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  • What is a 'good number' of exceptions to implement for my library?

    - by Fuzz
    I've always wondered how many different exception classes I should implement and throw for various pieces of my software. My particular development is usually C++/C#/Java related, but I believe this is a question for all languages. I want to understand what is a good number of different exceptions to throw, and what the developer community expect of a good library. The trade-offs I see include: More exception classes can allow very fine grain levels of error handling for API users (prone to user configuration or data errors, or files not being found) More exception classes allows error specific information to be embedded in the exception, rather than just a string message or error code More exception classes can mean more code maintenance More exception classes can mean the API is less approachable to users The scenarios I wish to understand exception usage in include: During 'configuration' stage, which might include loading files or setting parameters During an 'operation' type phase where the library might be running tasks and doing some work, perhaps in another thread Other patterns of error reporting without using exceptions, or less exceptions (as a comparison) might include: Less exceptions, but embedding an error code that can be used as a lookup Returning error codes and flags directly from functions (sometimes not possible from threads) Implemented an event or callback system upon error (avoids stack unwinding) As developers, what do you prefer to see? If there are MANY exceptions, do you bother error handling them separately anyway? Do you have a preference for error handling types depending on the stage of operation?

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  • Is this a decent use-case for goto in C?

    - by Robz
    I really hesitate to ask this, because I don't want to "solicit debate, arguments, polling, or extended discussion" but I'm new to C and want to gain more insight into common patterns used in the language. I recently heard some distaste for the goto command, but I've also recently found a decent use-case for it. Code like this: error = function_that_could_fail_1(); if (!error) { error = function_that_could_fail_2(); if (!error) { error = function_that_could_fail_3(); ...to the n-th tab level! } else { // deal with error, clean up, and return error code } } else { // deal with error, clean up, and return error code } If the clean-up part is all very similar, could be written a little prettier (my opinion?) like this: error = function_that_could_fail_1(); if(error) { goto cleanup; } error = function_that_could_fail_2(); if(error) { goto cleanup; } error = function_that_could_fail_3(); if(error) { goto cleanup; } ... cleanup: // deal with error if it exists, clean up // return error code Is this a common or acceptable use-case of goto in C? Is there a different/better way to do this?

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  • Why does Android make good coding so difficult?

    - by metacircle
    my daily work is writing tools in C#/WPF. After over more than 1 year on the job now, I came to love MVVM, IoC Containers, XAML (and more). It's pure fun to write code, since simple, maintainable and extendable code just comes naturally when you follow a few basic patterns. In my free time I really want to write some apps, mainly for my own personal use. I want to write apps for fun and not to make money or anything, that being said, paying an annual fee to be allowed to use my own apps on my own device is a total no-go for me. So I am not able to code for Windows Phone and am also not able to use Xamarin on Android (which is sad since Visual Studio + Resharper is programmers heaven). So I am stuck with Android "classic" Java development. Everytime I sit down at home to create an app, or improve some of the code I have already written I get annoyed very quick because getting good, decoupled code is just so hard to accomplish. It feels like everything you have to do in Android to create a good architecture is a workaround instead of being the way things are meant to be. Writing the UI in xml is fine, but everything else is one big code mess. Even all the tutorials do all their coding in the code behind. For 'hello world' this is fine, but for anything bigger this gets messy very very quick. This is where the fun for me ends. It's just no fun anymore because I just spend 90% of my time refactoring and thinking of workarounds how to make my code more maintainable with all the restrictions Android puts on me. Am I missing a crucial part or is this just the way Android is meant to be? Do you have any suggestions how to learn 'the fun way' of Android programming.

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  • design an extendible and pluggable business logic flow handler in php

    - by Broncha
    I am working on a project where I need to allow a pluggable way to inject business processes in the normal data flow. eg There is an ordering system. The standard flow of the application is A consumer orders an item. Pays for it and card is authorized. Admin captures the payment. Order is marked as complete and item is shipped. But this process may vary (extra steps in between) for different clients. Say a client would need to validate the location of the consumer before he is presented with a credit card form, OR his policies might require some other processes in between. I am thinking of using State Pattern for processing orders, saving the current state of the order in database, and initializing the state of order from the saved state. I would also need some mechanism, where a small plugin would be able to inject business specific states in the state machine. Am I thinking the right way? Are there already implemented patterns for this kind of situation? I am working with Codeigniter and basically this would mean for me, to redirect to proper controller according to the current state of the order. Like, if the state of the order is unconfirmed then redirect the user to details page and then change the state to pending. If some client would need to do some validation, then register an intermediate state between unconfirmed and pending Please suggest.

