What percentage of game content is normally free on a Free-to-Play game?

Question: If I wanted to launch a free-to-play game with different characters, weapons, items and clothes that can be either unlocked through gameplay or bought with real money, what percentage of items should only be available for real money? This isn't "subjective" - I'm interested in examples of real games and estimates of what percentage of their content is free.
Comment: If I had to guess, I would say the percentage by count/size is 5-10% at most, but if you weight by "coolness", the percentage is 90-95%. But I don't have any numbers to back this up.
Comment: do you need further ideas or answers?  I know I didn't directly answer your question, because I think you needed to look at the problem a little differently.
Answer: The US Virtual Good market (freemium games qualify) is expected to hit 1.6 Billion dollars this year.
0.01% of that is still 100K.
You shouldn't concern yourself with percentage, per se, but with content.  Which items are paid for may be more important than how many.
My general rule is this, if an Item can save someone 5-10 minutes during game play, or advance to the next "level" automatically (like a +1 item) charge a buck.  Angry Birds uses this idea with the Mighty Eagle.
In all the zynga games I've played, it was either A) advertise for them by friending people, or B) pay money to advance past an hour of play.  I don't necessarily like this style, because it frustrates me and forces me to stop playing if I don't have the friends.
In my game (Shining Force style game) I'm making 'promotion' cost money.  You can still beat the game with a level 30 fighter, but a level 30 dragoon will be so much cooler.
Answer: Analysis
The problem with asking for a hard figure here, is that this is an extremely variable number.
On the one hand, you have something like World of Warcraft, which, while not exactly Free-to-Play, still might serve as an illustrative example on the one end of the spectrum, with approximately 0% of content that is only available for cash. (The Celestial Steed)
On the other side of the spectrum you have producers like Zynga (of FarmVille fame) who maintain a catalog that is, at a wild guesstimate, about 50-60% cash-only items, and a fair chunk of these items are additionally time-limited (e.g. Halloween stuff, Christmas stuff, etc.) (Note: For various reasons, these numbers are difficult or impossible to pin down to an exact number; but when browsing the store in a game like FarmVille or FrontierVille, it seems as if basically every other item is bought with for-cash currency.)
On the gripping hand, it might be interesting to mention the spectacularly successful game by EA, The Sims 3. If you discount the initial cost of the game, which is relatively low and a one-time expenditure; their model works a lot like a Free-to-Play game.
Another wild guesstimate on my part puts their for-cash catalog at about 50%; unless you count content from the expansions. (A fairly rough breakdown puts cash-only content at about 30% of their catalog; free content at about 30%, and an additional 40% in expansion pack content.) (Note: Again, these numbers are hard to pin down, as they aren't exactly published anywhere; but these rough estimates are based on observation of the EA store for TS3 content.)
And here's the real clever bit what they do: With each expansion they bump the version number, giving players a host of new gameplay features; if you don't buy the expansion, but keep the "free-to-play" version; you only get the framework, and not the content required to make the feature interesting.
Summary
How much pay-to-play content you can get away with is strongly related to how much the game costs to play. In a Free-to-play game, you can probably get away with as much as 60-70%; but a more optimal popularity/profit-scale is probably achieved from setting it at about 50%.
Additionally, as demonstrated by the WoW example above; the ratio is not as important as the price and relative coolness of the item. Even if you only have one cash-only item, if it's insanely awesome you can make an incredible amount of money from it, even if it's just cosmetic, so long as you have enough players. (Estimates put the Celestial Steed at about $2.5 million of income, at the very least.)
Summary of the summary

Make items that confer stat bonuses, power and glory attainable to all players, or you'll lose them as they realize your free-to-play game is actually free-to-play-pay-to-win.
Package your ball-shatteringly awesome cosmetic items with ho-hum or sub-par stats up and sell them to your large player base for a stiff but reasonable price.
????
Profit
Comment: If it's an extremely variable number, prove it with concrete examples, not guesses.
Comment: I made my response a comment, not an answer, because it was a guess. Also, I lead off and finished by saying I had no evidence.
Comment: @Joe Wreschnig: Kettle, meet pot. Consider the degree to which you substantiate your own comment, perhaps?
Comment: There are several free to play pay to win games out there doing well for themselves.
Comment: @Joe Wreschnig: And I'm presenting a number of takes on the issue; none of which are being presented as hard fact, but merely for your consideration. At no point am I claiming that my numbers are final; in fact; I'm claiming that they very much are not. I am, however, trying to present a *useful* answer, i.e. one that is not merely a long list of statistics. I'm sorry if that offends you.
Answer: I've recently locked most of my game; despite having really few users you might be interested.
There are 6 classes ("levels"), and non-paying users may only acquire class 0 or class 1 players and weapons. Also, they can't do direct trading with other users, but they are allowed to use the auction (still can buy only class 0 or class 1 stuff).
Moreover, I have set up an exclusive conference, that will be the "main" conference, only for paying users. Non-paying users can still play as much as they want in the "lesser" conference.
Answer: Well you'ed have to guess on it really since most of the games change there what the player can only buy with real money list, sorry best thing I could think of. Most of the games I've played with free-to-play usally keep around, and I'm guessing a bit, like 5-10 percent like  Joe Wreschnig said, but it is really up to how big it is. If it is like a small game, like im guessing yours would be at the beggining, they make almost everything avaible in-game but really hard to get like a very rare drop and might have a few items that you can only buy, but it gives you a big advantage.
Check games like holy-war, Shogon Kingdom, and maybe game company's like perfect world if you want to reasearch your self.


Can I buy Ether directly to Ledger Nano S?

Question: Is it possible to buy Ether directly to Ledger Nano S? Because I don't want to download Mist, then create account there, and then wait for the entire blockchain to sync, mainly because while syncing, Malwarebytes is going crazy blocking many outbound IPs! I hope that they're not there to steal my Ether! That's why I want to directly buy Ether to the Ledger, or that would not be possible?
Answer: Nope, got to go through the process like everyone else. You wouldn't want to accidentally get your ether stolen/siphoned off if you gave it a direct line to what should be a secure wallet.
Try this tutorial listed on their support page, its as direct as it can get while being secure.
https://ledger.zendesk.com/hc/en-us/articles/115005199489-How-to-buy-Ethereum


Travel to India with expired Indian passport?

Question: I am on H4 dependent and an Indian citizen,my passport has expired 2 months back,can I travel to India at this moment with expired passport?
Comment: I do not think it is very difficult to renew.. expired or not.. Maybe extra checks, but if all is ok, they can not deny him passport. But for sure he can not travel on expired passport, as Airline will not let him board.. Better to renew the passport before travelling.. The question is.. for all the time thapassport was expired, he was kind of passportless?
Comment: It is very difficult for an Indian citizen to renew an _expired_ passport _outside_ India. To avoid trouble you should renew your passport before it expires.
Comment: @Davinder what is the question? You have typed a statement with a wisdom mark.  He was without a valid passport; what aspect of that were youquestioning?
Comment: @phoog Sorry, I meant.. Was he/she passportless in this time? Is it not same as stateless? Is it allowed in H4 Visa? (I have no idea) because generally, Tourist Visa (Multiple, long term), are valid only with a valid passport. In any case, IMHO, OP need-to/should renew passport before travelling.
Comment: @Davinder a passport is evidence of citizenship.  It is not synonymous with citizenship.  Babies are generally born with one or more citizenships, but with zero passports.  I do not know the rules in the US for nonimmigrants.  I suppose they are supposed to renew before expiration, but I suspect that falling to do so is pretty much a minor problem of an administrative nature.
Answer: India may let you in if you get there. However, your biggest problem is that airlines will probably not let you board without a valid passport. And if you cannot board the flight, it is a moot question whether India will let you in. You should get an Indian passport or other travel document from an Indian consulate before you travel.
Comment: Airlines dont check for 6 month validity generally it is a visa stamping condition and not travel itself.  However the answer per se is right, no airline will allow you to board without valid papers
Comment: For India, Indian passports must be valid on arrival according to TIMATIC, nothing more nothing less
Comment: @ottodidakt It is not applicable for India. You need a passport that is valid on arrival in India.
Comment: Airlines usually check for at least six months of passport validity before they let you board. However, I have noticed that they sometimes let you board with less validitiy as long as you sign a letter indemnifying them of any consequent liability. Not sure if they'd settle for this in case of an expired passport but they just might if you are traveling to your home country.
Answer: Airline will deny you boarding with expired passport. Only thing you can do is go to nearest Indian embassy and renew the passport. It can take two weeks.
If it is urgent to travel, you can directly approach the consulate and they will provide an emergency document that is valid only for returning to India. Once you reach India, you can renew it by applying online and going to local passport office.
Comment: I confirm this is correct: for many countries, TIMATIC states their own passports can be expired, but not for India


Wi-Fi dongle not visible to Raspbian Jessie, not working with wicd-curses (Pi 2)

Question: I apologize for having to create another thread about this, but after about three hours of googling, none of the numerous threads about Wi-Fi issues seems to quite match up with my setup or symptoms.
Here's what's happening: I recently wiped and reinstalled NOOBs onto my Raspberry Pi 2 to take advantage of multiboot capabilities. Mostly I want to use Raspbian. I've got a TrendNet USB Wi-Fi dongle attached, and the other OS's (LibreElec) can use it just fine - it sees networks, connects to them, and transfers data like normal.
However, when I log into Raspbian, when I click on the Wi-Fi panel, it says "no wireless interface detected". Right clicking and trying to open network preferences gives me an error about permissions. I don't know the bash command to open up that particular panel, otherwise I'd try sudo-ing that.
The driver and firmware appear to be in place. I tried messing with various conf files with no luck. (I've since restored them to their defaults). I tried ifdown wlan0 and wlan0 ifup but I get a DHCP error, (no response after some time).
The most promising thing happened when I hooked it up to Ethernet, downloaded wicd-curses, and booted that up. Up popped an accurate list of available Wi-Fi networks. But it won't connect to the only one I have a password to. I'm quite sure I'm entering the correct password, and I've selected the correct encryption (WPA 1/2 passphrase) but the log file says bad_pass.
Any ideas what I should try next?
Answer: I was able to solve this by wiping and reinstalling raspbian. Which kind of sucks, but apparently if anything goes wrong during the installation of the OS (which it can, invisibly and for no apparent cause), the wifi support can easily and seriously break.  Reinstalling made everything work with zero customizations etc.


Can somebody provide me with the $price per GHps in mining since the old CPU days til present pre-orders?

