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November 2

JPEG compression question

When I save a JPEG in Photoshop Elements, it asks me for the amount of compression. There is a selection or quality (up to "maximum") and a number. You can change either one. If you select Maximum, the number defaults to 10, but you can change the number up to 12. Does turning it to 12 get more quality than 10? Bubba73 ^{You talkin' to me?} 02:15, 2 November 2015 (UTC)

I don't know the answer - but you can find out. Save an image at 10 and then save the same image under a different name at 12. Look at the size of the files - if the '12' file is larger than the '10' file, then it's almost certain that the 12 file has better quality...if the files are the same size - then almost certainly they are identical. SteveBaker (talk) 04:46, 2 November 2015 (UTC)

The "12" files are larger. Bubba73 ^{You talkin' to me?} 04:48, 2 November 2015 (UTC)

Here's a nice analysis of "quality" setting for jpegs. Here's [1] another that focuses on the blocking and how it interacts with the "quality". These approaches are rather empirical, but you can also look into the technical specs to determine what's going on from first principles [2]. In short, 10 is a default near-max, because in general increasing the value to 12 won't help much, but in some certain cases it may. SemanticMantis (talk) 15:58, 2 November 2015 (UTC)

Thanks, this answers my question:

“0-100” is really “0-12” — Lightroom maps the 101 points in its 0-100 quality scale to only 13 different quality outputs. Setting the Lightroom quality to 70, for example, results in the exact same output as setting it to 76, or anything in between. 7 is the same as zero, and 93 is the same as 100. The full mappings are shown in the examples below.

Those familiar with Photoshop will recognize 13 as the number of quality settings in Photoshop's Save-as-JPEG option (with 0 being “Low quality”, up through 12 being “Maximum Quality”). I haven't tested whether these are indeed the same except for the numeric scale presented to the user, but I suspect they are.

But I still wonder why if you select "maximum quality", it defaults to 10 instead of 12. Bubba73 ^{You talkin' to me?} 16:04, 2 November 2015 (UTC)

Resolved

Syntax for Regular Expressions doesn't carry over to CFG's

Why does this Article on Syntax Analysis(P.28) says that "Syntax for Regular expression doesn't carry over to Context-free grammar?I have this doubt because even though they say "we can't use * or | in Context Free Grammar" they have used it as shown in the article.Does this mean we can use it in Context Free Grammar?JUSTIN JOHNS (talk) 08:44, 2 November 2015 (UTC)

Well, regular expressions and formal grammars are two different formalisms. A frequent convention is to use the vertical bar | in grammars as a short-hand for alternative productions with the same left hand side. This is similar to the use of the vertical bar is some versions of regular expressions to denote alternatives. The author of the Stanford slides is trying to make sure that the students understand that you cannot use arbitrary regular expressions as right hand sides of grammars (which would result in an effectively infinite set of productions, and really mess parsing theory up). That's why he is stressing the point in the slides. --Stephan Schulz (talk) 11:58, 2 November 2015 (UTC)

I don't think it would mess anything up. There's no theoretical reason why the CFG notation forces you to name every node and the RE notation doesn't. "A → B (C | D)" would unambiguously have the same meaning as "A → B A'; A' → C | D" where A' is a fresh name. "A → B*" could mean "A → AB | ε" or "A → BA | ε", but the only difference between those is the parse tree, and there's no fundamental reason why we care about parse trees for CFGs and not for REs. -- BenRG (talk) 17:25, 2 November 2015 (UTC)

You get into trouble when you allow the Kleene star. Without the Kleene, the language described by the RE is finite, and you can always expand the rules. But if you allow the Kleene star, that expansion becomes infinite. In an formal grammar, only a finite set of productions is allowed. But what is more, typically nothing but | and maybe implicit concatenation is allowed. A confounding factor is that one example in the slides it uses "*" as a terminal symbol, not an operator. --Stephan Schulz (talk) 18:11, 2 November 2015 (UTC)

Yeah you're right that's really confounding.Thanks for clearing my doubt.I've mistaken the "*" as an operator rather than a terminal symbol which the author of slides actually meant to be.Also can we use parenthesis in formal grammars?JUSTIN JOHNS (talk) 06:41, 3 November 2015 (UTC)

A Ben has pointed out above, you probably could, but I've never seen it done in any texts or papers. Since parenthesised expressions are one prime example of a language that context-free grammars can describe and that REs cannot, you'll see '(' and ')" rather often as terminals. Again in the Stanford slides, the author explicitly excludes them: "Cannot use *, |, or parentheses." (page 24ff), just after he introduced "|" in a similar but different role (abbreviating sets of rules with the same LHS into one rule). --Stephan Schulz (talk) 08:22, 3 November 2015 (UTC)

Yeah that's right.It might be for precedence.JUSTIN JOHNS (talk) 08:50, 4 November 2015 (UTC)

How do you get onto the internet (world wide web) of a foreign country?

Let's say that I wanted to get onto the internet (world wide web) of a foreign country. How do I do that? Does the computer somehow "read" my IP Address and "know" that I am in the USA? And therefore it connects me to only USA websites? Or is something else going on? For example, I have typed in a lot of Spanish words in the Google search, thinking that maybe that will take me to some Spanish country's websites. But, it merely took me to the USA websites, translated into Spanish language. So, hypothetically, let's say that I want a search term like "most popular TV shows" (or whatever). But I want the results from, say, the websites of France. How would I get that? If I type in "most popular TV shows", that will take me to USA sites. If I type in "most popular TV shows, French or France", that still doesn't help. What does one need to do? Thanks! — Preceding unsigned comment added by 2602:252:D13:6D70:F186:6FAE:7FE0:7883 (talk) 09:21, 2 November 2015 (UTC)

If you already know what you want to see, just type its addressinto the browsers address bar. If you are looking things up, consider using a search engine based in the country of interest. As I check, I just entered www.google.fr into my address bar and TV ce soir into the search box and I got lots of French sites. -- SGBailey (talk) 09:39, 2 November 2015 (UTC)

You can limit your Google search to Spanish websites by adding the site:.es search operator to the search term. Rojomoke (talk)

I'm pretty sure you can tell google to give you results in a language other than the one it's guessed is yours. —Steve Summit (talk) 11:33, 2 November 2015 (UTC)

@SGBailey, Scs, and Rojomoke: "google.com/ncr" takes to main google site without region redirect. use site:.fr/.se/.de/.countrycode tld to search country-specificMahfuzur rahman shourov (talk) 15:47, 2 November 2015 (UTC)

The Internet is one global network. For instance, here's the website portal of the French government. This is the same website you would get if you were in France. But, you were on the right track. What is happening in your scenario is Google is guessing you are in the U.S., and deciding to show you only English-language results. They are doing this based on your IP address and most likely some other factors. For instance, Web browsers usually send HTTP headers that include a list of requested languages for content. And, if you've used Google before, and your browser keeps cookies, Google tracks your searches to build a profile of you. Based on this, Google shows you the results it thinks you'll be most interested in. Remember, Google is a for-profit business whose goal is to show you ads. They want you to keep using their search engine so you will see their ads, so Google has invested a ton of resources in trying to predict what you're most interested in. --71.119.131.184 (talk) 22:02, 2 November 2015 (UTC)

So where do I find the various codes? Someone above said that "es" was Spanish. Another person above said that "fr" is France. Where do I find those codes? Thanks. 2602:252:D13:6D70:D4BE:FEEC:EC9C:DA2 (talk) 04:38, 3 November 2015 (UTC)

Please see List of Internet top-level domains, specifically the section § Country code top-level domains. -- ToE 05:02, 3 November 2015 (UTC)

It's still not working. I am not exactly sure what I am supposed to be typing in and where? So, say I want to search a topic like "gardening", and I want the French websites for that topic. What do I type exactly? And where? Do I have to go to Google for France (google.com.fr)? Or do I just type the search words "gardening" with the additional "site:.fr"? I am confused. What should I be doing exactly? Thanks. — Preceding unsigned comment added by 2602:252:D13:6D70:186C:D475:39EF:E0EC (talk) 19:00, 3 November 2015 (UTC)

It looks like you can restrict your search to a certain language on the "Advanced Search" page.