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  • Preferred way for dealing with customer-defined data in enterprise application

    - by Axarydax
    Let's say that we have a small enterprise web (intranet) application for managing data for car dealers. It has screens for managing customers, inventory, orders, warranties and workshops. This application is installed at 10 customer sites for different car dealers. First version of this application was created without any way to provide for customer-specific data. For example, if dealer A wanted to be able to attach a photo to a customer, dealer B wanted to add e-mail contact to each workshop, and dealer C wanted to attach multiple PDF reports to a warranty, each and every feature like this was added to the application, so all of the customers received everything on new update. However, this will inevitably lead to conflicts as the number of customers grow as their usage patterns are unique, and if, for instance, a specific dealer requested to have an ability to attach (for some reason) a color of inventory item (and be able to search by this color) as a required item, others really wouldn't need this feature, and definitely will not want it to be a required item. Or, one dealer would like to manage e-mail contacts for their employees on a separate screen of the application. I imagine that a solution for this is to use a kind of plugin system, where we would have a core of the application that provides for standard features like customers, inventory, etc, and all of the customer's installed plugins. There would be different kinds of plugins - standalone screens like e-mail contacts for employees, with their own logic, and customer plugin which would extend or decorate inventory items (like photo or color). Inventory (customer,order,...) plugins would require to have installation procedure, hooks for plugging into the item editor, item displayer, item filtering for searching, backup hook and such. Is this the right way to solve this problem?

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  • What's the point of the Prototype design pattern?

    - by user1905391
    So I'm learning about design patterns in school. Many of them are silly little ideas, but nevertheless solve some recurring problems(singleton, adapters, asynchronous polling, ect). But today I was told about the so called 'Prototype' design pattern. I must be missing something, because I don't see any benefits from it. I've seen people online say it's faster than using "new"' but this is doesn't make any sense, since at some point, regardless how the new object is created, memory needs to be allocated for it ect. Furthermore, doesn't this pattern run in the same circles as the 'chicken or egg' problem? By this I mean, since the prototype pattern essentially is just cloning objects, at some point the original object must be created itself (ie, not cloned). So this would mean, that I would need to have an existing copy of every object that I would ever want to clone already ready to clone? Seems stupid to me. Can anyone explain what the use of this pattern is? Original post: http://stackoverflow.com/questions/13887704/whats-the-point-of-the-prototype-design-pattern

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  • C#.NET: How to update multiple .NET pages when a particular event occurs in one .Net page? In another words how to use Observer pattern(Publish and subscribe to events)

    Problem: Suppose you have a scenario in which you have to update multiple pages when an event occurs in main page. For example imagine you have a main page where you are dispalying a tab control. This tab control has 3 tab pages where you are loading 3 different user controls. On click of an update button in main page imagine if you have do something in all the 3 tab panels. In other words an event in main page has to be handled in many other pages. An event in main page which contains the tab control has to be handled in all the tab panels(user controls) Answer: Use Observer pattern Define a base page for the page that contains the tab control. Main page which contains the tab: Baseline_Baseline Basepage for the above main page: BaselineBasePage User control that has to be udpated for an event in main page: Baseline_PriorNonDeloitte Source Code: public class BaselineBasePage : System.Web.UI.Page { IList lstControls = new List(); public void Add(IObserver userControl) { lstControls.Add(userControl); } public void Remove(IObserver userControl) { lstControls.Remove(userControl); } public void RemoveAllUserControls() { lstControls.Clear(); } public void Update(SaveEventArgs e) { foreach (IObserver LobjControl in lstControls) { LobjControl.Save(e); } } } public interface IObserver { void Update(SaveEventArgs e); } public partial class Baseline_Baseline : BaselineBasePage { . . . this.Add(_ucPI); this.Add(_ucPI1); protected void abActionBar_saveClicked(object sender, EventArgs e) { SaveEventArgs se = new SaveEventArgs(); se.TabType = (BaselineTabType)tcBaseline.ActiveTabIndex; this.Update(se); } } Public class Baseline_PriorNonDeloitte : System.Web.UI.UserControl,IObserver { public void Update(SaveEventArgs e) { } } More info at: http://www.dofactory.com/Patterns/PatternObserver.aspx span.fullpost {display:none;}