Question: Can somebody provide me with the $price per GHps in mining since the old CPU days til present pre-orders?
I don't mean energy usage or price vs price of btc.. simply hardware costs relative to how fast they hash.
Answer: There isn't really a good way of measuring that in the early days. When CPU mining was actually doable, people would just use hardware they had. It didn't necessarily "cost" them anything. Even with GPU mining it's hard to estimate GH/s/$ because these weren't made for mining.
Answer: I think this is what you are looking for:
https://en.bitcoin.it/wiki/Mining_hardware_comparison
it gives a large list of CPU and GPU hardware. It does not give MHS/$ for CPUs, because it is tricky to calculate. But you could estimate the value.
Actual preorder GHS/$ you can find at the mining dashboard:
http://mining.thegenesisblock.com/
Comment: I'm more looking for a historical evolution of the cost to hash..


Toyota prado 2009 Diesel auto

Question: When I sit at the lights in gear I am getting a louder than normal vibration sound. If I go into neutral I loose it and goes back to normal diesel sound.
Comment: Welcome to Motor Vehicle Maintenance & Repair!
Answer: If the noise changes as you speed up/slow down, I'd suggest you have a bad motor mount. When these wear out, they tend to do exactly as you're suggesting which is make noise as you have it in gear. The engine torques over, connecting the engine to the frame and makes noise. When you put it in neutral, the engine goes back to a "resting" state and no more noise. As you speed up/slow down, the mount is continually connecting/disconnecting with the frame, so the noise comes and goes. You'll most probably experience it as you speed up. You may also hear a slight clunking sound as it shifts gears.

Toyota prado 2009 Diesel auto


$NP\subseteq TIME[O(n^{\log n})]$

Question: Is it more plausible that $NP\subseteq TIME[O(n^{\log n})]$ than $NP\subseteq P$? I don't see this mentioned much and is there a reason why? If this question doesn't make sense, explain why.
Comment: Notice that, for every $c$, $n^{\log n} > n^c$ eventually. (Actually, this happens exactly when $\log n > c$.) $n^{\log n}$ grows faster than any polynomial.
Answer: It is definitely more plausible, for the simple reason that $NP \subseteq TIME[O(n^{\log n})]$ is implied by $NP \subseteq P$. However, it is conjectured that $NP$ requires exponential time (this is known as the Exponential Time Hypothesis), and so both statements are conjectured to be false.

$NP\subseteq TIME[O(n^{\log n})]$


I can't extrude on the z axis

Question: I was trying to extrude the edges in the z axis using the extrude tool from the toolbar and not the shortcut key. The first time I extruded the edges it was fine. But the second time I tried to extrude the edges I couldn't do it in the z axis. It was allowing me only in the x axis. I was wondering what have I done wrong.
Comment: I got the same problem, just fix it by appling all transforms.
Answer: (Blender 2.92)
Wow. This is a curious one. I think this is what's going on..

You're extruding edges, along their median (actually mean) Normal, which is to say the mean normal of their vertices. In the first extrusion, all the vertex normals have a -Z component, the X's and Y's cancel, so the mean normal is -Z. In the second extrusion, none of the vertex normals has a Z component, the other components cancel, and so the Normal is 0. Blender seems to gives an arbitrary vector for this?
TL;DR
Fill the hole and  extrude a face, which has a normal, or use the XYZ setting for the tool.
The behaviour has changed in version 2.93
Comment: I don't see the problem. Maybe it's just incorrect use? I don't have to create a face.
Comment: @Gordon Thanks! This has been fixed in 293 .. I wonder how, though? .. i.e. how Blender decides what the mean normal of a collection of vertices is, when the vector sum is 0? I suspect it must be doing what this post suggests you do manually. Although, come to think of it, I don't know how blender defines the normal of an arbitrary ngon, either, reasonably economically. If I knew where to look.. :)
Comment: Oh yeah I see it changed, just tried it in 2.83.5, I've edited my answer to give a full explanation on how to work with the tool to achieve what he wants... still no need for a face, but you mention the XYZ setting already ;)  But I guess the answer that jmbenck gives is based on 2.93 and using it wrong - because in the old version, applying a transformation wouldn't help, he would still be facing the same problem that you explain in your answer: no Z component.
Answer: EDIT: As @RobinBetts pointed out, the behaviour changed in Blender 2.93 (see below), so here's what to do if you have an earlier version:
If you simply want to constrain the extrude to the global Z axis (not some custom orientation), you can simply switch the Extrude Region and Move tool from using the Normal to the XYZ axis with the button at the top. Or if you keep the Normal option, just grab the circle instead of the Plus. This let's you extrude freely without constraining the direction. If you now hit Z, the direction gets constrained to the Z axis just like it does when you're moving, rotating or scaling things.

And this is how it works in 2.93 and above: After the first extrude, you have the option to further move the extruded part by grabbing the arrow, or do another extrude by grabbing the plus.
First extrude:

Now if you want to move it further down without extrusion, use the arrow - if you hover over it, it becomes white:

But if you want to do another extrusion, hover your mouse over the Plus to grab it and it shows in white:

Just pull it down like you did the first time and you have another extrusion:

I can't extrude on the z axis


is evolution app available for android

Question: I was trying to find android evolution app (originally gnome personal manager application). The only result google gave me was the monkey->man evolution. Does anybody know whether somebody has ported evolution to android?
Comment: if you specify what exactly the features from Evolution that you want to have available from Android, I'm sure many would be able to suggest a replacement. The UI required in touchscreen environment is extremely different than the UI required in desktop applications, porting Evolution to android would essentially be creating a new app almost from scratch and there are many other calendar/email clients already available in Android.
Comment: well, apps like evernote are available in different platforms/devices. Before I start to use evolution I want to make sure it will be available also on mobile devices. If it's not, I'll probably stick to evernote.
Comment: Evolution is wholly a desktop software, it doesn't have a server-side component at all; Evolution only speaks in standardized protocols like POP/IMAP, Exchange, iCal, WebDAV, etc (before you ask, yes, there are Android apps capable of talking in these protocols). Evernote, on the other hand, is primarily a service. The nature of the two are *completely* different.
Comment: yep, Evernote offers a backend server, so that each client app can access the same data for an authenticated user. Ok, now I got the difference, thanks. Evolution is not what I need.
Answer: Never heard it was, and I'm pretty sure if it were I had heard. (Originally "Ximian Evolution", by the way ;) Neither have I heard of something comparable. Mail, Calendar, Todo etc. are available as separate apps, sometimes also in combinations, but then mostly only combinations of calendar + todo, not with mail.
Closest coming is probably Pocket Informant (USD 10), joining calendar, tasks, and contacts:

Pocket Informant 3 (source: Google Play; click image for larger variant)
I personally favour a combination of Business Calendar (bought the Pro), Business Tasks (integrates neatly into their calendar app), and K-9 Mail instead on my Android devices (and yes, on my Computer I use Evolution).

is evolution app available for android


How do I upgrade my Matter Manipulator?

Question: I've been playing Sarbound version 1.0 up until the first relic quest, I wan't to upgrade my MM (Matter Manipulator) but I must have skipped the tutorial which people say is how you unlock it. After looking through a couple of similar people's issues I've seen a bunch of people saying "activate the teleporter" or take the the flashlight out of the locker but nothing seems to work. Any one know how to fix this issue. (I also looked at S.A.I.L. and their's only the Dreadwing quests and Revisit the Erchius Mining Facility)
Comment: Your question is very confusing... are you asking how to start the tutorial quest, or how to upgrade your matter manipulator? Those are two very different answers.
Answer: I don't believe there is a tutorial on how to upgrade your matter manipulator. Information you find online is likely outdated, as the 1.0 release was only a couple of days ago.
To upgrade your matter manipulator, click on the "MM upgrade" button on the right:

In the window that pops up, select one of the available upgrades, and then press the UPGRADE button:

You'll need a certain number of Manipulator Modules to make an upgrade, which can be found in chests and reward bags.
Comment: Related note: I was playing for the first time in ages and had added the Frackin' Universe mod and the Quickbar mod.  This is buried in the Quickbar now, so if you can't find it and are using that mod, that's where it's hiding.  This answer helped me get there!
Answer: I believe the question that's being asked is how to unlock upgrades to the matter manipulator.  I'm assuming his screen is looking a lot like this, where there are enough manipulators, but no way to use them - they're still locked.
You have to select and upgrade the first tier.  That's the one with an icon in it.  Once that one is upgraded, then the next one will unlock.
Answer: In order to upgrade the matter manipulator you need to press on something that isn't greyed out- you can see the color on the water droplet, so if you click on it the upgrade button becomes yellow and you can update it. Having an expansion shot thats not locked doesn't mean that its an update you have.

How do I upgrade my Matter Manipulator?


Negotiation with hiring agency

Question: I am working on a college project where I set up a small company and need to hire 50 employees. Quotes I received from recruiting and hiring agencies are a bit too much for our budget. How can we negotiate?
Thanks.
Comment: How is it that a college project involves hiring 50 people?  That is a large number of people for a 1,000 person company to hire all at once-- the amount of time and energy to manage that many additional people let alone train them is not trivial.  You can, of course, advertise the positions yourself and put in the time and energy to recruit people rather than paying external companies to do that legwork on your behalf.  But the entire premise seems very odd.
Comment: I'm voting to close this question as off-topic because its about running a business not navigating the workplace as described in the [help]
Comment: Talk to your project advisor. Ask for some mentoring on the concept of "negotiation".
Comment: Is it a college project, and by that, I assume that it's a paper exercise, and not the creation of a real 50 employee company? If that's so, then you shouldn't be calling real agencies for quotes and negotiation; you'll be wasting their time. If it's a real company, it's unlikely that you'll need 50 trained professionals immediately - employ who you need, when you need them, based on your cashflow.
Answer: As you mentioned, this is a college project and not a real-life example. This means every single element should be challenged.

You do not have the budget. This part is straightforward. You can ask the agency if they can lower their price, the answer will most likely be no.
The agency is asking too much. As this is a college simulation in my understanding, there is a good chance that asking "can we change agencies?" will be met with "you can find the same service 5-10% lower with Agency XYZ".
We need to recruit 50 employees. Does it have to be 50 ? Wouldn't 45 or even 40 do the trick ? You only specified in the question that you need 50, but this should be challenged. In addition to that, 50 induces a threshold effect in several countries, so going from 49 to 50 employees can be extremely costly.
We need to recruit 50 employees. Do you need employees, or can you add some interns in the mix ? Their cost will be cheaper, but they can still realise most tasks.

