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July 9

What is the halting problem about? How it is defined.

What is the definition of halting?
1-it will generate some loop
or
2-The machine would NOT be able to compute the input.168.227.189.254 (talk) 13:00, 9 July 2025 (UTC)[reply]

See halting problem. If you have further questions after reading that, come back and ask. 196.50.199.218 (talk) 13:22, 9 July 2025 (UTC)[reply]

The halting problem is defined as using a Turing machine, which is a formal abstract model of any computer program, to determine whether another Turing machine will halt, meaning whether a computer program will exit because it has completed its calculations. That is, can a computer program be written that will verify that another computer program will exit, as opposed to going into a loop? The answer is no. Turing showed that the halting problem is an undecidable problem. You can't write a program that will reliably determine whether another program will run to completion or enter a loop. This was one of the first cases of a proof that a problem is undecidable. The proof of undecidability is sort of a self-referential trick, but is logically sound in showing a limitation of logic. Robert McClenon (talk) 21:41, 9 July 2025 (UTC)[reply]

Bit tangential: Ever since I've first learned about this, I've wondered whether what I call the "restricted halting problem" can be solved: Can there exist a program (via a Turing machine) that can determine whether another program (via a Turing machine) will halt unless said program is the exceptional case featured in the proof by contradication? Aaron Liu (talk) 17:52, 11 July 2025 (UTC)[reply]

You may be interested in Busy beaver, that looks for the longest running machine that stops. Some simple cases can be determined simply. If you had a limit on the size of the program, perhaps the halting problem could be solved in theory (but not in practice). Graeme Bartlett (talk) 23:59, 11 July 2025 (UTC)[reply]

No. The proof by contradiction symbolically proceeds as follows. It gives an effective method to transform programs into other programs. Input program X, output program F(X). Now assume a program P exists that solves the halting problem: input program Y, output P(Y) = 0 if Y doesn't halt, and P(Y) = 1 if it halts. Still assuming such a P exists, we can run P on the program F(P). By the way F has been constructed, however, we know that F(P) halts if and only if P(F(P)) = 0, which, by the assumption, means that F(P) doesn't halt. This is a contradiction, so we conclude that the assumption was false.

The "exceptional case" you seek to exclude is the program F(P). To construct F(P) we need to have P first. But we have just shown that P is impossible; no such P exists, so the exceptional case does not exist either. ‑‑Lambiam 04:23, 12 July 2025 (UTC)[reply]

At some time, which I think was in the 1990s, someone advertised a BASIC program that was known as the BASIC Infinite Loop Finder (BILF), which would scan BASIC programs and determine whether they had infinite loops. A columnist bought the BILF, and switched the two outputs, just as Turing had described, and fed the revised BILF into the original BILF. He then reported that more than 48 hours later, it was still running. Robert McClenon (talk) 00:20, 13 July 2025 (UTC)[reply]

Turing's construction is not nearly as simple as switching two outputs. ‑‑Lambiam 06:23, 13 July 2025 (UTC)[reply]

In 2008, I was reviewing a set of requirements, and one of them said, essentially, "The program shall not 'freeze' on encountering an error condition." I said that this was an untestable requirement, because it could not be verified by inspection, by demonstration, or by analysis. It was a reasonable criterion, that if the program 'froze' on encountering an error condition, the tester could fail the test. However, it was not a testable requirement and so could not be in a checklist of requirements to check off in acceptance testing. It could not be verified by demonstration, because it was not feasible to subject the program to all possible sets of inputs. It could not be verified by analysis, because that was equivalent to the halting problem. Robert McClenon (talk) 00:20, 13 July 2025 (UTC)[reply]

The unsolvability of the halting problem applies to a decision procedure that works on all programs. For any given specific program, it may very well be possible to give a rigorous proof that it cannot get into an infinite loop, so having this as a requirement is about as reasonable as requiring that its output is never blatantly wrong (which is, in general, also undecidable). ‑‑Lambiam 06:30, 13 July 2025 (UTC)[reply]

So the halting problem is not purely academic. Robert McClenon (talk) 00:20, 13 July 2025 (UTC)[reply]

July 12

Free Images

Has anyone any thoughts on genuinely "copyright free" image libraries? Googling used to produce them in the good old days but searching now produces a whole first page of subscription services, which of course is literally the opposite of what I'm looking for.