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  • C# Domain-Driven Design Sample Released

    - by Artur Trosin
    In the post I want to declare that NDDD Sample application(s) is released and share the work with you. You can access it here: http://code.google.com/p/ndddsample. NDDDSample from functionality perspective matches DDDSample 1.1.0 which is based Java and on joint effort by Eric Evans' company Domain Language and the Swedish software consulting company Citerus. But because NDDDSample is based on .NET technologies those two implementations could not be matched directly. However concepts, practices, values, patterns, especially DDD, are cross-language and cross-platform :). Implementation of .NET version of the application was an interesting journey because now as .NET developer I better understand the differences positive and negative between these two platforms. Even there are those differences they can be overtaken, in many cases it was not so hard to match a java libs\framework with .NET during the implementation. Here is a list of technology stack: 1. .net 3.5 - framework 2. VS.NET 2008 - IDE 3. ASP.NET MVC2.0 - for administration and tracking UI 4. WCF - communication mechanism 5. NHibernate - ORM 6. Rhino Commons - Nhibernate session management, base classes for in memory unit tests 7. SqlLite - database 8. Windsor - inversion of control container 9. Windsor WCF facility - for better integration with NHibernate 10. MvcContrib - and in particular its Castle WindsorControllerFactory in order to enable IoC for controllers 11. WPF - for incident logging application 12. Moq - mocking lib used for unit tests 13. NUnit - unit testing framework 14. Log4net - logging framework 15. Cloud based on Azure SDK These are not the latest technologies, tools and libs for the moment but if there are someone thinks that it would be useful to migrate the sample to latest current technologies and versions please comment. Cloud version of the application is based on Azure emulated environment provided by the SDK, so it hasn't been tested on ‘real' Azure scenario (we just do not have access to it). Thanks to participants, Eugen Gorgan who was involved directly in development, Ruslan Rusu and Victor Lungu spend their free time to discuss .NET specific decisions, Eugen Navitaniuc helped with Java related questions. Also, big thank to Cornel Cretu, he designed a nice logo and helped with some browser incompatibility issues. Any review and feedback are welcome! Thank you, Artur Trosin

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  • Is there a language or design pattern that allows the *removal* of object behavior or properties in a class hierarchy?

    - by Sebastien Diot
    A well-know shortcoming of traditional class hierarchies is that they are bad when it comes to model the real world. As an example, trying to represent animals species with classes. There are actually several problems when doing that, but one that I never saw a solution to is when a sub-class "looses" a behavior or properties that was defined in a super-class, like a penguin not being able to fly (there are probably better examples, but that's the first one that comes to my mind, having seen "Madagascar 2" recently). On the one hand, you don't want to define for every property and behavior some flag that specifies if it is at all present, and check it every time before accessing that behavior or property. You would just like to say that birds can fly, simply and clearly, in the Bird class. But then it would be nice if one could define "exceptions" afterward, without having to use some horrible hacks everywhere. This often happens when a system has been productive for a while. You suddenly find an "exception" that doesn't fit in the original design at all, and you don't want to change a large portion of your code to accommodate it. So, is there some language or design patterns that can cleanly handle this problem, without requiring major changes to the "super-class", and all the code that uses it? Even if a solution only handle a specific case, several solutions might together form a complete strategy. [EDIT] Forgot about the Liskov Substitution Principle. That is why you can't do it. Assuming you define "traits/interfaces" for all major "feature groups", you can freely implement traits in different branches of the hierarchy, like the Flying trait could be implemented by Birds, and some special kind of squirrels and fish. So my question could amount to "How could I un-implement a trait?" If your super-class is a Java Serializable, you have to be one too, even if there is no way for you to serialize your state, for example if you contained a "Socket". So one way to do it is to always define all your traits in pair from the start: Flying and NotFlying (which would throw UnsupportedOperationExceiption, if not checked against). The Not-trait would not define any new interface, and could be simply checked for. Sounds like a "cheap" solution, in particular if used from the start.

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  • What is the right way to group this project into classes?