Your entire project probably has more things which should be challenged, this answer only answered the elements you identified.
Answer: I think you are vastly underestimating the value that hiring through an agency can give to your organization.  They charge high fees because a lot of prospective placements actually fall through the cracks.   The recruiters' time isn't free, nor the account managers', nor the fancy office you expect to go visit them in, or the time of the custodian who cleans them.  Agencies have expenditures for phone, internet, advertising, and everything else you'd find in a service business.
Again, given that many like yourself will have an agency running like a chicken with its head cut off to fill a position, and THEN decide later that you don't really need the position filled -- how do you expect the agencies to stay afloat if you're trying to be cheap?  There's a point where they can't negotiate AND stay in business.
If cheap is your motivation, try Craigslist.  But you'll get what you pay for.
Answer:
How can we negotiate? Thanks.

First, you google for the word "negotiation" and you educate yourself as to what "negotiation" is and how the negotiation process works. Seriously.
Second, you say that you want to negotiate. WHAT do you have to offer? A negotiation is a trade. If you have nothing to offer, then you have nothing to trade. And if you have nothing to trade, then you have nothing to negotiate with. If you have nothing to negotiate with, then you are wasting everyone's time.
Recruiters usually ask for two months of an employee's salary. It's clear that you can't afford to pay two months of an employee's salary let alone 12 months of an employee's salary. Let's assume that you somehow managed to get the recruiters to work for free, how do you intend to pay your 50 employees? It doesn't look like you have thought things through.
Comment: The second paragraph is a bit bizarre.  In a negotiation over the price of services, of course you have something to offer: your business.  The negotiation is over what level of payment makes it worth their while to work with you.  You seem to be implying it's pointless to negotiate, but I don't see any rationale for that.  50 hires is quite a large volume of business and it's quite reasonable to expect the normal per-employee rate may go down because of that.
Comment: @dan1111 - The OP cannot afford to pay two months' of ONE employee's salary, which is the usual US fee for a successful recruitment exercise. You want to negotiate with WHAT available money again? You're making an "Alice in Wonderland" argument.
Comment: The only information I see the OP gave is that the quotes were "a bit too much".   Where do you see them saying that they can't cover the recruitment fee for a single employee?
Comment: @dan1111 - Take a hint: it's a college project. I am not even sure that the OP and his people can pay for anything with real money.
Comment: Admittedly the question is not really clear of what the scenario is.  But the assumption that they want to **really** hire a recruiter, yet have no real money, does not seem like the most likely scenario to me.
Comment: Don't be a pedant...He obviously wasn't asking in laymen's terms how to negotiate...

Negotiation with hiring agency


Content Delivery 2011 SP1 architecture understanding

Question: We are upgrading from Tridion 5.3 SP1 to Tridion 2011 SP1. We are done with Tridion Content Manager Server installation. We want to understand detail architecture on Content delivery server.

What is the difference between content delivery server and presentation server?
We have lot of Dynamic Component presentations as well as Embedded component presentations, exactly where we have to do changes in cd_storage_conf so that embedded presentations along with page will go in application folder (.net application) and Dynamic component presentations will go to SQL database? (in Tridion 5.3 there was a element in config file called "DefaultRootLocation"
While doing installation of Content Delivery we installed it on D:\Tridion.  After installation we can see subfolders like bin,cofig,incoming,lib, log, uninstaller etc. Our .Net application will be sitting on D:\inetpupp\.  Do we need to copy or change any folder, dll, config file to our .net application folder?
Where we can find some diagram, or architecture against which we can validate our installation?
Comment: What configuration do you currently have for #2? Don't put it in a comment please, just update the question with ***the relevant fragment***.
Comment: When you say configuration what exactly you are looking for ? Should I update on ,  section ?
Comment: I would also recommend a delta training so you can think better design choices.
Answer: What is the difference between Content Delivery server and presentation server?
Content Delivery is a set of modules from Tridion that you install on your presentation server. So we typically talk about Tridion Content Delivery and user145602's presentation server.
Do we need to copy or change any folder, dll, config file to our .net application folder?
Yes, you will indeed need to copy the relevant files (JARs, DLLs and _config.xml's) to your web site under c:\inetpub (or wherever you have pointed IIS to).
Exactly what to copy is documented extensively in the online documentation (log on required):
http://sdllivecontent.sdl.com/LiveContent/content/en-US/SDL_Tridion_2011_SPONE/task_DFE30215E62D42D097516F0450C853D7
Typically:

the DLLs go into the bin folder of your web site (unless noted otherwise)
the JARs go into a lib folder under the bin folder of your web site
the _config.xml files go into a config folder under the bin folder of your web site

Where we can find some diagram against which we can validate our installation?
The (online) documentation is full of architecture diagrams, such as this one (log on required): http://sdllivecontent.sdl.com/LiveContent/content/en-US/SDL_Tridion_2011_SPONE/concept_C72D061178C64B88A93134DE051A082C
But how directly applicable those are to your installation depends on many factors beyond anyone's control but you (or the people that set up and upgraded this system for you). If you want to validate your installation, I'd suggest getting an experienced consultant from SDL or one of our partners to walk through it with you.
Comment: Thanks Frank, that was quite informative.
What I also wanted to know was answer to point number 2 mentioned by user1453602.
Answer: I got this information regarding your query in point no. 2:
To enable storage of content on the local file system, ensure the
presence of the following  element, uncommented:
**<Storage Type="filesystem" Id="LocalFileSystem_01" defaultFilesystem="true" defaultStorage="true"
Class="com.tridion.storage.filesystem.FSDAOFactory">
<Root Path="STORAGE_PATH" />
</Storage>**

where STORAGE_PATH is the fully qualified path to the root folder of
your storage location.


How many Irrational numbers?

Question: How many irrational numbers can exist between two rational numbers ?
As there are infinite numbers between two rational numbers and also there are infinite rational numbers between two rational numbers. So number of irrational numbers between the numbers should be infinite or something finite which we cannot tell ? Or there exist some specific irrational which could be told by some methods ?
for eg. irrational numbers between 2 and 3 are 5^(1/2),7^(1/2) etc...
If there exists only some specific irrationals then why so?
Comment: The sum of a rational and an irrational is irrational. The number $\sqrt{2}/n$ is irrational for any positive integer $n$ and can be made as small as desired by choosing $n$ large enough.Therefore, given two rationals $r_1 < r_2$, the irrational number $r_1 + \sqrt{2}/n$ will be between $r_1$ and $r_2$ for all sufficiently large $n$. This shows that there are infinitely many irrationals between any two rationals. (In fact, a much stronger statement is true: there are uncountably many irrationals between any two rationals.)
Answer: There are uncountably infinite number of irrational numbers and countably infinite number of rational numbers.
Suppose we have a irrational numbers $q_0<q_1$ then we can construct a bijective mapping from $\mathbb R$ to $(q_0,q_1)$ that preserves rationality. This would show that the number of rational numbers and irrational numbers respectively in the interval is the same as the number of rational and irrational numbers overall.
We construct these by using a bijective mapping $\theta:\mathbb R\to(0,1)$ with the same properties and then use $f(x) = q_0 + (q_1-q_0)\theta(x)$. The mapping $\theta$ can be given as:
$$\theta(x) = \begin{cases}
{1\over 2-x} & \text{ if } x<0 \\
{1+x\over 2+x} & \text{ if } x\ge 0
\end{cases}$$
Answer: Let $r_1 < r_2$ be two rational numbers.  There are countably many rational numbers $q \in (r_1, r_2)$, and there are uncountably many $x \in (r_1,r_2)$.  So there are $uncountably$ many irrational numbers between any two rational numbers.
Answer: We know that the set of rationals, $\mathbb{Q}$ is dense in $\mathbb{R}$. Then, $\mathbb{Q} + i$ where $i$ is an irrational number (which is a subset of the set off all irrationals) is also dense in $\mathbb{R}$ (since $\mathbb{R}+i = \mathbb{R}$). Therefore, the set of irrationals is dense in $\mathbb{R}$ and there exists an irrational in every non-empty interval in $\mathbb{R}$. As there are infinite (unaccountably) such intervals, there are infinite irrationals between and two rational numbers.
Comment: Will there be a range of irrational numbers between two numbers or there will be some specific points for that ?
Answer: Let $r_1,r_2$ be rational numbers such that $r_1<r_2$. And let $i_1$ be an irrational number.
We can show that there is a irrational number $I_1$ in the form $I_1=r_1+i_1/k$ where $k$ is a non-zero real number such that $$r_1<r_1+i_1/k<r_2$$
Therefore,
$$r_1+i_1/k<r_2$$
$$k>\sqrt {(i_1 )}/(r_2-r_1 )$$
So, when,
$$k=⌊\sqrt{(i_1 )}/(r_2-r_1 )⌋+1$$
$$r_1<r_1+i_1/(⌊\sqrt {(i_1 )}/(r_2-r_1 )⌋+1)<r_2$$
There can be infinite number of irrational numbers satisfying this condition.
Comment: Please use MathJax to render the math. Thank you.

How many Irrational numbers?


What are the differences between struct and class in C++?

Question: This question was already asked in the context of C#/.Net.
Now I'd like to learn the differences between a struct and a class in C++. Please discuss the technical differences as well as reasons for choosing one or the other in OO design.
I'll start with an obvious difference:

If you don't specify public: or private:, members of a struct are public by default; members of a class are private by default.

I'm sure there are other differences to be found in the obscure corners of the C++ specification.
Comment: This [link](http://www.geeksforgeeks.org/g-fact-76/) summarizes the differences well.
Comment: Why people all use struct to build a tree then? Because it seems that the difference is not that much. BTW, [That](http://www.geeksforgeeks.org/) is a great website.@sjsam
Comment: Looking for the difference between `struct` in C and C++? [See here](https://www.geeksforgeeks.org/difference-c-structures-c-structures/).
Comment: @JW.ZG Not "all" people do! Those who do that either simply prefer to, or do not realise what `struct` means in C++. ;) But there's no reason you can't use the `class` keyword instead.
Answer: You forget the tricky 2nd difference between classes and structs.
Quoth the standard (§11.2.2 in C++98 through C++11):

In absence of an access-specifier
  for a base class, public is assumed
  when the derived class is declared
  struct and private is assumed when the class is declared class.

And just for completeness' sake, the more widely known difference between class and struct is defined in (11.2):

Member of a class defined with the
  keyword class are private by
  default. Members of a class defined
  with the keywords struct or union
  are public by default.