Now, google likes to keep the Advanced Search page pretty well hidden -- indeed I thought they'd gotten rid of it a while ago -- but just now I discovered it hiding on the Settings menu in the lower right-hand corner. —Steve Summit (talk) 21:29, 3 November 2015 (UTC)

But also, typing gardening site:.fr works. Note that that will find pages on sites registered with a .fr country top level domain. That does not guarantee French language, and it also does not guarantee that the server is physically in France. Indeed, if you search for an English word, you will still get a lot of English language pages. But try croissant site:.fr after you have selected francais as one of your languages under Settings->Languages->Search Results. Also keep in mind that Google is not the internet, but only a convenient way to find certain pages in the World Wide Web, which runs on top of the internet. You can use the Web without Google (try DuckDuckGo or Bing). --Stephan Schulz (talk) 22:22, 3 November 2015 (UTC)

Thanks. — Preceding unsigned comment added by 2602:252:D13:6D70:2133:96D1:E52:1192 (talk) 19:52, 7 November 2015 (UTC)

Inexplicable DHCP activity

I noticed some strange DHCP activity in my router's "security log":
11/01/2015 23:08:53 DHCP Client: [WAN]Receive Ack from 172.19.57.129,Lease time=86400
11/01/2015 23:08:53 DHCP Client: [WAN]Send Request, Request IP=68.97.47.54 <-- (my WAN IP)
11/01/2015 23:08:53 DHCP Client: [WAN]Receive Offer from 172.19.57.129
(The log entries are in reverse chronological sequence; read bottom up)
These days, I tend to get a little paranoid when I see unexplained activity in my system. When I tried to geolocate 172.19.57.129, it said it's a private IP address, which, according to this page, means an address on my local network. If that's true, it's the first such address I've seen that wasn't in the range 192.168.2.x. And I don't know how to interpret this since the log entries say "WAN". I need to know what this might be, and if I should be concerned about it. 68.97.47.54 (talk) 09:22, 2 November 2015 (UTC)

The mystery IP is your internet provider's DHCP server. Essentially, your computer is actually a member of 3 networks - your home network (handled by your router, using the 192.168.2.X IP range), the Internet (using the whole range of public IPs), and your ISP's network (using the 172.16.0.0/12 block). If everything is going fine, you barely see the ISP's network, but for your computer to interact with the Internet, it needs to get a global IP address. The global IP is given out by the DHCP server of the ISP's network, which is what you're seeing here. A rough translation of the conversation would be:

(ISP DHCP server): "Hey, want an IP address so you can keep using the Internet?"

(Your router): "Sure, I'd like the address 68.97.47.54 if possible"

(ISP DHCP server): "OK, you're now registered with that address. This will last for 86400s, and once that expires we'll do this again."

MChesterMC (talk) 10:42, 2 November 2015 (UTC)

Makes sense, and thanks for the English translation. 68.97.47.54 (talk) 04:53, 3 November 2015 (UTC)

How to stop disable and uninstall the IIS (Internet information service) in Windows 10 home edition?

My instructions where to go to MSconfig via the Search\Run box, there to "Services" and then disable it, but, unfortunately, I didn't find there such a service "IIS" or "Internet information service"; What is the right way to finally remove it in WIN10 so I could finally using port80 and not alternative ports for WAMP? Thanks. Ben-Yeudith (talk) 13:00, 2 November 2015 (UTC)

I'm fairly sure that this is under the "Change or Remove Windows Features" dialog in the Control Panel. I'm not at a Win10 computer right now so I can't double-check it for you, but searching the Start Menu for "windows features" brings it up in Windows 7. In that window there'll be a box for IIS, uncheck it and IIS should be removed. 67.133.155.66 (talk) 13:45, 2 November 2015 (UTC)

Thanks, it was under "Control panel" > "Programs and features" > "Turn windows features on or off" (I needed to use the search box a bit to find that). Ben-Yeudith (talk) 17:07, 2 November 2015 (UTC)

difference

W8 v W7 64bit.? Also do you need 64bit ram?31.55.64.143 (talk) 20:47, 2 November 2015 (UTC)

There are a few differences between 32-bit and 64-bit operating systems (some are listed at 64-bit computing#64-bit applications). You don't need special RAM to run a 64-bit version of Windows, but you will need a 64-bit processor. clpo13_(talk) 22:05, 2 November 2015 (UTC)

(edit conflict) Hey look, we have articles on both Windows 7 and Windows 8. There is no such thing as "64-bit RAM". You do need a 64-bit processor to run a 64-bit version of Windows, but all x86 processors released in the last decade have 64-bit support, so you don't need to think about it unless you're planning to use some pretty old hardware. --71.119.131.184 (talk) 22:12, 2 November 2015 (UTC)

That isn't necessarily true of low-end hardware. The Intel Atom Z2580, released in Q2 of 2013, is 32-bit only. I don't know if anyone runs Windows on it, though. -- BenRG (talk) 06:44, 3 November 2015 (UTC)

Oh hey, I stand corrected. Intel Atom says some but not all support 64-bit, and you can run Windows on the Atom. But yeah, I think few individuals are buying bare Atom systems and installing Windows on them. --71.119.131.184 (talk) 06:50, 3 November 2015 (UTC)

I think there were definitely people running Windows on the Atom systems on Netbooks and Nettops. They only had a niche market but were there. Besides CPU support issues, there were also driver issues e.g. Intel Atom (CPU)#Intel 64 software support [3]. Nowadays of course there are the HDMI dongle sized mini computers and people also try WIndows on these. Intel's support for Windows 64 bit on their lowed end systems has always been a bit weird, their Bay Trail CPUs aimed at the tablet market lacked drivers for always on standby in the early days meaning all of these were 32 bit Windows, and generally 2GB although I think LPDDR3 RAM chip sizes in the early days made 4GB difficult anyway. (You could of course run 4GB on Windows 32 bit, but the limitations meant I don't think this was likely with the tablets. Not that the Bay Trail WIndows tablets were ever that popular, but they were at least more popular than the ARM/Windows RT ones) Nil Einne (talk) 07:19, 3 November 2015 (UTC)

I know about the existence of Atom netbooks. I worded my statement very carefully: "individuals buying bare Atom systems", i.e., bare metal. It sounds like the original poster is building their own PC and installing Windows on it, which is why they're asking about required hardware. If they're buying a finished system, they don't need to care about RAM or CPU support for the OS, as that's the job of the system manufacturer. --71.119.131.184 (talk) 19:29, 4 November 2015 (UTC)

Right but although my comment was in reply to you, it also mentioned the general issues with Atom systems and 64 bit Windows, and these problems apply to both netbooks (which you didn't mention, but which are relevant to the OP and which evidentally do use the D2550 mentioned by BenRG (http://www.aliexpress .com/item/14-Netbook-PC-Ultra-Thin-Intel-Atom-D2500-D2550-Dual-Core-1-86Ghz-4GB-RAM-500GB/1410107355.html) and to any other system with an Atom.

I also mentioned Nettops besides Netbooks. Nettops may be finished systems, or they may be bare metal or they may be even less (e.g. just a mobo with CPU and possibly RAM). People have bought them for a variety of reasons, general systems, downloads computers (i.e. for most people torrent boxes), probably even some seeding boxes, car computers and a bunch of other uses I can't think of offhand. Probably some even used them for media computers, even though they often weren't that good for it. Only the car one and perhaps the seed box is most likely not going to be using Windows (or if it did, probably one of the embedded versions). People may suggest another OS for download computers, but most people seem to choose Windows, because it's what they're familiar with and what the programs they use work on.

Also, your later statement isn't true. In fact it isn't that uncommon for a system including laptops sold to the everday consumer for everyday use in some parts of the developing world to come with no OS or more likely FreeDOS to reduce cost. Particularly cheap systems which in the developing world would generally have ultra low end hardware (i.e. Atoms). Although far from exclusively, e.g. here is a 4th gen Core i3 with FreeDOS [4] and here is a 5th gen i.e. Broadwell Core i7 [5] (I think the 5500U [6]) . It shouldn't surprise anyone with a bit of knowledge to realise no one is going to be using FreeDOS on these long term. Sometimes Linux may be installed on these systems (and very occasionally something else like some BSD variant or OS X), but I'm pretty sure more commonly Windows without a proper licence. Also, if your system came with 32 bit Windows (perhaps Windows Vista or even XP), and you want to upgrade, you probably want to consider what version of Windows to install, like the OP is doing.

Note that your specific earliest comment (to which I was also partly replying to as part of the thread) was "but all x86 processors released in the last decade have 64-bit support, so you don't need to think about it unless you're planning to use some pretty old hardware", which seemed to imply both old and new systems. "New" is also relative here. If someone buys a refurbished system, that may be new to them, but if it's 4 years old, it seems it could have a CPU which will have problems with 64 bit Windows. The OP is evidentally from the UK (and possibly a troll, but I digress), so probably this isn't that likely, since you can easily get a Core 2 Duo for I guess GBP40 or less (based on prices here in NZ). But unless the OP mentions where they live, it's not always necessary to check such info and resonable to give general answers particularly in a case like this (as opposed to something which is highly specific to the geographical location). And such systems often don't come with an OS, having been wiped.

In other words, the assumption that someone who buys or bought a system doesn't need to consider whether their system supports 64 bit Windows is flawed.

