Wikipedia:Reference desk/Archives/Computing/2012 January 26

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January 26

Where can I learn to build my own mobile apps?

As you can see on the comments here, 11-year-old Caleb claims that he makes Android & iPhone apps. He obviously didn't learn to in college.

Where would I learn to build them myself, and would it cost anything to learn to build apps? Thanks. --70.179.174.101 (talk) 04:21, 26 January 2012 (UTC)

iOS apps are written in Objective-C. There's probably a book about it somewhere out there. →Στc. 04:33, 26 January 2012 (UTC)

Do you already know how to design and develop software? If so, head straight to developer.apple.com/ios or developer.android.com to learn the specific toolchains on these popular platforms. I also liked developing mobile software for Java ME telephones and devices, though it's a technology that's somewhat fallen out of favor in recent years. If you are not already a software developer, you may find the mobile development enviroment somewhat challenging; there are a lot of complex systems to learn and a lot of terminology you are unfamiliar with. Furthermore, these platforms tend to require expensive hardware and software tools, if you intend to develop a well-designed and well-tested application. (Though, to be fair, it is possible to learn and develop with a very small budget, especially if you are an exceptional learner). Start by reading about software development in general, and seriously invest some time learning how to program computers. After you've developed a basic proficiency, select one or more platforms,and focus on learning the software toolchains and workflows for each system. Nimur (talk) 06:56, 26 January 2012 (UTC)

For a quick fix, go to your favorite Internet search engine and type in iphone programming tutorial. You'll find articles, videos, and books. Maybe start with a couple of video tutorials. Captain Hindsight (talk) 10:38, 27 January 2012 (UTC)

why is my sparkle nvidia geforce 210 512mb graphics card not working?

hello......... i brought a Sparkle nvidia geforce 210 512mb ddr3 graphics card. but whenever i plug it in my motherboard it is not detecting only...... i changed that graphic card and replaced it 3-4 times from the shop but the problem is same... ealier i was having windows xp and in that my graphic card was working but at that time my computer used to freeze and appear blue screen...... so i formatted and istalled windows 7... but now when i installed windows 7, my graphics card has become undetectable...

I did following things but the problem is same:-

1. i downloaded latest driver from nvidia's site
2. i replaced the graphics card 2-3 times as it is under the warranty period
3. i am also having INITIAL DISPLAY in the BIOS settings to PCI Express Card
4. i am also having enough power supply for the graphics card

BUT INSPITE OF DOING ALL THESE THINGS THE PROBLEM REMAINS THE SAME...

My Computer Specs are as under:-

Motherboard: Mercury Pi945GZD
Processor: Dual core
CPU: 3 GHZ
RAM: 3 GB
HDD: 160 GB
OS: Windows 7 Ultimate 32 bit
Power Supply: 300 watts

I did each and every thing possible to make my graphics card work.... but nothing changed

plzzzz plzzzzzz plzzzzz help me — Preceding unsigned comment added by 49.213.50.64 (talk) 06:52, 26 January 2012 (UTC)

It sounds as though you've already performed the standard set of hardware and software diagnostics. I would double-check that your power supply is in fact sufficient to power your entire system - as this is the most probable source of problems. Because you have already replaced the graphics card 2-3 times, it's unlikely that the cards were all faulty - but what about the motherboard? It's plausible that your system board has a defective PCIe interface. Have you tried using the card in another system/motherboard? Nimur (talk) 07:01, 26 January 2012 (UTC)

(I have also formatted your wikitext for better readability). Nimur (talk) 07:04, 26 January 2012 (UTC)

You have to be more precise. What do you mean by "undetectable"? Are you able to get past BIOS when you plug the monitor into that card? Can you boot into Windows? If you can get to Windows, what happens then? --Itinerant1 (talk) 08:39, 26 January 2012 (UTC)

Why is it that some people, who otherwise spell English well, like the OP here, insist on spelling the word "please" as "pls", "plz", or $DEITY forbid, "plzzzz"? Even our company's Director of Human Resources spells English otherwise almost perfectly correctly, but consistently spells "please" as "pls". JIP | Talk 20:19, 26 January 2012 (UTC)