Additional difference: the keyword class can be used to declare template parameters, while the struct keyword cannot be so used.
Comment: Actually, the real _tricky_ difference between `struct` and `class` is that the latter can be used in place of a `typename` to declare a template parameter, while the former cannot. `:)`
Comment: That's not really a second difference, it's just that the question stated the difference incompletely.  All subobjects are private by default when using the `class`, public by default with `struct`, and both define a class type.
Comment: @MrUniverse: This is utterly wrong. (There's a school that uses this for a convention, but it's not syntactically enforced.)
Comment: I think you missed the point, Ben. It's the inheritance that's public for structs and private for classes. That's a very important distinction, and completely unrelated to actual member access. For example, the language could very well have defined it otherwise, e.g. both are publicly inherited by default, and you would get very different implications.
Comment: @sbi "the real tricky difference between struct and class" -- Cute, but the question is about the difference between *a* struct and *a* class, not about differences in where the keywords can be used.
Comment: @MrUniverse: You have created quite a confusion by mentioning typename. class is used as the word typename in template parameter, it is not the same word usage as class when you declare class or struct. template, class and struct cannot be mentioned in the same context that you have tried. typename is more correct word for what is meant with template. What is tricky is your way of trying to explain it.
Comment: @AssafLavie, are these really the only differences? I find that hard to believe without some history of the standard- why were classes AND structs both included in the standard, if the only difference is syntactic sugar?
This answer also lacks "reasons for choosing one or the other in OO design", a big part of the question.
Comment: @ariels `enum class` and `enum struct` were both introduced in C++11, and are [equivalent](https://stackoverflow.com/a/38536583/3529323).
Comment: @sbi To the best of my knowledge if you say `template` it will allow you to include any type but if you say `template` it will reject primitive types. I haven't checked this, but maybe it rejects a struct too.. don't think so though.
Comment: @Kuroineko I lol'ed but to be fair, _access-specifiers_ may modify the way the struct/class is accessed.
Comment: You're confusing "classes" (and "structs", which C++ does not have) with the keywords `class` and `struct`. Read http://stackoverflow.com/a/34907535/560648.
Comment: @sbi And don't forget that by using `class` instead of `typename` you can stop users from entering primitive types into a template.
Comment: Thanks, @bcsb1001. You are of correct! I must have been looking at an ancient draft. I can no longer find that wording at that section. I've removed my content entirely, it is now void.
Answer: Quoting The C++ FAQ,

[7.8] What's the difference between
the keywords struct and class?
The members and base classes of a
struct are public by default, while in
class, they default to private.  Note:
you should make your base classes
explicitly public, private, or
protected, rather than relying on the
defaults.
Struct and class are otherwise
functionally equivalent.
OK, enough of that squeaky clean
techno talk.  Emotionally, most
developers make a strong distinction
between a class and a struct.  A
struct simply feels like an open pile
of bits with very little in the way of
encapsulation or functionality.  A
class feels like a living and
responsible member of society with
intelligent services, a strong
encapsulation barrier, and a well
defined interface.  Since that's the
connotation most people already have,
you should probably use the struct
keyword if you have a class that has
very few methods and has public data
(such things do exist in well designed
systems!), but otherwise you should
probably use the class keyword.
Answer: It's worth remembering C++'s origins in, and compatibility with, C.
C has structs, it has no concept of encapsulation, so everything is public.
Being public by default is generally considered a bad idea when taking an object-oriented approach, so in making a form of C that is natively conducive to OOP (you can do OO in C, but it won't help you) which was the idea in C++ (originally "C With Classes"), it makes sense to make members private by default.
On the other hand, if Stroustrup had changed the semantics of struct so that its members were private by default, it would have broken compatibility (it is no longer as often true as the standards diverged, but all valid C programs were also valid C++ programs, which had a big effect on giving C++ a foothold).
So a new keyword, class was introduced to be exactly like a struct, but private by default.
If C++ had come from scratch, with no history, then it would probably have only one such keyword. It also probably wouldn't have made the impact it made.
In general, people will tend to use struct when they are doing something like how structs are used in C; public members, no constructor (as long as it isn't in a union, you can have constructors in structs, just like with classes, but people tend not to), no virtual methods, etc. Since languages are as much to communicate with people reading the code as to instruct machines (or else we'd stick with assembly and raw VM opcodes) it's a good idea to stick with that.
Comment: I disagree with "C has structs, it has no concept of encapsulation, so everything is public.", You can hide a definition of a `struct` inside a `*.c`-File and let other translations units only use it with a pointer. So you have a even stronger encapsulation, because other translations units do not even know what is inside the `struct`.
Comment: It's probably also worth noting that it was probably easier to have classes and structures work the same under the hood, than to have them be fundamentally different.  There might in retrospect have been some benefit to e.g. specifying that anything declared as a struct must be a PODS (i.e. forbidding structs from having virtual members, non-trivial default constructors or destructors, etc.) but such a thing has not to my knowledge ever been required by any C++ standard nor implementation.
Comment: @supercat the fact that it was an OO language in which a vast repertoire of programs written in a non-OO language were valid programs, brought the concept to the fore, and it does seem to come up more there than in more purely OO languages (and of course is actually defined in the standard). The history of early C++ definitely explains a lot about it. Stroustrup's "The Design and Evolution of C++" is an interesting read.
Comment: I perceive a religious war between people who feel that everything which isn't "oop-ish", should be, and those who think that OOP should be regarded as *a* tool, but not *the* tool. C++ certainly seems to embrace the latter philosophy, but I really don't know much about languages before it. My own philosophy is that when one wants an object one should use an object, and when one wants an aggregation of related but independent variables, one should use that. C++ makes no syntactic distinction between those kinds of things, and .NET tries to blur that distinction, but the little I know of D...
Comment: ...suggests that it recognizes it moreso than C++ or .NET.  Aggregations of variables aren't exactly OOPish, but that doesn't mean they shouldn't be employed when they're *useful*.
Comment: @supercat the sort of distinction between plain-old-data/other in itself comes from the experience of early C++ use, which of course needed early C++ to come first. The very first implementation was actually macros that re-wrote the `class` as `struct`, members as functions with the `this` pointer explicit, and so on. As such, it most certainly was easier to have them work the same way!
Comment: C++ was not the first object-oriented language, and I would doubt that it's the first to recognize PODS as a concept.  Your point that an early C++ front-end could largely ignore structures that existed within code at the same time as it created structures of its own certainly goes along way to explaining why C++ behaves as it does.
Comment: @12431234123412341234123: That's not stronger than C++, because C++ can (and often does) do the exact same thing.  "pimpl" is a common pattern.
Answer: Class' members are private by default. Struct's members are public by default. Besides that there are no other differences. Also see this question.
Comment: Not only members, but all access, including inheritance.
Comment: Well, I'd say the other difference is semantics.  Struct to many people makes them think "data structure" as a leftover from C.
Comment: @KrisKumler: Those are not "semantics"; they are personal feelings. Both `struct` and `class` declare a _class_ with identical semantics (notwithstanding parse-wise interpretation of the definition body).
Answer: According to Stroustrup in the C++ Programming Language:

Which style you use depends on circumstances and taste. I usually prefer to use struct for classes that have all data public. I think of such classes as "not quite proper types, just data structures."

Functionally, there is no difference other than the public / private
Comment: What difference? Please explain.
Answer:
Members of a class are private by default and members of struct are public by default.

For example program 1 fails in compilation and program 2 works fine.
// Program 1
#include <stdio.h>

class Test {
    int x; // x is private
};

int main()
{
  Test t;
  t.x = 20; // compiler error because x is private
  getchar();
  return 0;
}

// Program 2
#include <stdio.h>

struct Test {
    int x; // x is public
};

int main()
{
  Test t;
  t.x = 20; // works fine because x is public
  getchar();
  return 0;
}

When deriving a struct from a class/struct, default access-specifier for a base class/struct is public. And when deriving a class, default access specifier is private.

For example program 3 fails in compilation and program 4 works fine.
// Program 3
#include <stdio.h>

class Base {
public:
    int x;
};

class Derived : Base { }; // is equivalent to class Derived : private Base {}

int main()
{
  Derived d;
  d.x = 20; // compiler error because inheritance is private
  getchar();
  return 0;
}

// Program 4
#include <stdio.h>

class Base {
public:
    int x;
};

struct Derived : Base { }; // is equivalent to struct Derived : public Base {}

int main()
{
  Derived d;
  d.x = 20; // works fine because inheritance is public
  getchar();
  return 0;
}

Comment: I have removed code examples 3-7 as mentioned by experts
Answer: STRUCT is a type of Abstract Data Type that divides up a given chunk of memory according to the structure specification. Structs are particularly useful in file serialization/deserialization as the structure can often be written to the file verbatim. (i.e. Obtain a pointer to the struct, use the SIZE macro to compute the number of bytes to copy, then move the data in or out of the struct.)
Classes are a different type of abstract data type that attempt to ensure information hiding. Internally, there can be a variety of machinations, methods, temp variables, state variables. etc. that are all used to present a consistent API to any code which wishes to use the class.
In effect, structs are about data, classes are about code.
However, you do need to understand that these are merely abstractions. It's perfectly possible to create structs that look a lot like classes and classes that look a lot like structs. In fact, the earliest C++ compilers were merely pre-compilers that translates C++ code to C. Thus these abstractions are a benefit to logical thinking, not necessarily an asset to the computer itself.
Beyond the fact that each is a different type of abstraction, Classes provide solutions to the C code naming puzzle. Since you can't have more than one function exposed with the same name, developers used to follow a pattern of _(). e.g. mathlibextreme_max(). By grouping APIs into classes, similar functions (here we call them "methods") can be grouped together and protected from the naming of methods in other classes. This allows the programmer to organize his code better and increase code reuse.  In theory, at least.
Comment: It is not possible to create a struct in C++. It is only possible to create a class using the inherited `struct` keyword.
Comment: This is the most non-obvious thing about structs and classes.  "Structs are about data, classes are about code" can be rephrased as "structs are about data, classes are about data, security and operations performed on this data"
Comment: This answer doesn't seem to be about C++. In C++, `struct` declares classes (including `public`/`private`/`protected`, inheritance, etc).
Comment: How are structs abstract? Writing raw structs to a file is fraught with problems even in C (the usual problems include padding, endianness, different word size, etc). What is this `SIZE` macro you're talking about?
Answer: The only other difference is the default inheritance of classes and structs, which, unsurprisingly, is private and public respectively.
Answer: The difference between class and struct is a difference between keywords, not between data types. This two
struct foo : foo_base { int x;};
class bar : bar_base { int x; };

both define a class type. The difference of the keywords in this context is the different default access:

foo::x is public and foo_base is inherited publicly
bar::x is private and bar_base is inherited privately
Answer:
The members of a structure are public by default, the members of class are private by default.
Default inheritance for Structure from another structure or class is public.Default inheritance for class from another structure or class is private.

class A{
public:
    int i;
};

class A2:A{
};

struct A3:A{
};

struct abc{
    int i;
};

struct abc2:abc{
};

class abc3:abc{
};

int _tmain(int argc, _TCHAR* argv[])
{
    abc2 objabc;
    objabc.i = 10;

    A3 ob;
    ob.i = 10;

    //A2 obja; //privately inherited
    //obja.i = 10;

    //abc3 obss;
    //obss.i = 10;
}

This is on VS2005.
Comment: `_tmain` is not standard C++.
Answer:
Member of a class defined with the keyword class are private by default. Members of a class defined with the keywords struct (or union) are public by default.