Note that the statement "do you need 64bit ram", doesn't have to mean "what RAM should I buy" but could easily mean "do I have to worry about whether my RAM will work with 64 bit Windows"? And in fact, given the OP's limited knowledge, there's a fair chance they weren't building their own system, so may very well be doing one of the others. I.E. Upgrading the OS on an existing system or installing Windows on a new or refurbished system they just acquired. Given the additional details of the UK, it's probable this isn't an Atom, but it can't be ruled out entirely, particularly in the first case and in any case no one mentioned the OP being in the UK until I did.

My ultimate point is that just because it's Atom, doesn't mean no one was installing Windows on it, it's likely a fair few people were (whether or not it was a sensible choice).

Nil Einne (talk) 14:51, 5 November 2015 (UTC)

xargs file-per-line option?

When the xargs program reads filenames from its standard input, by default it parses each whitespace-separated "word" as a distinct filename. It also has an option -0 which causes it to use null bytes on its input as filename separators. I thought there was another option to use newline (\n) as the separator, but lately I haven't been able to find it. (It would be a really nice option, and IMO it should be the default, but that's a rant for another day.) —Steve Summit (talk) 23:26, 2 November 2015 (UTC)

Answering my own question, you can use -d '\n', but unfortunately it's not available in all versions. —Steve Summit (talk) 23:27, 2 November 2015 (UTC)

Unix pathnames can contain newlines (or any character except NUL, hence the motivation for the addition of -0 in some xargs implementations), so that doesn't make it any safer for handling pathnames. If you can't use xargs -0 with null-delimited input, use something else, like find(1), shell globs and loops, or your favorite scripting language. Here is a good starting point if you need help. --71.119.131.184 (talk) 06:45, 3 November 2015 (UTC)

You could of course write tr '\n' '\0' | xargs -0, but I agree with 71.119.131.184 that it's risky to use anything except \0. -- BenRG (talk) 06:51, 3 November 2015 (UTC)

Thanks, both. I do know about newlines in filenames (in fact ~/tmp currently contains two such files, for use in testing the script I'm writing). What I'm angling for is a compromise: xargs in its default mode is useless (it can't even handle space characters in filenames, which are ridiculously common today), while xargs -0 is nearly impossible to use in a general way, because "list of filenames separated by null characters" is such an unusual datatype, supported in an ad-hoc way by only a tiny handful of programs. Instead, I'm going to use "list of filenames, exactly one per line", and I'm willing to discard (i.e. not be able to handle) filenames containing newlines.

tr '\n' '\0' | xargs -0 is a nice idea, and I wish I'd thought of it myself. Thank you. (One must beware, though, that it won't work with non-GNU versions of tr, which maddeningly cannot handle, and IIRC Posix does not even require them to handle, null characters.) —Steve Summit (talk) 14:33, 5 November 2015 (UTC)

This is still insecure if you're getting the pathnames from the filesystem. You can't just use find -exec or shell globs? Both are available on every POSIX system. --71.119.131.184 (talk) 01:21, 6 November 2015 (UTC)

Uh oh, it looks like the glove has been thrown, and there's a suggestion that I have a complacent attitude towards security. So I guess I'd better defend my honor.

Several points:

• I did not ask, "How can I list and process arbitrary filenames securely?" The question was merely, "Does xargs have a line-at-a-time option?", and that question has been answered.
• There seems to be an assumption that I'm writing some variation on

find -print | xargs cmd

(which would indeed be insecure), and it's asked why I can't write

find -print0 | xargs -0 cmd

or

find -exec cmd \;

instead. But neither of those will work for me, because what I'm actually doing is along the lines of

find | a bunch more processing | xargs cmd

and trying to pass null-separated filename lists around during all of that "more processing" is, well, out of the question.

• The script in question involves selecting files for backup. So the worst that can happen is that a file whose name contains a newline doesn't get backed up, and/or that some other file gets backed up twice.
• The backups are of my personal computer that no one else ever uses. And I never create files with newlines in their names. (Well, hardly ever; as I mentioned I've just recently created a few for testing, as part of this exercise.)
• This is where I say something like "So I don't care about security", and you come back with "But you must care about security! It's because so many people say 'I don't care about security' that there are so many badly insecure systems in the world!". And you'd be right, except that
• I simplified the pipeline up in step two. I am, in fact, using -print0 up front:

find -print0 | a bunch more processing | xargs -whateverittakestodonewlineseparation cmd

, and the first steps in "a bunch more processing" are to (a) filter out (and noisily warn about) any filenames containing \n, and (b) convert the rest from separated-by-\0 to separated-by-\n so that all the rest of the processing can use the more convenient (much more convenient!) representation.

So can we finish up with the lectures about xargs and newline security now? :-) —Steve Summit (talk) 15:21, 6 November 2015 (UTC)

November 4

Chrome problems?

Are there problems existing now with Chrome that would make it unable to access some ordinary web sites? I have six sites up right now, and one tab is stalled. I can access this site from Firefox and IE. Halcatalyst (talk) 03:16, 4 November 2015 (UTC)

Here is a current list of bugs/issues [7], here's how to report a problem [8], here's a little more about bug tracking and reporting for the project [9]. SemanticMantis (talk) 05:24, 4 November 2015 (UTC)

Simplification of CFG

Can we simplify the grammer given below(Grammar 1) into the one below(Grammar) that.The first grammar is in the Article on Synatax Analysis(P.129).

Grammar 1

R → S | R “|” S

S → T | ST

T → U | T*

U→a|b|...

U → “ε”

U → (R)

Grammar 2

R → S | R "|" S | SR

S → S* | "ε" | (R) | R |a|b|.... JUSTIN JOHNS (talk) 09:46, 4 November 2015 (UTC)

I think they generate the same language, but Grammar 1 is unambiguous and Grammar 2 isn't, so it may not be a useful simplification in context. Note that since Grammar 2 has R → S and S → R productions, you can simplify it further by merging R and S, and that gets you (back to) the grammar of page 120. -- BenRG (talk) 17:19, 4 November 2015 (UTC)

Could you explain how can we merge R and S from Grammar 2 to get back the grammar of page 120.JUSTIN JOHNS (talk) 06:25, 6 November 2015 (UTC)

Is Hidden Left Factors an issue in Parsing?

It's true that left factoring solves the issue when common prefixes on the right side of the production.I would like to whether hidden left factors creates an issue in parsing as given in Formal Grammars(P.9) since at the first parse the parser might be confused to apply which production when common prefixes appear on the right side of production.While if there is hidden left factors does it create any issue in first parse when common prefixes doesn't appear on the right side of productions?JUSTIN JOHNS (talk) 10:04, 4 November 2015 (UTC)

It creates problems for parsers because the sentence to be parsed doesn't contain any nonterminals. If you have B → abB | daA | Af (the example from that handout) and the sentence to be parsed as a B starts with da, the parser can't choose between B → daA and B → Af unless it knows that A can't produce any sentences starting with da. Looking for A in the sentence won't help because A doesn't appear in sentences. -- BenRG (talk) 17:38, 4 November 2015 (UTC)

Could you make clear what you meant by "unless it knows that A can't produce any sentences starting with da".JUSTIN JOHNS (talk) 06:30, 6 November 2015 (UTC)

SATA M.2 vs PCIe M.2

If I buy a laptop with a SATA M.2 SSD, can it be upgraded to a PCIe M.2 SSD later? Or will I be restricted to SATA M.2 SSDs? Thanks --RM — Preceding unsigned comment added by 203.199.213.3 (talk) 18:27, 4 November 2015 (UTC)

It looks like it, though you specifically need an M.2 SSD. You can't buy just any PCIe SSD, as the majority are for desktops and use the larger desktop motherboard PCIe slots. --71.119.131.184 (talk) 21:11, 4 November 2015 (UTC)

Resonance and Reactive Power with Square Wave AC

If a capacitor or an Inductor is powered with a square wave ac supply will they be able to exhibit properties such as resonance and draw reactive power like they will do with a sine wave supply?--Adenola87 (talk) 22:33, 4 November 2015 (UTC)

Yes. Passive devices like capacitors and inductors behave mostly linearly - so this means you can use linear superposition to analyze the square wave as the sum of many separate sine waves with separate frequencies and amplitudes. For practical purposes, the power from each frequency does not interact with the power from any other frequency (because the components are well-modeled as "well-behaved" linear systems). Nimur (talk) 22:42, 4 November 2015 (UTC)

MozyHome backup/restore

I've used the MozyHome backup/restore system for some time. Recently I restored, but some files wee missing. After several rounds on chat support, I am told that Mozy does not necessarily back up files/folders that were added after the initial backup took place. How can this be? Is this standard practice for this type of service? The agents I talked to all seemed to presume that I had (or should have) configured all sorts of settings, and I don't even remember ever having had the opportunity to do so. Halcatalyst (talk) 22:45, 4 November 2015 (UTC)

Our article does appear to confirm that after the first backup Mozy by default only takes incremental backups of files that existed at the time of the first backup. That does seem to me to be unexpected behavior that's likely to bite users. I can't give you any specific data on how common this behavior is. Personally I'm a bit of control freak anyway, and stories like this just make me even more determined to avoid commercial "backup solutions". rsync for the win! --71.119.131.184 (talk) 01:30, 6 November 2015 (UTC)

The files it skipped for me seem to be random, so I just don't get it.

rsync sounds good, but I'm far too non-technical for that!