If it affects the answer:

This is for a non-business use; also
Nothing to do with using on Wikipedia. AndyJones (talk) 15:51, 12 July 2025 (UTC)[reply]

Our sister project Wikimedia Commons hosts millions of freely usable images. Here are some sites with copyleft images, mainly photos:

Several free GenAIs create images on request. ‑‑Lambiam 19:24, 12 July 2025 (UTC)[reply]

Note that Commons is also copyleft because it uses a share-alike license. Aaron Liu (talk) 19:38, 13 July 2025 (UTC)[reply]

Brilliant. Thank you. AndyJones (talk) 12:24, 18 July 2025 (UTC)[reply]

July 13

NSFW Nock?

The Internet Archive is not censored, therefore it is understandable that certain search terms may return content considered inappropriate for various reasons. If I search for "Oswald Nock" (without the quotes), however, I felt fairly sure to remain within the bounds of common decorum. What I actually get listed is:

64 texts, all authored, co-authored or edited by O. S. Nock, which is what I expected
1 item of 'software' unrelated to that author, but containing in its metadata both the words 'oswald' and 'nock'; unexpected but understandable
5 movies of an obviously NSFW nature (and duly flagged as such) whose metadata contain neither 'oswald' nor 'nock'

This outcome is repeatable, and occurs whether or not I am logged in to the archive.

Why are these five movies listed in the search results? -- Verbarson ^talk_edits 18:10, 13 July 2025 (UTC)[reply]

I don't know, but I can confirm it's repeatable. The five films are all French, but AFAICT, there's nothing in the French (or the translation to English) that comes out to Oswald or Nock. I'm flummoxed. As a sidebar, I'll also note that IA's definition of "soft porn" is different than most, so their data labels are open to question. Matt Deres (talk) 20:39, 13 July 2025 (UTC)[reply]

In which direction, out of curiosity? Asking for a friend. --Trovatore (talk) 21:37, 13 July 2025 (UTC) [reply]

Well, one film opens with a woman sucking a dick. Just... you know, going at it like a trooper. Which is all well and good, but I think most people's definition of soft porn probably wouldn't include that. They then switched to fucking in a slightly more discreet manner, but since the scene failed to include a mid-century railway engineer, I moved on. :-) Matt Deres (talk) 01:55, 14 July 2025 (UTC)[reply]

Hey, no kink-shaming here. I'm sure that striped hat does it for lots of folks. (Or is that a conductor? I get confused.) --Trovatore (talk) 02:45, 14 July 2025 (UTC) [reply]

Ossie Nock was English; striped hats were not a feature of UK railway culture (and 'conductor' was not a usual term for the train personnel we call 'guards'). Just sayin'. {The poster formerly known as 87.81.230.195} 94.5.172.125 (talk) 04:46, 14 July 2025 (UTC)[reply]

July 14

What ASCII characters are borders?

I have this memory of seeing a list of ASCII characters in a computer science class where some could be used to create borders around text. So far I haven't found anything online that fits. Some of the border characters looked like the letter L but might be backwards or upside down or both. Then there were the ones like the letter T, which could be upside down or turned on the side.— Vchimpanzee • talk • contributions • 23:33, 14 July 2025 (UTC)[reply]

You are perhaps thinking of Box-drawing characters#DOS (the article covers other operating systems as well).-Gadfium (talk) 00:58, 15 July 2025 (UTC)[reply]

That's the one. Thanks.— Vchimpanzee • talk • contributions • 16:06, 15 July 2025 (UTC)[reply]

ASCII was a 7 bit character set, so only codes up to 127 and so a bare minimum of characters. When the IBM PC was introduced, it now had a mostly clear 8 bit path for characters through the BIOS, so they produced several 8 bit sets, with up to 255 characters (Many computer makers and developers did this, not always consistently). But because the IBM's set were well thought out to include a useful box-drawing set with both single and double lines, and even the combinations. For a decade (until Windows dominated) this was a big thing in desktop software design. They were stored in Code page 437, although there were other ways to access them too. Andy Dingley (talk) 17:22, 15 July 2025 (UTC)[reply]
Anyone else remember IBM TopView, a text-based windowing interface from the 80s that made use of those box characters? -- Verbarson ^talk_edits 07:35, 17 July 2025 (UTC)[reply]