In absence of an access-specifier for a base class, public is assumed when the derived class is declared struct and private is assumed when the class is declared class.

You can use template<class T> but not template<struct T>.

Note also that the C++ standard allows you to forward-declare a type as a struct, and then use class when declaring the type and vice-versa. Also, std::is_class<Y>::value is true for Y being a struct and a class, but is false for an enum class.
Comment: "You can declare an `enum class` but not an `enum struct`" is [incorrect](https://stackoverflow.com/a/38536583/3529323).
Comment: nice answer, though i am missing a clear unmistakable 0) the difference between `struct` and `class` in c++ is a difference between keywords, not between data types (or some better alternative ;)
Comment: @formerlyknownas_463035818: But don't you think `std::is_class::value` covers that?
Comment: yeah, just thought it could be more prominent, because thats the common misunderstanding and once thats out of the way the rest is just corollaries.
Comment: Nevermind, your answer is perfect as is, i wrote another one, doesnt hurt to have one more
Comment: @bcsb1001, Interesting; is that a C++20 thing or earlier? Pretty sure you can't in C++11, but always like to stand corrected.
Comment: @bcsb1001: It's always been that way. I wonder what I was smoking at the time. Thanks for pointing out.
Answer: Not in the specification, no. The main difference is in programmer expectations when they read your code in 2 years. structs are often assumed to be POD. Structs are also used in template metaprogramming when you're defining a type for purposes other than defining objects.
Answer: One other thing to note, if you updated a legacy app that had structs to use classes you might run into the following issue:
Old code has structs, code was cleaned up and these changed to classes.
A virtual function or two was then added to the new updated class.
When virtual functions are in classes then internally the compiler will add extra pointer to the class data to point to the functions.
How this would break old legacy code is if in the old code somewhere the struct was cleared using memfill to clear it all to zeros, this would stomp the extra pointer data as well.
Comment: Code that uses memfill to clear a struct probably has other offensive habits.  Go with caution.
Comment: @DavidThornley: Use of a zero-fill to erase or initialize a data structure is standard in C.  In a mixed-language project, one cannot expect the code in the C part to avoid `calloc` in favor of `new`.  All one can do is try to ensure that any structures used by the C part of the code are in fact PODS.
Answer: Another main difference is when it comes to Templates. As far as I know, you may use a class when you define a template but NOT a struct.
template<class T> // OK
template<struct T> // ERROR, struct not allowed here

Comment: If you have intended to emphasise that structures cannot be used as generalized types, then you a wrong. And `struct` is not allowed there just by convention (better say it's `class` keyword that is used in different sense here, see [Use 'class' or 'typename' for template parameters](http://stackoverflow.com/questions/213121)).
Comment: The keyword isn't allowed there, but you can pass in a class you defined with `struct` just fine. Simply try it. `struct T{}; template  void foo() {} foo();`
Answer: Here is a good explanation: http://carcino.gen.nz/tech/cpp/struct_vs_class.php

So, one more time: in C++, a struct is identical to a class except that the members of a struct have public visibility by default, but the members of a class have private visibility by default.
Answer: It's just a convention.  Structs can be created to hold simple data but later evolve time with the addition of member functions and constructors.  On the other hand it's unusual to see anything other than public: access in a struct.
Answer:
ISO IEC 14882-2003
9 Classes
§3
A structure is a class defined with
  the class-key struct; its members
  and base classes (clause 10) are
  public by default (clause 11).
Answer: The other answers have mentioned the private/public defaults, (but note that a struct is a class is a struct; they are not two different items, just two ways of defining the same item).
What might be interesting to note (particularly since the asker is likely to be using MSVC++ since he mentions "unmanaged" C++) is that Visual C++ complains under certain circumstances if a class is declared with class and then defined with struct (or possibly the other way round), although the standard says that is perfectly legal.
Comment: I know it's a very late comment, but be aware that the aforementioned warning is not without merit as the Windows ABI mangles structs and classes differently and therefore mixing (forward) declarations of class and struct can actually lead to hard to comprehend linking problems!
Answer:
. In classes all the members by default are private but in  structure
members are public by default.

There is no term like constructor and destructor for  structs, but for class compiler creates default if you  don't provide.
Sizeof empty structure is 0 Bytes wer as Sizeof empty class is 1 Byte  The struct default access type is public. A struct should
typically be used for grouping data.

The class default access type is private, and the default mode for
inheritance is private. A class should be used for grouping data and
methods that operate on that data.
In short, the convention is to use struct when the purpose is to
group data, and use classes when we require data abstraction and,
perhaps inheritance.
In C++ structures and classes are passed by value, unless explicitly
de-referenced. In other languages classes and structures may have
distinct semantics - ie. objects (instances of classes) may be passed
by reference and structures may be passed by value. Note: There are
comments associated with this question. See the discussion page to
add to the conversation.
Comment: "2. Sizeof empty structure is 0 Bytes wer as Sizeof empty class is 1 Byte". False. I just tested with `g++`. You might be thinking of Empty Base Optimization, but that applies to both too.
Comment: Not true. In C++ the size of an empty struct is 1. In C an empty struct is not allowed. GCC allows empty structs in C as a compiler extension and such a struct has size 0.
Comment: This answer is wrong. In addition to the size thing, the constructor/destructor part is also inaccurate: structs can have constructors and destructors just fine. In fact, `struct` creates full-fledged classes in C++.
Answer: While implied by other answers, it's not explicitly mentioned - that structs are C compatible, depending on usage; classes are not.
This means if you're writing a header that you want to be C compatible then you've no option other than struct (which in the C world can't have functions; but can have function pointers).
Answer: There exists also unwritten rule that tells:
If data members of class have no association with itself, use struct.
If value of data member depends on another value of data member, use class.
f.e
class Time
{
    int minutes;
    int seconds;
}

struct Sizes
{
    int length;
    int width;
};

Answer: You might consider this for guidelines on when to go for struct or class, https://msdn.microsoft.com/en-us/library/ms229017%28v=vs.110%29.aspx .

√ CONSIDER defining a struct instead of a class if instances of the
type are small and commonly short-lived or are commonly embedded in
other objects.
X AVOID defining a struct unless the type has all of
the following characteristics:
It logically represents a single value,
similar to primitive types (int, double, etc.).
It has an instance
size under 16 bytes.
It is immutable.
It will not have to be boxed
frequently.
Comment: That's about .NET/C#, not C++.
Answer: The difference between struct and class keywords in C++ is that, when there is no specific specifier on particular composite data type then by default struct or union is the public keywords that merely considers data hiding but class is the private keyword that considers the hiding of program codes or data. Always some programmers use struct for data and class for code sake. For more information contact other sources.
Comment: OP already mentioned that `struct` members are public by default, and the accepted answer from 2009 mentions inheritance. Why write another answer that adds no new information 4 years later?
Answer: Out of all these factors,it can be concluded that concept Class is highly suitable to represent real world objects rather than "Structures".Largely because OOP concepts used in class are highly practical in explaining real world scenarios therefore easier to merge them to reality.For an example,default inheritance is public for structs but if we apply this rule for real world,it's ridiculous.But in a class default inheritance is private which is more realistic.
Anyways,what i need to justify is Class is a much broader,real world applicable concept whereas Structure is a primitive Concept with poor internal organization(Eventhough struct follows OOP concepts,they have a poor meaning)
Comment: How is private inheritance "more realistic"? Most programming languages don't even have the concept of private inheritance.
Answer: The main difference between structure and class keyword in oops is that, no public and private member declaration present in structure.and the data member and member function can be defined as public, private as well as protected.
Comment: This answer doesn't seem to be about C++. In C++, `struct` declares classes (including `public`/`private`/`protected`, inheritance, etc).
Answer: The main difference between struct and class is that in struct you can only declare data variables of different data types while in class you can declare data variables,member functions and thus you can manipulate data variables through functions.
-> another handy thing that i find in class vs struct is that while implementing files in a program if you want to make some operations of a struct again and again on every new set of operations you need to make a separate function and you need to pass object of struct after reading it from the file so as to make some operations on it .
   while in class if you make a function that does some operations on the data needed everytime..its easy you just have to read object from file and call the function..
But it depennds on the programmer which way he/she finds suitable...according to me i prefer class everytime just because it supports OOPs and thats the reason it is implemented in almost every languages and its the wonderful feature of all time programming ;-)
And yeah the most unforgotten difference i forgot to mention is that class supports data hiding and also supports operations that are performed on built in data types while struct doesnt !
Comment: In C++ `struct` can have member functions
Comment: @chtz Thanks... i got to know about this feature just now.. thanks a lot.. i m just  a beginer not as expert as you so in future also need advices from u guys :-)
Comment: and actually, _member function_ is to be intended in its wider meaning. `struct` can have constructors, member function and distructor (possibly virtual, possibly private, protected or public). They can inherit and be inherited. so actually... everything a class can have. a tipical convention is to declare with struct what you would have declared as struct in C, and as class if we declare private and protected variable, virtual functions, ctor and dtor, and so on. But it's just a convention, not enforced by the language
Answer: I found an other difference. if you do not define a constructor in a class, the compiler will define one. but in a struct if you do not define a constructor, the compiler do not define a constructor too. so in some cases that we really do not need a constructor, struct is a better choice (performance tip).
and sorry for my bad English.
Comment: This is not true. There is no difference between a class defined with the `struct` keyword and a class defined with the `class` keyword in this respect.
Comment: @Ali No you don't.
Comment: when i use a struct with out a constructor, i get a better speed than a class with out a constructor.
Answer: Classes are Reference types and Structures are Values types.
When I say Classes are reference types,
basically they will contain the address of an instance variables.
For example:
Class MyClass
{
    Public Int DataMember;  //By default, accessibility of class data members
                            //will be private. So I am making it as Public which
                            //can be accessed outside of the class.
}

In main method,
I can create an instance of this class using new operator that allocates memory for this class
and stores the base address of that into MyClass type variable(_myClassObject2).
Static Public void Main (string[] arg)
{
    MyClass _myClassObject1 = new MyClass();
    _myClassObject1.DataMember = 10;