What about backing up into a cloud? What are the pros/cons of that? Halcatalyst (talk) 02:08, 6 November 2015 (UTC)

The saying I am fond of is that "cloud" is just another word for "someone else's computer". In general having remote backups is a good thing. Ideally you want both local and remote backups. But you have to take into account the reliability of the hosting party. If they disappear one day, there go the backups you've stored there. And if your data is not encrypted securely, the other party has access to it, as does anyone who might gain unauthorized access. Again, none of this makes remote backups a bad thing. They're just factors to take into account. --71.119.131.184 (talk) 06:26, 7 November 2015 (UTC)

Here's the full story. When you sign up with Mozy, you specify the types of files you want backed up: document, pictures, videos, etc. The filetypes (what does "filetype" mean to the average user?) underlying these categories, and no other, will then be backed up, unless you take positive action to add others. I certainly didn't understand that when I started with them in 2010, and it only became clear the other day when an agent explained it to me.

However, there is a happy ending: the Mozy manager telephoned me and we had a long talk. In the end, he offered me generous support going forward, including direct access to his technicians. And Best Buy was able to complete a file transfer from my dead computer's hard disk. It took 11 hours, because of power problems with the HD. But I have all my files back!

Thank you all for your help. Halcatalyst (talk) 23:28, 7 November 2015 (UTC)

Mother board reliability

How reliable are todays desktop motherboards? When they fail, what is it that most often fails?109.144.180.19 (talk) 23:34, 4 November 2015 (UTC)

For me , motherboard failure is very rare, except Capacitor plague got me once. GangofOne (talk)

I've also found them to be robust. I've had network ports blown during lightning strikes back in the ADSL days, but nothing more serious. I've found case switches to be prone to power surges, and most often it's the PSU or power supply which dies after a power surge. Sandman1142 (talk) 12:21, 5 November 2015 (UTC)

It is very rare that I've seen a motherboard failure that wasn't user error or a bad power supply, which I don't consider part of the motherboard. 209.149.114.132 (talk) 13:13, 5 November 2015 (UTC)

As GangofOne sort of hinted at, on the past capacitor plague was resonably common cause of failure for motherboards. This is a lot less commom now, still I wouldn't say it never happens and (discounting user error) is probably the most common cause of failure (that or the VRMs). I've also had intermited problems which are probably because of the board (without apparent capacitor plague I mean), such as cold boot issues. Nil Einne (talk) 13:52, 5 November 2015 (UTC)

Well first off, I had aproblem with not being able to get a new printer to work via usb. Sometimes the compurter would recognise the printer and sometimes it wouldnt. At no time could I get the printer to print from the comuter. Some fiddling with the usb connectios would sometimes change the computers ability to recognise the pri ter. Then I looked at the usb main ports and found them filled with dust as they are near to the main fan which was also clogged with dust. I cleaned both fan and ports and retried printer again without sucess. Now howevdr the computer refused to recognise the printer at all . ? After the umpteenth reboot the computer refused to start and I got the bsod telling me to remove new hardware and drivers etc. Removed alll new hardware. Still wont bbot.31.55.64.30 (talk) 23:12, 6 November 2015 (UTC)

Thee are motherboard manufacturers `who do the kind of things things that we electronics engineers normally do when we are designing for high reliability.

For example, the Gigabyte ultra-durable line ( http://www.gigabyte.com/microsite/98/html/technology-guide-ultra-durable-f.htm ) has a lot of the design features that I use when designing something that will go on a commercial aircraft. --Guy Macon (talk) 17:38, 5 November 2015 (UTC)

Yeah but is it possible that a transient or semipermanent motherboard fault could trash files on the hard disk?86.187.188.120 (talk) 00:31, 6 November 2015 (UTC)

It's certainly possible, since the motherboard is how the computer components talk to each other. But, the most common hardware-related cause of data loss is hard drive failure. Is there a specific issue you're having? If so, can you give us the exact details? --71.119.131.184 (talk) 01:35, 6 November 2015 (UTC)

November 5

grep for shell glob patterns?

So we've got grep, egrep, and fgrep that accept different variations on regular expressions, and in fact these days they're all the same program, with (if you wish) -E, -F, and -G options to select the regexp style.

And as we all know, a regular expression is not the same thing as a shell glob pattern.

So my question is, has anyone ever come across a shell-callable grep variant that matches glob patterns? Or am I going to have to write my own? (For pedantry's sake I may have to call it ggpp.) —Steve Summit (talk) 02:13, 5 November 2015 (UTC)

I suppose it's possible someone has written one, but it's not widely distributed, probably because if you have a shell, you can just do the searching with the shell, using a while-read loop. --71.119.131.184 (talk) 03:00, 5 November 2015 (UTC)

Well, the point is that the shell generally wants to expand glob patterns to lists of filenames, and that doesn't help if you want to apply a glob pattern to something else. So the issue mostly isn't how you iterate, but how you test. However, there is at least one exception to that "generally", and that is case statements. So consider this code:

while read line

do

case "$line" in

$pat) printf "%s\n" "$line";;

esac

done

Unfortunately, this fails if the input lines start or end with whitespace, because read strips it, at least in both the sh and bash implementations I have access to. I guess you could do this:

while read line

do

case "/$line/" in # Note: / is just an arbitrary character here, not a regexp delimiter

/$pat/) printf "%s\n" "$line";;

esac

done

But maybe there is some newfangled easier way that I don't know. Hey, I hadn't even heard of printf as a shell command until I started writing this. --70.49.170.168 (talk) 07:36, 5 November 2015 (UTC)

Oops, never mind that last part; it attempts to apply protection too late, after read has already stripped the whitespace. --70.49.170.168 (talk) 07:38, 5 November 2015 (UTC)

Use while IFS= read -r line. This stops read from modifying the input. You should always use read like this for reading in whole lines, unless you know you want other behavior. See my link to the BashFAQ above for more details. You may also want to look at the bash manual and the POSIX standard for more information on how read works. (read is a shell builtin, so man read won't give you anything, which is something that often trips people up.) --71.119.131.184 (talk) 08:22, 5 November 2015 (UTC)

Thanks for the IFS= trick. I've used IFS to modify the behavior of read before, but never thought of setting it to a null string. --70.49.170.168 (talk) 21:18, 5 November 2015 (UTC)

After sorting out the whitespace, you can use just [[ $line == $pat ]] in bash. --Tardis (talk) 13:43, 5 November 2015 (UTC)

You can? <tries it> I'm stunned. Whouda thunk? I won't be using that, but thanks for providing a new data point for the old adage that you learn something new every day. —Steve Summit (talk) 15:14, 5 November 2015 (UTC)

Also, to be pedantic, grep -F/fgrep doesn't use regexes at all. It searches for "fixed" strings, hence the name. As our grep article kind of tells you, it dates back to V7 Unix, when computers were much much slower. Having a program that didn't do any regex interpretation made sense, for when you knew you just wanted to do string searches. --71.119.131.184 (talk) 03:12, 5 November 2015 (UTC)

Thanks, guys. In this case the patterns won't be known 'til run time (so the case trick won't work without a whole lot of hacking), and the script is bordering on the slow side already, employing lots of shelly machinations for each directory it processes, so once I'm down to iterating over the filenames in a directory, I'd like to do so with a one-pass external program, not more shell loops.

I do have my own glob-matching code lying around somewhere (and even my own version of grep, for that matter), so integrating the two won't be much trouble. (Heck, I might even integrate into GNU grep, and contribute my mods back to the FSF.)

To be even more pedantic, even back in the days when Unix was young and computers were "slow", the word on the street was that egrep was faster than fgrep. fgrep is useful when I do want a fixed-string match with no special characters interpreted, but if I care about speed I always use egrep. —Steve Summit (talk) 14:51, 5 November 2015 (UTC)

It's an interpreter! The case trick does not require the pattern to be known in advance. Note that I wrote $pat in there. And it works in sh, so you don't need to bring bash into it. --70.49.170.168 (talk) 00:52, 6 November 2015 (UTC)

ixquick and startpage.com, business model?

ixquick and startpage.com offer websearch for free, by using a proxy that anonymizes Google results (startpage.com) or by aggregating the results from several search engines (ixquick). They have been awarded for not tracking their users. And there are no ads. So how do they earn money? --NorwegianBlue ^talk 08:11, 5 November 2015 (UTC)

This company is privately owned - and they even proudly acknowledge that they "do not report financial information." They have no legal obligation to explain how they are profitable; they probably have no legal liability if they lie about being profitable. (It's the same reason that you don't have to publish your paycheck stubs on your Wikipedia user-page - because you don't have to!). The company webpage claims that they are profitable and that some of their revenue comes from sponsored search results. Along the same lines, you could claim that you're making tons of money, and nobody could prove it one way or another using public information. You're allowed to tell your friends that you're a super-rich, super-profitable millionaire, in a feeble and superficial effort to impress them with material wealth - and this is perfectly fine and legal, whether it is true or false - unless you're lying to them so you can raise regulated securities. Privately-owned corporations generally have the very same freedom: they don't have to "post their pay stubs" to back up their statements. For all we know, every word of it is true!

