed on the system, install version 3.0.5.
  3. (And this is the tricky bit) If version 2.x is installed on the system, don't replace it.
  4. If version 3.0.5 or later is installed, prompt the user for overwriting (this is done with the promptifolder flag).

Is this possible, or will I have to put together a set of manual instructions? Tevildo (talk) 18:15, 30 June 2015 (UTC)

Web page gotchas[edit]

I suspect that some web pages intentionally do the following:

1) Place an innocent button where it renders immediately, say "Like this".

2) Place an evil button such that it will render in the same spot, a second later. For example, "Donate all the funds in my account to ...".

3) They then get people who try to click on #1 but accidentally hit #2.

Has anyone admitted to designing web pages like this intentionally ? StuRat (talk) 19:13, 30 June 2015 (UTC)

Wikipedia regularly has a banner that loads with a slight delay so when you try to click on the search button at the top of the page, it quickly places the DONATE button where the search box used to be. Is it intentional? 209.149.113.185 (talk) 19:30, 30 June 2015 (UTC)
No. Web browsers often don't know how large an element is going to be until they have downloaded it. It's very common to see pages rearrange themselves as the elements are filled in. This is a result of browsers being programmed to show you something as soon as possible, rather than leaving the page blank until all its contents have been downloaded. Looie496 (talk) 19:58, 30 June 2015 (UTC)