    MyClass _myClassObject2 = _myClassObject1;
    _myClassObject2.DataMember=20;
}

In the above program,
    MyClass _myClassObject2 = _myClassObject1;
instruction indicates that both variables of type MyClass

myClassObject1
myClassObject2

and  will point to the same memory location.
It basically assigns the same memory location into another variable of same type.
So if any changes that we make in any one of the objects type MyClass will have an effect on another
since both are pointing to the same memory location.
"_myClassObject1.DataMember = 10;" at this line both the object's data members will contain the value of 10.
"_myClassObject2.DataMember = 20;" at this line both the object's data member will contains the value of 20.
Eventually, we are accessing datamembers of an object through pointers.
Unlike classes, structures are value types.
For example:
Structure MyStructure
{
    Public Int DataMember;  //By default, accessibility of Structure data
                            //members will be private. So I am making it as
                            //Public which can be accessed out side of the structure.
}

Static Public void Main (string[] arg)
{
    MyStructure _myStructObject1 = new MyStructure();
    _myStructObject1.DataMember = 10;

    MyStructure _myStructObject2 = _myStructObject1;
    _myStructObject2.DataMember = 20;
}

In the above program,
instantiating the object of MyStructure type using new operator and
storing address into _myStructObject variable of type MyStructure and
assigning value 10 to data member of the structure using "_myStructObject1.DataMember = 10".
In the next line,
I am declaring another variable _myStructObject2 of type MyStructure and assigning _myStructObject1 into that.
Here .NET C# compiler creates another copy of _myStructureObject1 object and
assigns that memory location into MyStructure variable _myStructObject2.
So whatever change we make on _myStructObject1 will never have an effect on another variable _myStructObject2 of type MyStructrue.
That's why we are saying Structures are value types.
So the immediate Base class for class is Object and immediate Base class for Structure is ValueType which inherits from Object.
Classes will support an Inheritance whereas Structures won't.
How are we saying that?
And what is the reason behind that?
The answer is Classes.
It can be abstract, sealed, static, and partial and can't be Private, Protected and protected internal.
Comment: I think this is trying to answer the question for c#?  The question is about c++, and that makes this answer inaccurate, right?
Comment: This answer is complete nonsense. It uses a strange mix of Visual Basic and C# for its code examples, and the whole "Classes are Reference types and Structures are Values types"... thing only applies to .NET (ie C#) not to C++. You're in the wrong room, dude. This is where you belong : http://stackoverflow.com/questions/13049
Comment: @smw absolutely, he has written his sample code in C# and I came here to check that there wasn't a difference in parameter passing between C++ `struct` and `class`. No one here has mentioned it, nor the entire web. So I don't think this applies to C++ either.
Comment: This isn't even valid C# code - the keywords are all wrong.  "Public", "Static", "Int", and "Class" should not be capitalized and it should be "struct" not "Structure".  Description is mostly accurate for C# (though structs can still inherit interfaces, just not other structs), but doesn't answer the question since it was about C++...
Comment: But [this answer](http://stackoverflow.com/a/9127315/3423324) indicates the same is valid for C(++), that structs are used like value types. `int a = 3; int b = a;` and similar `MyStruct a=MyStruct("data");  MyStruct b = a;`
Comment: @luckydonald That also works for classes: `std::vector a {1, 2, 3}; std::vector b = a;`.
Answer: There are 3 basic difference between structure and class
1St- memory are reserved for structure in stack memory (which is near to programming language )whether for class in stack memory  are reserved for only reffrence and actual memory are reserved in heap memory.
2Nd - By default structure treat as a public whether class treat as a private .
3Rd- can't re -use code in structure but in class we can re-use same code in many time called inhertence
Comment: C++ structures do support inheritance and abstract methods.

Structure and class are allocated the same way. Allocating class on the heap even if they are not instantiated with a "new" doesn't make sense for embedded systems.
Comment: #1 is also wrong. The stack is used when you declare something of that type as a local variable, and the heap is used when you use the "new" operator.


Setting a watch function using kazoo when calling Zookeeper from a Flask application deployed using gunicorn

Question: I have a Flask application deployed using gunicorn. I'd like to integrate the application with a Zookeeper ensemble using kazoo, as the app relies on having up to date data from a get_children() call on one of the Znodes.
One option is for me to have the application fetch the data every time before it uses the data. The data don't change that often, so this is inefficient. Instead of polling Zookeeper, I'd like to call get_children() with a watch function when the app starts up, to have that watch function called back when there's a change in the data.
My question is, where do I set up this watch function effectively to ensure it will be called while the app is running? Should I set it up in the main file of the application (the file that's passed to the gunicorn command)? I guess I'm confused as to which thread will run the watch function while the app is running within gunicorn.
Answer: I found the answer to this upon further research. The kazoo library allows for passing a handler object when creating a KazooClient object. The default handler is SequentialThreadingHandler, which will run watch functions in a thread that kazoo creates separately from the main thread.
The SequentialThreadingHandler works in my Flask + gunicorn setting. Each gunicorn worker process will create a separate thread for watch functions when this handler is used.


Brussel Sprout Seedlings Hardy?

Question: I got my Brussel sprouts started early. They are in the ground (zone 5), but I think we are getting one more 30 degree frost on Friday. They are small little seedlings right now. My question is, can they stand a frost even in the seedling stage or do I need to doctor them to make sure they don't die? Also, they are very dark green in color and are quite small despite getting good sun. Do you think there might be a pH problem? I believe my soil is a little basic so I tried watering them with diluted vinegar a week ago. Any pointers here are appreciated.
Answer: I would have thought watering them with vinegar would do them more harm than a light overnight frost. Acetic acid is used as a herbicide and as a moss and algae killer. It is unlikely to make any permanent change to soil pH.
Brassicas are "cold climate" plants (they prefer temperatures below 70F/21C and usually "bolt" if the temperature reaches 80F/27C) and mature plants are frost hardy down to at least 20F. Sprouts can be buried under three feet of snow in winter for weeks, with no ill effects. The distinctive flavour of sprouts is actually a natural antifreeze compound.
Comment: Thanks for the info on the acetic acid. I got bad advice it looks like.

That said, your response did not address the main focus of the question which was are brussel sprout **seedlings** hardy.

Brussel Sprout Seedlings Hardy?


Weird value of track width with calculator

Question: I am currently working on a design where the power input will be connected to battery of car. I have a series of LDo and DC-Dc but the entry point is 9-36v and I am unsure what the current can be . I read here and there on the internet that car batteries can deliver until 40A.
Considering this I have checked with track width calculator but the result looks conpletely wrong (I find 111mm around).
What's wrong there ? What I am missing ? What should the be track width for car battery ?
Comment: Design should be driven not by the battery but by an awareness of the power your circuit is intended to draw under normal conditions, and the power it could draw under fault conditions until some protection device trips (using PCB traces as fuses is usually a design flaw rather than an intentional feature)
Comment: If the "protection device" opens, how much current will flow through the the power input connector?  Trying to design a circuit board without a better understanding of circuitry is a bit like trying to run before learning to walk.  If your assignment is only to physically implement a circuit electrically designed by someone else and to do so without you first fully understanding it, ask them to calculate the current.  And make sure they review and approve your work before it goes to the fab.
Comment: You never want to try to put that much current through a trace.
Comment: We have a protection device in the circuit, we use LM74610QDGKRQ1, but before this we still need to have some track between connector and this device.
Comment: The maximum current totalalling all the devices will be around 3A
Answer: First of all as already commented to your question, you don't design a circuit according to what the power supply can deliver, but to what the circuit in design will draw as an absolute maximum (plus some safety margin).
What I usually do, is to write a comment to each section of the schematic with the estimated current consumption.
Add them up and you know your complete current consumption.
Even if you are for some parts of your circuit not completely aware about the current requirements you can usually find some information in the datahsheet, estimate or simulated (by something like LTSPice for example).
On top of that you want to add some safety and you have your maximum current your complete circuit will draw.
With this information you can either use a lookup table or one of the plenty trace with calculators around (e.g. http://www.circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/) and you get your minimum trace with.
If space is not absolutely critical usually your PCB design software uses some default trace widths, select the next higher one to the calculated one an you are good to go.
Besides that various methods exist to increas the current capabilities of tracks, such as

using thicker copper (2oz instead of 1oz thickness for example)
add a wire connection
keep the solder mask of the high current tracks open and thicken the tracks by solder.


Using a SVM to classify audio data

Question: If I had 1000 audio files where three people are independently saying an animal at the same time, there can be 9 independent labels of animals. What features should I select from the audio file, and how should I normalize them to build the most accurate SVM to classify the audio files? For reference, I am doing this project in Python,so specific code examples and libraries would be very helpful. Thanks! -Joe
Comment: Why would you use an SVM for this (in 2023)? Sounds a bit like a school project.
Answer:
there can be 9 independent labels of animals.

One assumes the three speakers are making uniform draws
from {opossum, anteater, roadrunner} or some similar
urn.
In this case counting syllables (3) would be uninformative,
but for a different vocabulary we may see different results.
Simple techniques can isolate those three animals from one another.
For a less constrained input vocabulary, 50 ms or 20 ms
MFCC
windows would be a pretty typical feature to train on.
Find a pre-trained model
to tweak, or train from scratch.

Using a SVM to classify audio data


Why did Gauss think the reciprocity law so important in number theory?

Question: Gauss's Disquitiones Arithmeticae centers around the quadratic reciprocity law.
It seems that he developed the genus theory of integral binary quadratic forms to find a natural proof of the quadratic reciprocity law.
He later wrote 5 papers on number theory.
All of them are about the quadratic and biquadratic reciprocity laws.
Why did Gauss think the reciprocity law so important in number theory?
Comment: Quadratic forms are the primary focus, Reciprocity more a powerful tool.
Comment: @AndréNicolas Gauss proved the quadratic reciprocity using the theory of quadratic forms.
Other than this, if he thought the quadratic reciprocity more of a tool, it is hard to explain why he provided 7 different proofs of the reciprocity throughout his life.
Comment: Quadratic forms had a long history by then, and reciprocity had been spotted much earlier as relevant by Euler and Legendre.
Comment: @AndréNicolas If my memory is correct, Gauss developed the theory of quadratic forms independently from other mathematicians.
The same for the quadratic reciprocity.
Answer: It's the first non-trivial result in elementary number theory, and to find out whether a second-degree equation has a solution modulo some number, basically comes down to knowing quadratic reciprocity. The Disquisitiones starts with the basic definition of congruences, then solutions of first-degree congruence equations, and then second-degree, where one naturally bumps up against this problem.
Here is from the book itself:

Since almost everything that can be said about quadratic residues
  depends on this theorem, the term fundamental theorem which we will
  use from now on should be acceptable.