You could mail the Ixquick press contacts to see if they have any statement or investor-information that is not hosted on their website.

Nimur (talk) 09:23, 5 November 2015 (UTC)

Thanks! NorwegianBlue ^talk 15:44, 5 November 2015 (UTC)

They do show ads. Try searching for something buyable, like "toaster". This page says "We earn 99 procent [sic] of the money from the ads we show on our results pages." Since they're just an anonymizing proxy for other companies' services, their operating costs are probably low, so there's no reason they couldn't be profitable. -- BenRG (talk) 20:31, 5 November 2015 (UTC)

November 6

causes of limited access on wifi hotspot

OP curiousMahfuzur rahman shourov (talk) 05:22, 6 November 2015 (UTC)

Not sure what you are asking. Some possibilities:

A) Why is range so limited on WIFI hotspots ?

B) Why is access restricted on some WIFI hotspots ?

Are you asking one of these Q's, or something else ? StuRat (talk) 05:36, 6 November 2015 (UTC)

Perhaps he's enquiring as to whether certain sites are inaccessible (most likely the hotspot owner choosing not to serve "adult" content or similar for personal or legal reasons) or why speed/downloads are capped/restricted (most likely to reduce costs to the hotspot provider - free wifi is a courtesy mainly and abusing it with high bandwidth activity can be costly for the provider I would surmise). Unless of course he's having issues with the "limited connection" you get when there is a problem with your wireless connection to the hotspot, in which case he would need to consult technical support for the hotspot, his device or both. Quintessential British Gentleman (talk) 01:50, 7 November 2015 (UTC)

Assuming both questions are being asked and certain sites are restricted. The British Gentleman has sufficiently answered the question if this were just one hotspot. Assuming there is a connection problem with all hotspots, it would be logical that the device is the issue. Hotspots are very backwards compatible so the age of the device should not be a factor. You should be looking at the hardware or software to solve this issue. Depending on your device, you can download apps that will test the hardware and software. If there were any recent updates prior to the problem, undo them. If you dropped the device, the app should recognize the damage to the hardware. Tools like Speccy from Piriform are free and do an excellent job. I found several answers on the LG help pages for troubleshooting my phone. — Preceding unsigned comment added by Brnin60s (talk • contribs) 01:36, 10 November 2015 (UTC)

Seamless, High resolution, dark space images

Hello,

I am looking for some very specific types of images, and i can't seem to find anything regardless of my search terms. I need a few samples of different images that satisfy the following criteria:

• The content of the image must be of outer-space. This does help some in the "mostly dark" requirement below.
• The image is seamless. This means that if you tile the image vertically or horizontally, the left/right sides match, and the top/bottom match. Usually some of the objects in this type of image are partly on the top, and wrap around on the bottom... same for left/right.
• The image must be relatively high resolution. 1080p preferred.
• The image must be mostly dark, but have some interesting brighter areas.

Some images which are similar to what i am looking for:

Nebula 1 Nebula 2

... I would almost use these images, but the glaring issue is that these are not seamless. If i tile them, its obvious where the image begins to repeat. If it helps, i am wanting this for a subtle dark scrolling background in a main screen menu for some research i am doing in Unity Game Engine.

Thanks to everyone in advance for the help. Believe it or not, googling "Seamless galaxy images" in Google Images brings up lots of bras and photos of Galaxy5 phones!

216.173.144.188 (talk) 05:43, 6 November 2015 (UTC)

There is a fundamental problem with what you ask. The sky is most easily thought of as a sphere around the earth. The photographs you find out there online are rectangular. If you think about pasting rectangles onto the insides of a sphere, you soon realise that it's not possible to do that without overlaps or gaps. In fact, it's a topological property of a sphere that you can't do that...so what you're asking for is impossible. That said, you can approximate what you're after for a small area of the sky.

For a game, you either need something called a "sky box" - which is typically just a cube surrounding the world with six textures pasted onto it - or you need to compress your map into a circle and use a shader to reconstruct it. If can afford a small licensing fee, I strongly recommend going to a company at http://www.1000skies.com who specialize in high resolution pictures of the sky for movies and video games. Their work is stunningly good - and they've taken care of all of the wrapping and morphing needed to pack a high res sky image into a rectangular texture map. SteveBaker (talk) 15:48, 7 November 2015 (UTC)

You can get an image (I suggest one with just some stars in it). Then, open it in Gimp and select Filters:Map:Make Seamless. It will make the image seamless for you. 209.149.114.132 (talk) 14:50, 6 November 2015 (UTC)

Thank you! This is a most valuable answer, because it does not rely on the availability of something; I can make the image i desire myself! The key thing i am missing from many many of the images i do like is this seamless property. Thanks once again! Problem solved!

216.173.144.188 (talk) 19:37, 6 November 2015 (UTC)

And if you need source images, nasa releases high resolution hubble images to the public domain. Literally hundreds of awesome space images. That's what I use for all my wallpapers. Vespine (talk) 23:57, 8 November 2015 (UTC)

Nitpick from someone who's spent a lot of time reading about copyright law: they're in the public domain to begin with. Any work of the United States government is, by U.S. law, unable to be copyrighted. They're never "released" into the public domain because they're never copyrighted to begin with. --71.119.131.184 (talk) 02:34, 9 November 2015 (UTC)

Why Depth First Search uses linear space time?

I would like to know why the space complexity for Depth-first search is Ο(bd)?I have searched the web but it all tells about equations like (m-1)*(b-1)+b that I can't understand.Could anyone give an intuitive explanation with an example.JUSTIN JOHNS (talk) 08:08, 6 November 2015 (UTC)

Assuming b is the base and d is depth, if you search every item in a depth-first search, you will search about b*d items. If it is a well-balanced tree, you will search 0.5*b*d items. If you don't understand that, go back and look up how to calculate the area of a rectangle and a triangle in geometry. It is normal in O complexity to drop constants. In 0.5*b*d, the 0.5 is a constant. So, we drop it and get O(bd). 209.149.114.132 (talk) 13:24, 6 November 2015 (UTC)

b is the branching factor. The number of nodes at depths up to d is O(b^d), not O(bd), and in any case the question was about space complexity, not time complexity.

In fact the space complexity of DFS is O(n) where n is the number of nodes, or O(d) if you don't prune multiple paths to the same node. It's not O(bd).

The article on Iterative deepening depth-first search said that its space complexity is O(bd) but also that it's O(d). O(d) is correct, so I removed the O(bd) claim, which dates all the way back to the article's first version from 2004.

Outside sources that claim O(bd) may have gotten it from the Wikipedia article. -- BenRG (talk) 00:09, 7 November 2015 (UTC)

Bitcoin ransoms

I was reading https://protonmaildotcom.wordpress.com/ in which Protonmail admitted to paying DDOSers a ransom. Needless to say, it didn't work, and they published the address of the DDOSers ( 1FxHcZzW3z9NRSUnQ9Pcp58ddYaSuN1T2y ). What I don't understand is... I didn't think Bitcoins were truly anonymous. I thought each one was a number, a solution to some kind of math equation ... isn't it? So why can't Protonmail publish the list of actual bitcoins they paid for the world to see? Then if those bitcoins ever turn up again, people know they were through the extortionists' hands, right? (OTOH maybe the chain of transactions written for Bitcoins already has the address they published coded into it? I don't know the details)

I still don't *really* understand how Bitcoins are protected against double-paying two different people, but if the extortionists try to spend a Bitcoin, the receiver will want to check it. Can't that check be spotted and flagged - whether by the receiver or the party doing the check - to set off an alarm?

I understand if there are a lot of people who say they're just not going to report any crime, whatever it is, then Bitcoins might be safe to use. But the same is true of cash. But even if the guy you pay cash to doesn't look up the serial numbers, eventually someone will, and then there will be a swarm of agents following the trail backward. Isn't that true for Bitcoins also?