    - by sigil
    I originally asked this on SO, where it was closed and recommended that I ask it here instead. I'm trying to figure out how to group all the functions necessary for my project into classes. The goal of the project is to execute the following process: Get the user's FTP credentials (username & password). Check to make sure the credentials establish a valid connection to the FTP server. Query several Sharepoint lists and join the results of those queries to create a list of items that need to have action taken on them. Each item in the list has a folder. For each item: Zip the contents of the folder. Upload the folder to the FTP server using SFTP Update the item's Sharepoint data. Email the user an Excel report showing, e.g., Items without folder paths Items that failed to zip or upload Steps 2-5 are performed on a periodic basis; if step 2 returns an invalid connection, the user is alerted and the process returns to step 1. If at any point the user presses a certain key, the process terminates. I've defined the following set of classes, each of which is in its own .cs file: SFTP: file transfer processes DataHandler: Sharepoint data retrieval/querying/updating processes. Also makes and uploads the zip files. Exceptions: Not just one class, this is the .cs file where I have all of my exception classes. Report: Builds and sends the report. Program: The main class for running the program. I recognize that the DataHandler class is a god object, but I don't have a good idea of how to refactor it. I feel like it should be more fine-grained than just breaking it into Sharepoint, Zip, and Upload, but maybe that's it. Also, I haven't yet worked out how to combine the periodic behavior with the "wait for user input at any point in the process" part; I think that involves threads, which means other classes to manage the threads... I'm not that well-versed in design patterns, but is there one that fits this project well? If this is too big of a topic to neatly explain in an SO answer, I'll also accept a link to a good tutorial on what I'm trying to do here.

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  • Uncrackable anti-piracy protection/DRM even possible? [closed]

    - by some guy
    I hope that this is programming-related enough. You have probably heard about Ubisofts recent steps against piracy. (New DRM requires a constant connection to the Ubisoft server) Many people including me see this as intolerable because the only ones suffering from it at the end are the paying customers. Now to the actual question(s): Ubisoft justified this by calling this mechanism "Uncrackable, only playable by the paying customers". Is a so called uncrackable DRM even possible? You can reverse-engineer and modify everything, even if it takes long. Isn't Ubisoft already lying by calling something not crackable? I mean, hey - With the game you get all its content (textures, models, you know) and some anti-piracy mechanism hardcoded into it. How could that be "uncrackable"? You can just patch the unwanted mechanisms out ---- "Pirates" play the cracked game without problems and the paying customers are the idiots by having constant problems with the game and being unable to play it without a (working) internet connection. What are the points Ubisoft sees in this? If they are at least a bit intelligent and informed they know their anti-piracy protection won't last long. All they get is lower sales, angry customers and happy pirates and crackers.

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  • how to access anti aliasing method of a font with CSS

    - by Daniel Ramirez-Escudero
    I've had this problem in a lot of different webs. You have a font which has different anti-aliasing options, the designer uses the same font with different anti-aliasing options on different parts of the text on the web. So there is a difference between some elements. In this case I have sharp, crisp, strong and smooth. I've used a font generator to get the code to access it via @font-face. Even so, I also have the original .otf if important to know. Is there a method to access this? I upload a picture of what I mean and my actual code: ![@font-face { font-family: 'light'; src: url('../_fnt/light/gothamrnd-light.eot'); src: url('../_fnt/light/gothamrnd-light.eot?#iefix') format('embedded-opentype'), url('../_fnt/light/gothamrnd-light.woff') format('woff'), url('../_fnt/light/gothamrnd-light.ttf') format('truetype'), url('../_fnt/light/gothamrnd-light.svg#../_fnt/light/gothamrnd-light') format('svg'); font-weight: normal; font-style: normal; }]![enter image description here][1]

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  • Artifacts when trying to draw background grid without anti-aliasing in a QGraphicsScene

    - by estan
    Hi folks, I'm trying to draw a background grid in the drawBackground() function of my QGraphicsScene subclass: void Scene::drawBackground(QPainter *painter, const QRectF &rect) { const int gridSize = 50; const int realLeft = static_cast<int>(std::floor(rect.left())); const int realRight = static_cast<int>(std::ceil(rect.right())); const int realTop = static_cast<int>(std::floor(rect.top())); const int realBottom = static_cast<int>(std::ceil(rect.bottom())); // Draw grid. const int firstLeftGridLine = realLeft - (realLeft % gridSize); const int firstTopGridLine = realTop - (realTop % gridSize); QVarLengthArray<QLine, 100> lines; for (qreal x = firstLeftGridLine; x <= realRight; x += gridSize) lines.append(QLine(x, realTop, x, realBottom)); for (qreal y = firstTopGridLine; y <= realBottom; y += gridSize) lines.append(QLine(realLeft, y, realRight, y)); //painter->setRenderHint(QPainter::Antialiasing); painter->setPen(QPen(QColor(220, 220, 220), 0.0)); painter->drawLines(lines.data(), lines.size()); // Draw axes. painter->setPen(QPen(Qt::lightGray, 0.0)); painter->drawLine(0, realTop, 0, realBottom); painter->drawLine(realLeft, 0, realRight, 0); } However, unless I turn on anti-aliasing, moving items around will sometimes leave artifacts in the grid (areas where it's not drawn). It seems it mostly happens at low zoom levels, when the view is zoomed out a bit. Any ideas what I might be doing wrong here? I'd really don't want to turn anti-aliasing on since the lines are strictly horizontal and vertical, and I'd like them to be as crisp as possible. Any help is much appriciated, Regards, Elvis