Later on he speaks of how Euler and Legendre came close to finding a proof, but despite their best efforts, could not. Clearly it was also a matter of pride for him.
Given how much of modern number theory revolves around generalizations of quadratic reciprocity, such as Artin reciprocity and the reciprocity conjecture of Langlands, it's easy to consider Gauss's intuition as justified.
Comment: The fantastic book 'Reciprocity Laws: from Euler to Eisenstein' by F. Lemmermeyer has the history as well as the math in great detail.
Comment: I corrected a typo that said Lagrange instead of Legendre. Gauss specifically refers to Legendre's "Recherches d'analyse indétérminée" Hist. Acad. Paris, 1785, p.465 ff
Comment: Thanks. Please notice that by the reciprocity law I mean not only the quadratic reciprocity law but also higher reciprocity law. Gauss clearly thought higher reciprocity law also very important.
Comment: The higher reciprocity laws were at first attempts to generalize quadratic reciprocity. Naturally, if you know how to solve quadratic congruence equations, next you want to solve cubics, hence cubic reciprocity, biquadratic, etc. The most general reciprocity law (Artin's) did not appear until a hundred years later, so it makes sense that Gauss would not be satisfied so soon.


How to keep my scroll out of my stand partner's face

Question: I'm playing on the outside of my desk, and my scroll is constantly in my stand partner's face. To have my violin off to the side seems kind of necessary for me to keep good posture, but this clearly isn't working. How can I modify my posture to keep my scroll more forward than to the side? Or whatever else needs to happen to address this problem.
Answer: The answer should be pretty obvious:  take a look at all the other violinists. How are their torsos oriented, and at what angle to their chests are they holding their violins?  If you are holding yours at an extreme angle compared with the rest of them, then you probably should be evaluated by your teacher or other advanced violinist.    And if it really turns out for musculo-skeletal reasons that you have to hold it that wide (which is unlikely!), you'll have to consider rotating your body away from your stand partner.
Now, with that said,  why not just swap inner/outer chairs?  Seems like a no-brainer from here.
Comment: Thank you. It would be a no-brainer to switch except that seating is assigned, and given the fact that I may very well be put in this situation again, it makes sense for me to trouble-shoot this.
Answer: Does this picture show your configuration?  With you sitting where the woman is?

If so, I have two suggestions.  (Caveat: I'm a cellist, not a violinist.  But I have been Suzuki coach for my two violist children.)  Swivel your body a bit to the right, and think in terms of pointing your scroll at the stand.  I'm having trouble finding a picture to illustrate this idea.  Here's the best I've come up with.

The woman in the green skirt has her knees pointed slightly to her right.  I actually think you could point your torso and knees a bit more to the right than that.  More like the woman farther back, with short white hair.  When you're practicing at home, you could work on getting used to pointing your scroll towards the music stand.  If you're reasonably tall, you may want to put your stand on top of a few stacked encyclopedia books so you can still see the music well.
Second suggestion: Cellists need more elbow room than violinists when sitting in orchestra.  So, from years of experience in getting the elbow room I need, to play comfortably in orchestra, here are my thoughts.  You can do some negotiating with stand partner and other neighbors, but personally I also check and adjust the chair set-up when I come into the hall or the rehearsal room, before unpacking my instrument, greeting people, checking bowings, etc.  I find it easier that way.
Because of the wedge shape of your section, you can often get a bit more space by moving your chair, your stand mate's chair, and the chairs behind you, back half a foot or a foot.
If you think about it -- is there any particular reason why violinists have to be packed like sardines?  If your ensemble is too big for your stage, then yes, but most of the time, I don't think so!


Lose weight at home?

Question: I have a question that's been runnin round my mind for a while now..... I don't have access to a gym, so I decided about doing body weight exercise but I don't know which ones to do!?! I'm not fat but I'm no skinny either, I have a little bit of lower belly fat and I can see a little bit of my lower ab, should I do cardio before body weights? Or should I not do cardio at all?
Answer: There is no definitive answer to the question of which order you should do these things in.
As for whether or not you should do cardio; yes, you should.
But keep in mind, if you want to lose weight, you're better of adjusting your diet first, and exercise second. Exercising does NOT compensate for an untidy and lazy diet.

Lose weight at home?


Best way to use a property to reference a Key-Value pair in a dictionary

Question: This is a fairly trivial matter, but I'm curious to hear people's opinions on it.
If I have a Dictionary which I'm access through properties, which of these formats would you prefer for the property?
///
/// This class's FirstProperty property
///
[DefaultValue("myValue")]
public string FirstProperty {
    get {
        return Dictionary["myKey"];
    }
    set {
        Dictionary["myKey"] = value;
    }

This is probably the typical way of doing it. It's fairly efficient, easy to understand, etc. The only disadvantage is with a longer or more complex key it would be possible to misspell it or change only one instance or something, leading me to this:
///
/// This class's SecondProperty property
///
[DefaultValue("myValue")]
private const string DICT_MYKEY = "myKey"
public string SecondProperty {
    get {
        return Dictionary[DICT_MYKEY];
    }
    set {
        Dictionary[DICT_MYKEY] = value;
    }

Which is marginally more complicated, but seems to offer additional safety, and is closer to what I would think of as the "Code Complete" solution. The downside is that when you also have a ///  block and a [DefaultValue()] block above the property already, it starts getting a bit crowded up there.
So which do you like better, and why? Does anybody have any better ideas?
Answer: I like the second one purely because any avoidance of magic strings/numbers in code is a good thing.  IMO if you need to reference a number or string literal in code more than once, it should be a constant.  In most cases even if it's only used once it should be in a constant
Answer: I agree with @Glenn for a purely nit-picky point of view.   The answer is whatever works for you.  All this code takes place in 10 lines (if you include the omitted last curly brace).  Nobody is going to get lost and the chance of mistyping is pretty slim (not impossible but very slim).  On the other hand, if you used the key somewhere else, then DEFINATELY go with the constant.
Personally, I would go off on you about your curly brace style. :)  Just kidding!  It really is a matter of style.
Answer: This isn't answering your question, but I don't think "DefaultValue" means what you think it means. It doesn't set a default value for your property.
See MSDN and this question for more details.
Answer: A lot of people would probably argue that the second option is "correct", because any value used more than once should be refactored into a constant. I would most likely use the first option. You have already gotten close to the "Code Complete" solution by encapsulating the dictionary entry in a strong typed property. This reduces the chance of screwing up retrieving the wrong Dictionary entry in your implementation.
There are only 2 places where you could mess up typing "myKey", in the getter and setter, and this would be very easy to spot.
The second option would just get too messy.
Answer: You could match the property names up to the keys and use reflection to get the name for the lookup.
public string FirstProperty {
get {
    return Dictionary[PropertyName()];
}
set {
    Dictionary[PropertyName()] = value;
}

private string PropertyName()
{
    return new StackFrame(1).GetMethod().Name.Substring(4);
}

This has the added benefit of making all your property implementation identical, so you could set them up in visual studio as code snippets if you want.
Answer: When you only use a magic string in one context, like you do, I think it's alright.
But if you ever need to use the key in another part of the class, go const.
Answer: @Joel you don't want to count on StackFrame.  In-lining can ruin your day when you least expect it.
But to the question: Either way doesn't really matter a whole lot.


Adolescent basketball strength training

Question: I am a 13-year-old boy who would like to improve his basketball performance using strength training. I am 5' 5" and 110 lbs. What are some exercises or workouts I can do safely to improve my biceps, triceps, quads, calves, or other muscles used in basketball?
Comment: @rrirower No, this should be asked *only* on Physical Fitness; Stack Exchange explicitly discourages cross-posting the same question to more than one site.
Comment: You should also ask this on the [fitness site](http://fitness.stackexchange.com/).
Answer: You should look at using some body weight exercises like:

push-ups - will develop different upper body muscles depending on width/direction of your hands on the floor
squats - will develop thigh/glutes strength for jumping
calf raises - will develop your calf muscles
Playdoh - Might seem like an odd suggestion but manipulating playdoh will help build wrist/forearm strength

In addition to strength training, you should also look at plyometrics for improving quickness. Exercises like box/squat jumps will help utilising the strength you have developed.

Adolescent basketball strength training


A Binomial Identity simplify

Question: I want to symplify
$$ \sum_{\ell=1}^{k} \frac{1}{\ell}\sum_{m=1}^{\min\{\ell,k-\ell\}}\binom{\ell}{m}\binom{k-\ell-1}{m-1}.
$$
Comment: I'd say try generating functions, but then again that strikes me as the likely origin of the identities in the first place. Care to elaborate on context?
Comment: Hi this is a coefficient of a polynomial. I tried generating function but it does not help, since the summation is finite and there is an extra term $\ell$.
Comment: @SophieLL How did you obtain $c_{ij}$? Where it´s from?
Comment: They are coefficients of a polynomial.
Comment: Why did you completely change the question?
Answer: Too long for a comment. It is advantageous to write your quantity as:
$$
c_{ij}^k  =k\sum_{\ell=1}^{k-1}\sum_{m=0}^{\ell}\sum_{c=0}^m\frac{1}{\ell} \left(-1\right)^{\ell-i} \binom{\ell}{m}\binom{k-\ell-1}{m-1}\binom{m}{c} \binom{k-2m}{i + j -2c -\ell}\binom{m}{\ell+c-i},
$$
where $k$ is assumed to be larger than $1$.
According to numerical experiments the quantity can be expressed by the following closed form:
$$
c_{ij}^k=\begin{cases}
\hphantom{-}\binom{k}{i},& j=0\text{ or } j=k,\ 1\le i\le k-1;\\
-\binom{k}{j},& i=0\text{ or } i=k,\ 1\le j\le k-1;\\
\hphantom{-}\hphantom{-}0,& \text{in all other cases},
\end{cases}\tag1
$$
which can be written in one line as:
$$
c_{ij}^k=(\delta_{j0}+\delta_{jk})\binom ki-(\delta_{i0}+\delta_{ik})\binom kj.\tag2
$$
Hope, this can help.
Comment: actually, for i=0, or j=0, it is not zero either, but these are trivial. The only zeros should be cases when i and j both equal to 0 or both equal to k, and the case I mentioned above.
Comment: Thank you so much! I have proved for the other two cases but the zero cases ><
Comment: The zero case is so hard to prove...
Comment: @SophieLL It would be useful if you include in your question the proof of the "non-zero" case. Besides, the formulation of the problem in your question is a little bit misleading, as $c_{ij}^k=0$ in almost all cases and not only if both inequalities $1\leq i \leq k-1$, and $1\leq j\leq k-1$ are satisfied.
Answer: Here is some information for odd $k=2K+1$ regarding a more symmetric representation which could be somewhat easier to show. A similar approach might work for the even case. We split
\begin{align*}
\sum_{l=1}^{2K}&\frac{(-1)^l}{l}\sum_{m=1}^{\min\{l,2K+1-l\}}\binom{l}{m}\binom{2K-l}{m-1}
\sum_{c=0}^m\binom{m}{c}\binom{2K+1-2m}{i+j-2c-l}\binom{m}{l+c-i}\\
&=\sum_{l=1}^{K}\frac{(-1)^l}{l}\sum_{m=1}^{l}\binom{l}{m}\binom{2K-l}{m-1}
\sum_{c=0}^m\binom{m}{c}\binom{2K+1-2m}{i+j-2c-l}\binom{m}{l+c-i}\tag{1}\\
&\quad+ \sum_{l=K+1}^{2K}\frac{(-1)^l}{l}\sum_{m=1}^{2K+1-l}\binom{l}{m}\binom{2K-l}{m-1}
\sum_{c=0}^m\binom{m}{c}\binom{2K+1-2m}{i+j-2c-l}\binom{m}{l+c-i}\tag{2}\\
\end{align*}
and transform the second sum (2) to get a representation which is nearly the same as the sum (1) multiplied by $-1$.