What am I missing here? Wnt (talk) 16:44, 6 November 2015 (UTC)

Bitcoins don't have serial numbers. The Bitcoin network is just a transaction log. Each transaction has the form "take the money from these previously-unspent outputs of previous transactions, and distribute that money amongst these new transaction outputs." What makes a particular transaction output (TXO) yours is that only you know how to satisfy the cryptographic spending criterion that's attached to it (probably because you have a private key corresponding to the public key it uses). That spending criterion is only meaningful until you spend that TXO (and define new criteria for the new TXOs).

If you tried to taint the descendants of a particular TXO, the taint would spread because transactions can take money from multiple sources. For example, if a transaction takes 1 BTC that's tainted and 1 BTC that's untainted and redistributes it as 0.5 BTC each to four outputs, you have to decide whether the amount of tainted money just doubled, or the outputs are each half as tainted as before, or two unlucky recipients (which you'd have to choose at random) got tainted money and the others are okay.

Worse, if the tainted money was deposited in a Bitcoin bank, there's no longer anything in the public Bitcoin log that says what the offenders turned it into. Even if they withdrew it as BTC shortly afterwards, it probably came from a different, untainted TXO owned by the bank, and all future recipients of the tainted money are innocent victims.

If law enforcement had access to an up-to-date list of TXOs owned by banks (so they knew when the money was deposited in a bank) and could demand that the bank turn over its internal records of where the money went after that, they could possibly trace it. I don't know to what extent that's happening in reality. Obviously the international nature of Bitcoin makes it difficult. -- BenRG (talk) 18:46, 6 November 2015 (UTC)

@BenRG: I wasn't actually thinking about recovering funds, but finding the extortionist. From that point of view, either of the BTC's derived from a particular TXO would give authorities a chance to haul that recipient in and ask him where the BTC came from. (Or am I still confused?) And I assume a Bitcoin bank can't be entirely anonymous/unfindable or else ... why don't they just vanish one fine day and disperse their funds as their own money rather than returning it to depositors? Wnt (talk) 20:27, 6 November 2015 (UTC)

Yes, if they can identify the owner of any downstream TXO, "bank" or not, they might be able to trace that back to the original offender one transaction at a time. I agree that people shouldn't trust a Bitcoin "bank" without some kind of accountability, but it's their money and a lot of them trusted Mt. Gox, so who knows. One thing a bank could do to increase trust is publicly pay all its Bitcoin to itself periodically to prove that it still controls it. That wouldn't prevent the owners from skipping town with the money one day, but might allow law enforcement (or anyone else) to identify deposits to that bank in the block chain. -- BenRG (talk) 22:48, 6 November 2015 (UTC)

Also worth noting is that most of these ransom schemes, and online computer crime in general, are based in Eastern Europe or mainland Asia, where law enforcement doesn't care, and is often inept anyway. Bitcoin is being used here more for the quick and unregulated funds transfer than the anonymizing aspects. --71.119.131.184 (talk) 06:30, 7 November 2015 (UTC)

The more I think about it, the more this seems prone to regulatory action. If a Bitcoin necessarily contains a TXO chain that includes a traceable attestation that it was once used in a ransom, then it seems pretty obviously to be some kind of stolen/forfeitable property... no matter how many were mixed in what proportion to make it that way. At best the owner might hope to recover a portion by filing suit (and putting up a 10% bond first) under U.S. notions of civil forfeiture. A prosecutor using this sort of action could surely say that a Bitcoin owner "knew or should have known" that the provenance on his coin included markings showing it had been spent as ransom in the past - and the flip side of this is that I'd expect online websites to pop up that can "scan" a bitcoin's history against all known ransom transactions. Such a website would seem like a good business model because the moment it is available it becomes obligatory, according to the known-or-should-have-known model. Wnt (talk) 12:58, 7 November 2015 (UTC)

If everyone knows or should know which transactions are tainted, then the criminals know, and can just demand as part of the ransom condition that the payment not be tainted. If you wait and taint it later, whoever has the money at that point is screwed, because they couldn't reasonably have known not to take it, but now they can't get rid of it because no one else will take it. -- BenRG (talk) 23:08, 7 November 2015 (UTC)

Well, I still don't truly understand how Bitcoins work, but I assume that you can't just transmit one of these TXO records that says "I received 1000 bitcoins, honest"; there must be some kind of proof you received particular ones. Is this code (1FxHcZzW3z9NRSUnQ9Pcp58ddYaSuN1T2y) actually embedded as one of the 'previous transactions' in the blockchain, readable by anyone who cares to look? If not, are there other unique identifiers that could have been retained by Protonmail that could be looked for?

As for the moral argument, yeah, it applies, but .... police are under no obligation to keep Bitcoins valuable. Some guy invented Bitcoins in his head - nobody ever guaranteed they were worth something. Police are under an obligation to stop extortion. I think this means that yes, some people who receive Bitcoins are going to get screwed. However, I imagine that they would arrange something whereby they could cooperate with the extortion investigation, possibly paying a portion of the bitcoin in compensation, and then get their particular bitcoins 'whitelisted'. For example, if a bank did the thing suggested above where they reissued all the bitcoins with a commingled history, they'd have to pay back the whole ransom, but then all their bitcoins would be circulable again. OTOH, if no whitelisting is done, then taking Bitcoins out of circulation permanently might make the others more valuable, which would just contribute a bit more volatility/risk to an already volatile/risky investment. Wnt (talk) 13:04, 8 November 2015 (UTC)

Bitcoin transactions are valid if the total amount of the inputs equals the total amount of the outputs. A 2+8→1+9 transaction is accepted by the network because 2+8=1+9. Any TXO can be spent only once, in its entirety; if you want to send a fraction of that amount to someone, you send the rest to a new TXO owned by you (your "change"). The transactions are nodes and the TXOs are edges of a flow network (with fixed acyclic flows). If you introduce red dye into one of the pipes, eventually a large fraction of the downstream water will be reddish. As an actual example, most U.S. currency has traces of cocaine not because most of it has been used illicitly but because the contamination spreads from note to note when they're handled together.

You can absolutely identify Protonmail's ransom payment in the transaction log, and all downstream transactions. But imagine if the ransom was paid in $20 bills, the criminals deposited it in a bank, the bank put it in their ATMs, a random client of the bank withdrew $60 from an ATM, and then they couldn't spend it until they told the police everything they know about the ransom payment. That's how cash works. People ignore the serial numbers and BTC transactions histories and treat it as fungible. Making people liable for the transaction history of paper currency would fundamentally change the nature of cash. It probably makes sense for the police to deal privately with BTC banks and exchanges to track criminal activity, but the self-destruct system you're proposing is not a good idea. -- BenRG (talk) 20:52, 9 November 2015 (UTC)

.NET C# question about HTTP and HTTPS

I recently got a bug report from customer on-site testing at work. An ASP.NET web application I had worked on wasn't able to open one of its pages.

It turned out that the link to open it was using a plain HTTP URL scheme, whereas the customer on-site installation was deployed under HTTPS.

What puzzles me here is that the code should already have worked this out. It uses the Request.Url.AbsoluteUri property, which should have worked out the correct scheme. But it did not. I added a check that if Request.IsSecureConnection is true, then it uses the HTTPS scheme on the link, but that didn't work either. In the end I resorted to hard-coding the link scheme as HTTPS.

The testing engineer told me that if the site was accessed directly from its own web server, it worked OK. But if it was accessed from anywhere else, it kept writing the link as HTTP even though the site was deployed as HTTPS.

What is happening here? Is this supposed to work like this? Or is there something I don't understand here? Or is this a bug in the actual .NET libraries? JIP | Talk 19:59, 6 November 2015 (UTC)

November 7

Youtube offline for smart mobile phones

Does anybody know how the 'Youtube offline' works on 'smart mobile phones'? Could someone show me how I could use the same method via PC? -- Space Ghost (talk) 03:39, 7 November 2015 (UTC)

Presumably it downloads videos and saves them for later viewing. youtube-dl is a popular program to do the same thing. There are others as well. --71.119.131.184 (talk) 06:11, 7 November 2015 (UTC)

You don't even need another program. KeepVid [10] and similar sites just use your browser. In the past, you generally needed to use a Java applet (so did effectively need an a program) but AFAIK this generally isn't needed for YouTube nowadays. Nil Einne (talk) 06:47, 7 November 2015 (UTC)

Don't want to download guys, I'm on 'pay bit as you go'. Check this out, this will give you an idea of what I'm searching for. I'm in need of this, very very important for my boring life. -- Space Ghost (talk) 21:23, 7 November 2015 (UTC)

Offline viewing works by downloading the videos in advance. If you can't afford to download the videos then you can't watch them offline. You also can't watch them online since that downloads them as you watch. -- BenRG (talk) 02:21, 8 November 2015 (UTC)

How do you think the video gets to your computer (cell phones are computers)? You're always downloading the video from YouTube's servers. This seems to be a common misconception some people have, that "streaming" is somehow completely different from "downloading". The only difference is that a "streaming" video player (like the one on YouTube pages) doesn't save the downloaded data to permanent storage. --71.119.131.184 (talk) 08:27, 8 November 2015 (UTC)

Yeah as BenRG and 71 say whether your streaming or retrieving for offline viewing, both will need to download the file and neither intrisicly save data. Offline viewing would actually often use more data because many people aren't going to watch everything they downloaded for offline viewing. And if you skip through the video to a certain point, it's possible your player won't have downloaded the previous portions if you're streaming (but you would have downloaded the whole thing for offline viewing). Plus a smart offline viewing application will probably choose a resolution close to your device resolution; which the online viewing/streaming also normally tries to do, but the streaming will often reduce quality if your device is having trouble handling it. On the flip side, caching tends to be limited so often if you watch the video again and sometimes even if you rewind a bit, you may end up needing to download from that point again when streaming. And if you're manually downloading, you can probably choose a lower resolution easily. (On the desktop, you can normally also easily choose resolution, but apps seem to be more reluctant to give that level of control.)