July 16

Internet before social media

Prior to 2010s, what does the Internet look like before social media? Why does social media spread faster than other Internet options, that are email and FAX? 2600:387:15:4918:0:0:0:7 (talk) 11:59, 16 July 2025 (UTC)[reply]

Social media didn't only exist in the 2010s. Myspace started in 2003, and if you count big chatrooms Usenet and IRC also existed for a long time. Aaron Liu (talk) 12:48, 16 July 2025 (UTC)[reply]

@Aaron Liu I agree with you. 2600:387:15:4918:0:0:0:7 (talk) 18:34, 17 July 2025 (UTC)[reply]

July 17

Time Travel Story Timeline Tool

I want to make a plot or map of characters in a timeline story. It is complicated like Primer. Is there a tool that helps with this instead of simply trying to draw it in Photoshop? 4.17.97.234 (talk) 11:29, 17 July 2025 (UTC)[reply]

Something like this? https://xkcd.com/657/ 196.50.199.218 (talk) 13:48, 17 July 2025 (UTC)[reply]

Yes. I want to make a timeline like that, but this timeline story has 12 unique timelines and 28 unique characters that move from timeline to timeline... I think that there is one who never moves, but for the most part, they all move at least once. Trying to make sense of who is in what timeline at what point is confusing. 4.17.97.234 (talk) 15:56, 17 July 2025 (UTC)[reply]

You might be able to model it in MS Project as long as there isn't a temporal paradox. The characters could be a resource needed in various timeliness. 156.155.17.219 (talk) 16:37, 17 July 2025 (UTC)[reply]

MS Project includes (I understand) Gantt charts, for which there must also be several other available software applications. Being old-school, however, I still think it's easier to do things like this by hand on large sheets of graph paper. {The poster formerly known as 87.81.230.195} 94.5.172.125 (talk) 14:04, 18 July 2025 (UTC)[reply]

July 18

Questions About New Outlook and "Focused Email"

I have some questions about New Outlook with Microsoft Office. First, can someone provide me with a link to a paper or web site by Microsoft that explains why they have rolled out New Outlook, what they think is better about it, and why they are so determined to make it difficult to use Classic Outlook? Second, I have had New Outlook installed, because Classic Outlook stopped working, and now it displays something called Focused Email, as opposed to Other Email. What does it think Focused Email is? Do I have any control over what it focuses on? Third, is there an economic reason why New Outlook is beneficial to them? I may have more questions, but I think that is it for now. Robert McClenon (talk) 19:38, 18 July 2025 (UTC)[reply]

https://support.microsoft.com/en-us/office/getting-started-with-the-new-outlook-for-windows-656bb8d9-5a60-49b2-a98b-ba7822bc7627 is what MS thinks is better about New Outlook, and I personally think they want everyone to switch over just so they can drop support work for Classic Outlook and have the Classic Outlook engineers reprioritized or fired. Aaron Liu (talk) 20:27, 18 July 2025 (UTC)[reply]

July 19

stopping youtube autodubbing on browser on phone

Hi friends, like the title says. I watch lots of videos on my browser on the phone and a lot are in French, Japanese and Urdu...but lately youube overwrites the original audio with a horrible ai voice in robot weird english. google only shows me solutions for desktop computers or using an app I don't have. Can you help please? Thank you70.67.193.176 (talk) 03:41, 19 July 2025 (UTC)[reply]

Does the browser allow extensions? YouTube No Translation promises to keep the original audio. This is the Firefox add-on but it says there's a Chrome version. Some years ago when I was choosing a mobile browser it was difficult to find one that supported extensions and I ended up with the obscure "Kiwi browser", not mentioned on Wikipedia even in the list of web browsers, but perhaps the situation has improved since then. (Ah, I see this add-on is for Firefox desktop, so this probably isn't the solution.)

It seems there is a gear icon for options which will restore the original soundtrack, but the option resets with every video. ... But again, not available on mobile for some (?) reason.

Another addon/extension which may possibly work on mobile Firefox/Chrome-based browsers: Youtube Anti-translate. It says "titles", but on the GitHub page, about recent versions it says "This long awaited update enables YouTube's translations to be removed from: automatically dubbed audio tracks of videos". Card Zero (talk) 04:55, 19 July 2025 (UTC)[reply]