We obtain from (2)
  \begin{align*}
\sum_{l=K+1}^{2K}&\frac{(-1)^l}{l}\sum_{m=1}^{2K+1-l}\binom{l}{m}\binom{2K-l}{m-1}
\sum_{c=0}^m\binom{m}{c}\binom{2K+1-2m}{i+j-2c-l}\binom{m}{l+c-i}\\
&=\sum_{l=1}^{K}\frac{(-1)^{l+K}}{l+K}\sum_{m=1}^{K+1-l}\binom{l+K}{m}\binom{K-l}{m-1}\\
&\qquad\cdot\sum_{c=0}^m\binom{m}{c}\binom{2K+1-2m}{i+j-2c-l-K}\binom{m}{l+K+c-i}\tag{3}\\
&=\sum_{l=1}^{K}\frac{(-1)^{l+1}}{2K+1-l}\sum_{m=1}^{l}\binom{2K+1-l}{m}\binom{l-1}{m-1}\\
&\qquad\cdot\sum_{c=0}^m\binom{m}{c}\binom{2K+1-2m}{i+j-2c+l-2K-1}\binom{m}{2K+1-l+c-i}\tag{4}\\
&=\sum_{l=1}^{K}\frac{(-1)^{l+1}}{l}\sum_{m=1}^{l}\binom{2K-l}{m-1}\binom{l}{m}\\
&\qquad\cdot\sum_{c=0}^m\binom{m}{c}\binom{2K+1-2m}{i+j-2c+l-2K-1}\binom{m}{2K+1-l+c-i}\tag{5}\\
\end{align*}
Comment:

In (3) we shift the index $l$ by $K$ to start with $l=1$.
In (4) we change the order of summation of the outer sum $l\to K+1-l$.
In (5) we use the binomial identity $\binom{p}{q}=\frac{p}{q}\binom{p-1}{q-1}$ and transform $\frac{1}{2K+1-l}\binom{2K+1-l}{m}=\frac{1}{m}\binom{2K-l}{m-1}$ followed by $\frac{1}{m}\binom{l-1}{m-1}=\frac{1}{l}\binom{l}{m}$.

Numerical calculation indicates the sum (5) is equal to (1) times $-1$.

By putting (1) and (5) together we conclude OPs claim for odd $k=2K+1$ is equivalent with showing for $1\leq i,j\leq 2K$:
  \begin{align*}
&\color{blue}{\sum_{l=1}^{K}\frac{(-1)^l}{l}\sum_{m=1}^{l}\binom{l}{m}\binom{2K-l}{m-1}
\sum_{c=0}^m\binom{m}{c}}\\
&\ \ \color{blue}{\cdot\left[\binom{2K+1-2m}{i+j-2c-l}\binom{m}{l+c-i}-\binom{2K+1-2m}{i+j-2c+l-2K-1}\binom{m}{2K+1-l+c-i}\right]}\\
&\ \ \color{blue}{=0}\tag{6}
\end{align*}

Add-on  2019-07-07: Two aspects.
Up to now I couldn't find an answer but here is some additional information which might be helpful when looking for an answer. Using the coefficient of operator $[z^n]$ to denote the coefficient of $z^n$ of a (formal Laurent) series $A(z)$ we can write for instance
\begin{align*}
[z^k](1+z)^n=\binom{n}{k}\tag{7}
\end{align*}
This notation (7) is strongly related with Egorychev's method $$\mathop{res}_z\frac{A(z)}{z^{M+1}}=[z^{-1}]z^{-M-1}A(z)=[z^M]A(z)$$ where many great examples can be found in his book Integral Representation and the Computation of Combinatorial Sums.

We can transform the inner sum of (1) to
\begin{align*}
\sum_{c=0}^m&\binom{m}{c}\binom{2K+1-2m}{i+j-2c-l}\binom{m}{l+c-i}\\
&=\sum_{c=0}^m\binom{m}{c}[z^{i+j-2c-l}](1+z)^{2K+1-2m}[u^{l+c-i}](1+u)^m\\
&=[z^{i+j-l}](1+z)^{2K+1-2m}[u^{l-i}](1+u)^m\sum_{c=0}^m\binom{m}{c}\left(\frac{z^2}{u}\right)^c\\
&=[z^{i+j-l}](1+z)^{2K+1-2m}[u^{l-i}](1+u)^m\left(1+\frac{z^2}{u}\right)^m\\
\end{align*}
Similarly transforming (5) we obtain
\begin{align*}
\sum_{c=0}^m&\binom{m}{c}\binom{2K+1-2m}{i+j-2c+l-2K-1}\binom{m}{2K+1-l+c-i}\\
&=\sum_{c=0}^m\binom{m}{c}[z^{i+j-2c+l-2K-1}](1+z)^{2K+1-2m}[u^{2K+1-l+c-i}](1+u)^m\\
&=[z^{i+j+l-2K-1}](1+z)^{2K+1-2m}[u^{2K+1-l-i}](1+u)^m\sum_{c=0}^m\binom{m}{c}\left(\frac{z^2}{u}\right)^c\\
&=[z^{i+j+l-2K-1}](1+z)^{2K+1-2m}[u^{2K+1-l-i}](1+u)^m\left(1+\frac{z^2}{u}\right)^m\\
&=[z^{i+j-l}](1+z)^{2K+1-2m}[u^{l-i}](1+u)^m\left(1+\frac{z^2}{u}\right)^m\left(\frac{z}{u}\right)^{2K+1-l}\\
\end{align*}
Putting all together we obtain analogously to (6) OP's claim for odd $k=2K+1$ is equivalent with showing that
\begin{align*}
&\color{blue}{[z^{i+j}u^{-i}](1+z)^{2K+1}\sum_{l=1}^{K}\frac{(-1)^l}{l}\left(\frac{z}{u}\right)^{l}\left(1-\left(\frac{z}{u}\right)^{2K+1-2l}\right)}\\
&\qquad\color{blue}{\cdot\sum_{m=1}^{l}\binom{l}{m}\binom{2K-l}{m-1}
\left(\frac{1+u}{1+z}\right)^m\left(1+\frac{z^2}{u}\right)^m
=0}\tag{8}\\
\end{align*}
Note that in (8) the factor $(1+z)^m$ in the denominator can be cancelled due to  $(1+z)^{2K+1}$ as well as the factors $u^{p}$ in the denominator can be merged into the coefficient of operator. So, we are comparing coefficients of a bivariate polynomial in $z$ and $u$. We have a situation similar to (6) but it is not easy to see how this can be simplified in order to show the claim.
We take a look at (6) again and write the claim as
\begin{align*}
 &\sum_{l=1}^{K}\frac{(-1)^l}{l}\sum_{m=1}^{l}\binom{l}{m}\binom{2K-l}{m-1}\\
&\qquad\cdot\sum_{c=0}^m\binom{m}{c}\binom{2K+1-2m}{i+j-2c-l}\binom{m}{l+c-i}\\
&=\sum_{l=1}^{K}\frac{(-1)^l}{l}\sum_{m=1}^{l}\binom{l}{m}\binom{2K-l}{m-1}\\
&\qquad\cdot\sum_{c=0}^m\binom{m}{c}\binom{2K+1-2m}{i+j-2c+l-2K-1}\binom{m}{2K+1-l+c-i}\\
 \end{align*}
Calculations for small values of $1\leq i,j\leq 2K$ show  the number of non-zero terms of the LHS and of the RHS differ. This indicates that a detailed analysis of the variable range of the LHS which give non-zero terms:
\begin{align*}
  &1\leq l\leq m\\
&0\leq m-1\leq 2K-l\\
&0\leq i+j-2c-l\leq 2K+1-2m\\
&0\leq l+c-i\leq m
  \end{align*}
and similarly inspection of the variable range of the RHS might give indications of nice linear transformations of index variables. This way we could transform LHS and RHS to get simpler representations from which the claim can be derived easily. Alas, due to the rather complicated relationship of the index variables this job looks cumbersome.
Comment: @SophieLl: I know it's just a first step simplifying the upper limit of the sum with index $m$. It looks promising that the part (1) and (5) are the same besides a factor $-1$. But, admittedly this main step is left open and has to be shown. I'll work on it at the weekend.
Comment: @SophieLL: I'm sorry, but despite a considerable amount of time I've tried to find a solution I wasn't successful.
Comment: Hi, @markusscheuer, thank you so much for helping me!!! However, I am still confused about why (5) is equal to - (1). Do you mind illustrating a little bit more on this?
Comment: I think if we replace $\ell$ as $2k-\ell+1$, we can still get (5), but it is not obvious how we can show that (5)=-(1), since $1 \le \ell \le K$  in the above setting ><
Comment: Thank you so much! I am still working on trying other ways to show, but still don't know how to show it.
Comment: @RockyLi: Many thanks for granting the bounty.
Answer: By way of an extended comment in response to a pers. comm. / request. A conjectured alternate representation of the sum (here $i=p$ and $j=q$) is given by
$$k (-1)^p \mathrm{Res}_{z=0} z^{p-1}
[w^{p+q}] (1+w)^{k}
[v^{k}] (1+v)^{k-1} \\ \times
\sum_{\ell\ge 1} \frac{(-1)^\ell}{\ell}
z^{-2\ell} w^\ell (1+w)^{-2\ell}
v^\ell (1+v)^{-\ell}
(z(1+w)^2+v(1+z)(z+w^2))^\ell.$$
At this point the term in $1/\ell$ introduces a logarithm and the power term in $\ell$ does not factorize / collect easily in $z$ or $w.$
Comment: @MarkoRiedel: Many thanks for your support and evaluation. (+1)
Comment: Thank you so much! I totally understand... I have no idea either...

A Binomial Identity simplify