The cases when offline viewing may save costs (as opposed to data) would be if you download for offline viewing over wifi that you either don't pay for (i.e. free public wifi or similar) or you do pay for but at a lower rate (e.g. a fixed line connection); but when streaming you will need to use more expensive mobile data. Also if you use the same connection as for streaming (be it mobile data or wifi), but the costs depends on time of day (or whatever) and you download for offline viewing when it's cheapest but may not watch streaming content at the cheapest rates.

Technically it's possible whoever is providing the offline viewing app could work with the network provider (or are the network provider) to charge downloads for offline viewing at a lower rate (perhaps because the app is designed to be network load aware) but I don't think that's particularly likely. The primary reason for offline viewing in some developing countries is likely because the connection coverage there is more spotty, and also slower even when it exists so streaming is more problematic. (Things like Facebook Zero and Wikipedia Zero and similar initiatives exist, but these tend to be low bandwidth services and also aren't offline oriented. Some providers do offer unlimited Youtube, but this is usually at an additional cost and directed at streaming anyway.)

Nil Einne (talk) 17:56, 8 November 2015 (UTC)

Its the T.V. adverts, and someone showed me in their smart phone, telling me what I told you guys. I did not believe them at first, I was hopeful because the offline thing works where I'm currently based. That's why I was more exited...

Thank you all anyway, for teaching me a bit too guys. Regards. -- Space Ghost (talk) 18:36, 8 November 2015 (UTC)

IT Graduate Development Programme Job Questions

So, I applied for an "IT Graduate Development Programme" Job with Dell that was forwarded by my college and got this reply:

You will be contacted by a representative from our team for a 15 minute (maximum) phone screening conversation. This conversation will provide you with information about Dell. We will also have 7 general, very basic questions for you.

I would like to reiterate, this is not an interview. This is very much a screening process and a means for you to get some valuable information on Dell.

My question is, does anyone have any idea what types of questions I can expect? Are these likely to be technical or programming questions?

Thanks, 2A02:8084:9360:3780:413C:2B61:770B:88F2 (talk) 16:10, 7 November 2015 (UTC)

These kind of things are usually a "pre-screen" - they're there to cut out people who an actual interviewer would know weren't going to be right for the job within the first minute of the interview. This kind of thing avoids them wasting their time (interviewing for a position takes a lot of people a bunch of time) and yours (you coming down there for an in-person interview, only to discover they're looking to fill an entirely different job than what you're looking for). Some typical reasons for these kind of misunderstanding and time-wasting scenarios, which the pre-screen is trying to avoid, are:

• they're actually looking for a senior person, and the bonehead recruiter has sent them a bunch of college graduate resumes.
• the recruiter (I don't mean to rag too much on technical recruiters, but I've seen some really useless ones) has simply keyword-searched the positions vs candidates - so you get someone who is a graduate in computer science (meaning software and maths) being matched for a job as a computer engineer (meaning designing computer hardware with logic elements or IC packages)
• some applicant is suffering from some major Dunning-Kruger, and is calling themselves a "C++ expert" because they finished the entry-level Udacity C++ course last week
• the applicant is obligated to apply for jobs (e.g. to continue to be eligible for government benefits) and is doing so wily-nilly; and the company is obligated to give everyone at least a rudimentary screen (again for some legal reason, like recent layoffs) and say why that specific person isn't suited. I once pre-screened people for a senior Java development position, and one guy had a degree in environmental science (and a bunch of related experience, I think to do with hydrology). Once it was clear that he wasn't experienced with Java, software development, or embedded systems, we had a nice chat about beavers.

So you can really only "fail" a pre-screen if somehow wires are crossed somewhere, and it's not a job you'd actually get (or want to get) in an actual interview. -- Finlay McWalterᚠTalk 16:39, 7 November 2015 (UTC)

For those unfamiliar with the term: Dunning–Kruger effect. I would also expand on Finlay's excellent answer a bit: this job might be something you're really not interested in, but thought you might be because companies are sometimes hamstrung by what HR/legal says they can put in the ad. This is a good time to ask one or two pointed questions about what the job really is about - that's what they mean by 'find out about Dell' - you're presumably already aware of the company :-) 99.235.223.170 (talk) 21:22, 7 November 2015 (UTC)

I had a cubicle between two phone-interviewers when I worked for a government contractor. Being government funded, they didn't want to hire Americans. They only wanted programmers from India and China. The interviewers asked them basic questions, such as "what is a pointer?" and "what is a buffer overflow?". They had enough of an idea of the answers to know if the applicant was saying something reasonable. It turned out that at least half of the PhD-level applicants failed the basic phone interview and never made it to the real interview to see how well they could program. I was lucky that I made it through the initial interview, a real interview, and then they flew me to San Diego for the final interview and I was hired. 209.149.114.132 (talk) 12:28, 9 November 2015 (UTC)

It is very variable between companies - I've applied for jobs with six figure salaries and been asked "What is the biggest number you can store in a byte" and stupid stuff like that on the phone screen. On the other hand, I've also worked places where there is no script for the interviewer at all and you just chat about whatever (s)he fancies talking about. But as others have said - you shouldn't stress about it. If this is a job that you come within a million miles of getting, you won't fail the initial phone screen - it's there to get rid of people who have absolutely no clue and who should never have applied for the job in the first place. Subsquent interviews (which might also be on the phone or via Skype) will likely be the harder ones - expect at least one face-to-face interview after that. But the whole process is incredibly variable. My previous job needed one phone call and a 30 minute interview (at which they actually offered me the job, haggled over salaries and settled it all on a handshake) - but then my current job took five separate, hour long phone calls, then a gruelling 8 hour back-to-back set of 30 minute grillings by different team members...ending with a quiet stroll to the local Starbucks with my future boss...and then a nerve-wracking four week wait for an actual job offer! SteveBaker (talk) 22:01, 9 November 2015 (UTC)

November 8

Online maps for vertigo-safe roads ?

I have vertigo and get dizzy when the landscape falls away from under me as I drive, which is dangerous. Is there an online resource that would show me which roads I can take that are vertigo-safe ? That is, they have a flat plain on both sides of the road ? (In general, going through mountains is a problem, but roads that go through tunnels are far better than those which hug the edge.) I suppose I could go over a contour elevation map superimposed on a road map and eventually figure it out, but I'd much rather have roads colored green, yellow or red to show degree of danger. StuRat (talk) 00:46, 8 November 2015 (UTC)

I should add that roads and bridges can be "vertigo-safe" if they have barriers on the sides that block the view of the depths below. On the other hand, expansion cracks in bridges that let you see the water below are bad for vertigo. StuRat (talk) 19:30, 8 November 2015 (UTC)

That seems like a tough thing to discover. Google maps does not include such thing, and I don't believe many people would have the same problem. Maybe you could avoid bridges all-together, or, let someone else drive, or, use the sun visor to block the view. --Denidi (talk) 00:12, 9 November 2015 (UTC)

The only one of those with any possibility is blocking the view, but the difficulty of blocking and unblocking the view quickly, while driving alone is quite a problem. Maybe some kind of blinders that could be flipped up and down on both sides of my sunglasses might work ? StuRat (talk) 05:22, 9 November 2015 (UTC)

How do I type weird letters in Xubuntu Linux?