I've started to see this as a sign of disrespect. When writing to someone who needs to be respected, most people can be relied upon to spell out words completely. This is especially true of 'please', which is somewhat of a placeholder in English - just there to fill the space in phrases like Please do this (meaning Do this). If someone abbreviates it to pls, they are showing that they don't really want to say please, they just require it to fill up the sentence. I imagine that the fact it's your HR Director that's doing this is not a coincidence. - Cucumber Mike (talk) 10:31, 27 January 2012 (UTC)

Information Technology Foundations

What are the basic objects that computers process? How do computers handle music and video? — Preceding unsigned comment added by Crexia (talk • contribs) 12:21, 26 January 2012 (UTC)

The term "computer" in modern usage almost always means a digital electronic device. Since it is a digital device, everything that it handles is captured as a set of discrete numbers or integers - and all modern computers use a binary representation to store these numbers. For an outline of how music and video can be turned into numbers, see our articles on digital music and digital video. Gandalf61 (talk) 15:28, 26 January 2012 (UTC)

By random chance, I came across an excellent book last night, by a famous computer researcher, Brian Kernighan. His new book, published in 2011, is called D is for Digital - What a well-informed person ought to know about computers and communications. I haven't yet had a chance to read it, but it seems to be geared towards informing the general public about how computers work. And, if it's like the author's previous book ("C", with similar book cover stylings), it's probably simple, informative, accurate, and thorough. According to reviews, it walks the average computer user through the technologies that make their day-to-day activities possible. Nimur (talk) 16:22, 26 January 2012 (UTC)

Making a New Word Doc from An Existing doc

How can I get, say, pages 59 to 72 as a separate document in itself? KägeTorä - (影虎) (TALK) 13:20, 26 January 2012 (UTC)

Maybe I am missing something here, but can't you just copy the document file or "Save As ..." to a different file name, then delete the pages you don't want ? If you want to preserve the original page numbering then the "Format Page Numbers" dialogue has a "Start at" option. Gandalf61 (talk) 13:47, 26 January 2012 (UTC)

Cheers, all done. This was for entering in memoQ. Thanks a lot. Sometimes simple is just too simple. KägeTorä - (影虎) (TALK) 14:18, 26 January 2012 (UTC)

drop-in code for a survey on my web page

Can you tell me where I can use an external complete solution like a linked image, but the site hosts a quick little survey for me. I use a pretty bad host, I think it barely has PHP support, and I certainly don't have root, so what would really help is just a line of HTML I can just drop in. --188.6.79.116 (talk) 15:13, 26 January 2012 (UTC)

The easiest option is to use Google Docs to create a form, and then use a small IFRAME to display it on the page. I've used this for surveys before; it's pretty easy. Go to Google Docs, go to Create, go to Form. After you've set up the form, go to "Embed" and it'll give you the one line of HTML to make it display. It saves the submitted data as a spreadsheet and doesn't let anybody other than you access it. --Mr.98 (talk) 17:31, 26 January 2012 (UTC)

So what happenswhen you divide by zero?

In a calculator, nowdays if you try to divide by zero it will cancel the operation and display that message.. What happens when you got a calculator that is not modified to stop the operation when the divisor is at 0? what the calculator is going to do? what it is going to display? --190.60.93.218 (talk) 19:53, 26 January 2012 (UTC)

Calculators aren't 'modified' to detect a division by zero, they are designed that way. If they were designed to do something else, they'd do that instead - but whatever it was, it wouldn't give a meaningful result. AndyTheGrump (talk) 20:04, 26 January 2012 (UTC)

...and we even have an article on division by zero, which goes into further details. AndyTheGrump (talk) 20:07, 26 January 2012 (UTC)

What type of calculator? This matters a lot. Even though calculators are very small, they have sophisticated microcomputers inside of them, and may be running arbitrarily-complex software. For example, a TI-89 has an operating system and a symbolic algebra system to interpret your input. It will very probably return the result "∞", depending on your mode and your input.

In IEEE-754, which is implemented in some newer and larger calculators (and most desktop computers), the result of a double-precision number divided by zero is positive or negative infinity, or NaN, depending on your input; and this is not considered an "error." The result of an integer division by zero is a processor exception or an ALU error flag on many computer types.

The ultimate point is, this behavior should be well-documented in the hardware or software specification for your calculator. If you're running a calculator that doesn't come with a manual (as many small desktop and pocket calculators), you may be able to research its inner-workings on the web by searching for its brand and model. Nimur (talk) 20:42, 26 January 2012 (UTC)

It seems that this is what you are looking for - Cucumber Mike (talk) 10:24, 27 January 2012 (UTC)

We have an article on division algorithms at Division (digital). I would imagine that all computers and calculators for a long time have been designed to check for a zero denominator before trying to carry out division, but what would happen if they didn't would depend on the algorithm being used. For example, you can see that in Newton-Raphson division, a denominator of zero would lead to the initial estimate being doubled at each step until Arithmetic overflow occurs. 130.88.73.65 (talk) 11:35, 27 January 2012 (UTC)

radical new-age solution

a good solution would be to just reduce everything except any divisions by zero, and display that as-is. In other words, the ansewr to (34+56)/0 would be displayed as 90/0 (in red to draw attention to the fact that it's NaN in the traditional, left-brained white male hegemony sense of the word, or with a note to that effect) and the user can decide for themselves existentially what that means for them. Probably a mistake typing the formula in. — Preceding unsigned comment added by 188.6.79.116 (talk) 17:12, 27 January 2012 (UTC)

What's (30/0)+20? --Stephan Schulz (talk) 17:21, 27 January 2012 (UTC)

This isn't really very "radical," either. Most computer algebra systems can perform such operations. For example, the simplify() command in Maple will perform such symbolic algebraic manipulations. It will try to reduce the expression to the simplest representation that is mathematically consistent (using a sophisticated algorithm). My TI-89's battery is currently discharged, but as soon as I get home and swap in some new ones, I'll let you know how TI-89 processes or evaluates such symbolic statements as "(34+56)/0" or "(30/0)+20". A quick glance at the TI-89/92 Guidebook has an entire chapter on Automatic Simplification for symbolic expressions. As I mentioned before, there are circumstances when a divide-by-zero will fail - for example, in the numeric algebraic equation-solver, which in some cases will not produce symbolic results - the result is Calculator Error Code 160. "For example, zeros(2x+3=0,x) is invalid because the first argument is an equation."[1]. Personally, I don't see what NaN has to do with left-brained white male hegemony. Every person I ever knew who worked on symbolic algebra algorithms was a female. Nimur (talk) 18:49, 27 January 2012 (UTC)

90/0 is +∞ in IEEE floating point, not NaN. Note that x/0 (with x a nonzero integer) reduces to 1/0 if you follow the usual rules for reducing fractions to lowest terms, so distinguishing 1/0 from 2/0 makes no more sense than distinguishing 1/2 from 2/4. 1/0 would be a reasonable representation of +∞ or signless infinity in an arbitrary precision rational number package. -- BenRG (talk) 18:50, 27 January 2012 (UTC)

Just for the record, the TI-89 and most of the other TI calculators do not use IEEE floating point. They use an 80 bit floating-point scheme. This is sufficient justification for me to call a Texas Instrument a "weird" computer. (Argh, TI has removed their `89 Software Developer documentation since the last time we talked about it, in 2010 If anyone finds the `89 hardware/software guide, please feel free to post the new link). Nimur (talk) 18:54, 27 January 2012 (UTC)

If you implemented a division algorithm in a straightforward fashion (not necessarily what the calulator actually does), and left out a check for that case, division by zero would probably run forever (probably it would perpetually shift the zero up, trying to find a non-zero digit in the right place). There is some sense in which this is a "natural" failure mode for certain calculations of undefined values: a boolean function like f(x)= not(f(x)) is "wrong" in the sense that any value it returned would need to satisfy y = not(y), which is impossible. But f doesn't return any value. In programming languages like ACL2 that treat programs as proofs, you're not allowed to define a function without also proving that it does terminate. In such a case, division has to be defined as a partial function -- you'd need to declare that division by zero is not valid in advance. Paul (Stansifer) 03:10, 28 January 2012 (UTC)

Paul thanks! a lot! (So what is the division algorithm of nowdays calculators?) 190.158.184.192 (talk) 04:55, 29 January 2012 (UTC) (PD:I'm OP)

I remember a mechanical calculator from the 1960s that would run indefintiely if you divided by zero. Bubba73 ^{You talkin' to me?} 01:58, 30 January 2012 (UTC)

I was told about these mechanical calculators, and I'm surprised that they do not mention that issue in the divide by zero article. It should be added to be honest.

137.81.118.126 (talk) 00:42, 1 February 2012 (UTC)