For example I want to type Fëanor with double dot on top of the e letter, or Andúril with the top accent u, and what is the correct term for that kind of weird character thingy? 139.193.247.7 (talk) 05:58, 8 November 2015 (UTC)

Take a look at this or this. In short, you configure one of the keys on your keyboard to be a Compose key, using the Keyboard Layout options under System Settings. You can then use that key in combination with others to generate many different accented and other special characters. For example, to generate a "ë", you could could type Compose+"+e. -- Tom N talk/contrib 06:37, 8 November 2015 (UTC)

Well it works, so now I don't need to copy paste words from google anymore

Resolved

139.193.247.7 (talk) 10:03, 8 November 2015 (UTC)

And to answer your question about what they're called... The first is an umlaut. Dismas|^(talk) 19:35, 8 November 2015 (UTC)

An umlaut (diacritic) rather than an umlaut (linguistics), to assist disambiguation. Tevildo (talk) 20:13, 8 November 2015 (UTC)

Some would prefer to call it diaeresis; Germany adopted it as an imperfect imitation of a mark already used to represent umlaut. —Tamfang (talk) 20:22, 8 November 2015 (UTC)

In general, marks that distinguish variants of a base letter are diacritics. —Tamfang (talk) 20:22, 8 November 2015 (UTC)

How can Skype run with Ubuntu on a windows computer?

I have 2 windows computers with Ubuntu which is anti-virus software and I need my brother to set up Skype because I talk to my friend a lot through Facebook and on the phone. She lives thousands of miles from me and when I use a computer I open several tabs and my brother set up my computers so I don't get virus. He says Skype can't run with Ubuntu. Please give some computer advice. 209.53.181.75 (talk) 22:44, 8 November 2015 (UTC)

Ubuntu isn't anti-virus software, it's a Linux distribution. It's not clear what operating system your computers are running—Windows or Ubuntu, or both? If you are running the Ubuntu operating system, Skype is available for Linux (and for Windows of course). --Canley (talk) 06:03, 9 November 2015 (UTC)

That site only gives a version suitable for Ubuntu 10.04, not the latest version. I've checked in the software centre, since installing Ubuntu on my Mac via Parallels, and it is not available. KägeTorä - (^影_虎) (もしもし！) 07:29, 9 November 2015 (UTC)

Actually, there's instructions for installing it on Ubuntu Palmtree5551 (talk) 17:12, 9 November 2015 (UTC)

November 9

http://adadvisor.net/adscores/g.js?sid=9276253823

I keep getting a script error saying that a script from http://adadvisor.net/adscores/g.js?sid=9276253823 is not working, would I like to keep running it or not. The problem is very recent compared to the age of my computer and the last reboot of my OS.

I run windows 7 on a Gateway NV78 laptop. The problem seems to be occurring whether I am using IE, Firefox, or Chrome, although I am not exactly sure if it corresponds to one of these browsers specifically.

I have run AVG, emptied all my caches and rebooted a few times. The problem continues. The best advice I can find via googe is to turn off my windows script error notifications, which sounds insanely unhelpful.

Can anyone suggest what's going on and how to fix it? Could it be a file on my desktop or some other problem? Who the hell is http://adadvisor.net/adscores/g.js?sid=9276253823? I am already insane, but this is slowly driving me into even deeper levels of Lovecraftian madness.

Thanks. μηδείς (talk) 03:42, 9 November 2015 (UTC)

Looks like code to control which ads you see. So, you surely don't need it. When exactly does it get called ? StuRat (talk) 05:17, 9 November 2015 (UTC)

To rephrase the above for understanding, is this just happening randomly, or only when you go to certain Web pages? Does it happen whenever a browser is open? General advice for getting help: remember, we can't see your screen. Screenshots are often helpful (just remember not to include any information you don't want public). --71.119.131.184 (talk) 08:52, 9 November 2015 (UTC)

Have you tried restoring your PC? Note: Don't if you are not good at handling PC; most of the time the restoring points are linked with other softwares. Also remember that restoring always creates problems starting from the first time you do it. Now:

1)Check your 'uninstaller program window' and check the 'restoring point window', see if you find this rubbish. If not uninstall the web browsers, but first 'right click' the browsers 'shortcut' icon, go to 'properties' and or open its file/folder location. Delete the files and folders of the browser(s) thereafter uninstall is complete. If wished: After you uninstall the browsers, ensure you delete its folders and sub-folders from 'AppData' Folder. Delete the browser's hierarchy available in the PC (recommended for professionals because some files are requisites). Use CCleaner (or something), reboot, reinstall the web browsers... If it doesn't work and you choose to use restoring point window, make sure you keep a Windows OS CD handy for the near future.

2) Just follow the advice on how to delete the code, if possible. I'm sure someone will assist you in a step by step manner. -- Space Ghost (talk) 10:31, 9 November 2015 (UTC)

Adadvisor.net is owned by TARGUS information corporation [11]. They are "... a leading, independent provider of real-time, on-demand information and analytics services including Caller ID..." [12]. Which makes it sound a lot like they are shadily trying to collect your browsing info without your express consent. I don't know what the problem is, but I'd generally advise the use of NoScript to keep malicious javascript from messing with your computer. That will solve this and many other issues, at the cost of having to whitelist pages that you trust. SemanticMantis (talk) 16:01, 9 November 2015 (UTC)

"Virtual" email address?

For many years I've had a domain name which I'll call "xxx.net" for privacy reasons. I have a small website and email servers at xxx.net, and my primary personal email address is me(at)xxx.net. The website is no longer worth the recurring cost of the domain name and the hosting, so I'm considering dropping both, but I don't want to change my email address if that can be helped. Is there some way to pull this off? 68.97.47.26 (talk) 13:27, 9 November 2015 (UTC)

If you stop renewing the registration of the domain name, then anyone else can take it over and intercept your emails. Your registrant might allow email forwarding without hosting, or you can move the registration to a registrant that does allow this. You can then spoof the "from" field when you send emails from any other free email address. I don't think there's any way to achieve what you require at zero cost, but xxx.net can be registered at very low cost (.net isn't the cheapest of domains to register, but perhaps as low as $10 per year if you shop around). Dbfirs 13:47, 9 November 2015 (UTC)

Seconded. If you want to keep the email address, you'd at least have to keep the domain name. Most big domain name hosts (GoDaddy, etc.) offer some sort of email package directly through them, and I'm willing to bet you can mark it as forward-only for a very low price, if not for free. This would simply forward all email sent to that address to another email address of your choosing. As for the cost of the domain name itself, most are only like $15 per year. RegistryKey^(RegEdit) 13:53, 9 November 2015 (UTC)

The idea that the new domain owner might be helpful and forward your email is a definite long-shot. The (many) domain names I've owned for short-term reasons and left to expire have all been bought up by domain name squatters within weeks of me abandoning them. Those organizations presumably think that I forgot to renew - and then pester me to buy the domain back for some outrageous fee. Those are clearly not very nice people - so I'd be absolutely astounded if they'd be of any assistance to you whatever.

It's also possible that nobody will buy your domain name - and when it lapses, your email will simply stop working.

A third possibility is that somebody will buy the domain - but will not want to make it appear that you are an employee of XXX-corp by letting you continue to use joe@xxx.com because of the huge risk that you might say something inappropriate online and people would think that they had said it. So all in all, you don't have a snowball's chance in hell of getting someone to be that helpful to you - and certainly not without a prolonged break in service while they get their site set up and mail-servers running - during which you'd get no email.

If you want to keep your email address - then you very definitely need to keep ownership of the domain name...which, as others have pointed out...ought to be very cheap if all you need is email and a one-line HTML file saying that your site is no longer available.

SteveBaker (talk) 21:41, 9 November 2015 (UTC)

Crypto-currency Mining

How profitable can crypto-currency mining of currencies like Bitcoin, Litecoin, Dogecoin, Peercoin, etc be if I can source all the electricity I need for free?--Lukepeters36 (talk) 19:04, 9 November 2015 (UTC)

Even with free power, you'd still likely need to invest in dedicated mining hardware, like FPGAs and ASICs, if you actually wanted to turn a profit. And those aren't cheap. 67.133.155.66 (talk) 19:33, 9 November 2015 (UTC)

Is this primal-general-simplistic axis accurate?

I'm just starting to learn some JS programming. I never did porgramming before and never studied even half a course in computer science. Trying to arrange my humble knowledge into a frame, I created for my self a primal, general, and simplistic axis that describes the main stages from the electricity in the Hardware, to the JS on the screen. Please tell me if I am wrong anywhere, in the most simple words you can:

Program.

^

One or more programming language(s). Usually high, in this level.

^

--- optional ---

Database (DB).

^

Server-proxy (If there is one!).

^

Server.

---

^

OS shell 1 (CLI) || OS shell 2 == GUI.

^

Operating system [OS].

^

One or more programming language(s). Usually low, in this level, and surly in the levels under it.

^

One of the assembly languages.

^

Assembler.

^

Machine code (MC). Usually binary.

^

Electrical processes in the chemical hardware, bootstrapped and maintained by the nature of the hardware by a given electrical current.

Thanks, Ben-Yeudith (talk) 21:43, 9 November 2015 (UTC)

Unfortunately, we don't appear to have an introductory-level article on this topic. Operating system#Components and Kernel (operating system) aren't quite as impenetrable as most of our Computer science articles. Tevildo (talk) 22:06, 9 November 2015 (UTC)