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  • How do I stop Sophos anti virus from scanning directories that are under source control

    - by user26453
    From googling it seems its well known that SophosAV as well as other AV programs have issues with how they interact and can inhibit source control utilities like TortoiseHG or TortoiseSVN. One solution is to exclude directories under source control from on-access scanning as detailed here on Sophos's support site. There is a corollary article that mentions some issues related to this, namely the need to place multiple entries for exclusions based on the possibility of the location being accessed through the short vs. long name (e.g., Progra~1 vs. "Program Files"). One other twist is I am using a junction to relocate my user directory, C:\Users\Username, to a second hard drive, E:. Since I am not sure how this interacts I have included the source control directory as they are nested in both locations. As a result, I have included the two exclusions for the on-access scanning exclusions (and to be on the safe side on-demand exclusions as well, although this should only come into play when I select a parent directory of the exclusion to be scanned on-demand, but still). You'll notice I have no need to add extra exclusions for those locations based on short vs. long name distinctions. The two exclusion I have then, for both on-access and on-demand scanning exclusions are: C:\Users\Username\source-control-directory E:\source-control-directory However, this does not seem to work as TortoiseHG still lags terribly in response to any request as AV software starts scanning when the directory is accessed via TortoiseHG. I can verify without a doubt that Sophos is causing the problems: I can completely disable on-access scanning. Once this is done TortoiseHG responds very fast to all operations. I cannot leave this disabled obviously, but since the exclusion don't seem to be working, what next?

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  • Running make for Nginx throws a “multiple target patterns” error

    - by Justin Meltzer
    When I run make inside my installed nginx directory I get the output: make -f objs/Makefile make[1]: Entering directory `/home/ec2-user/nginx/nginx-1.2.4' objs/Makefile:110: *** multiple target patterns. Stop. make[1]: Leaving directory `/home/ec2-user/nginx/nginx-1.2.4' make: * [build] Error 2 I am on an Amazon Linux AMI. The steps I took from the beginning was wget /path/to/nginx/tarball tar xvf nginx-1.2.4.tar.gz cd nginx-1.2.4 ./configure --prefix=/nginx --a-bunch-of-other-options Then I ran make. Also I installed make by running sudo yum install make Please let me know if there's any other information I should be providing.

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  • clam anti-virus is slowing down my server performance

    - by Scarface
    Hey guys, I just installed clam av http://sourceforge.net/projects/php-clamav/ for scanning file uploads on my linux VPN running php. The problem is that for some reason just initiating the extension in the php ini file slows down my entire network. Regular requests such as changing pages that should take less than 1 second take 5. Has anyone ever experienced this before or have a good virus scanning alternative for scanning file uploads? extension=clamav.so [clamav] clamav.dbpath="/usr/share/clamav" clamav.keeptmp=20 clamav.maxreclevel=16 clamav.maxfiles=10000 clamav.maxfilesize=26214400 clamav.maxscansize=104857600 clamav.keeptmp=0

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  • Anti-virus for Ubuntu Hardy 8.04

    - by April
    I am using Ubuntu hardy with Scalr and AWS, the Ubuntu instance does not come with any antivirus software. Can anyone recommend a good ant-virus software for Ubuntu? I would also need installation and config steps. Thanks.

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  • clam anti-virus is slowing down my server performance significantly

    - by Scarface
    Hey guys, I just installed clam av http://sourceforge.net/projects/php-clamav/ for scanning file uploads on my linux VPN running php. The problem is that for some reason just initiating the extension in the php ini file slows down my entire network. Regular requests such as changing pages that should take less than 1 second take 5. Has anyone ever experienced this before or have a good virus scanning alternative for scanning file uploads? extension=clamav.so [clamav] clamav.dbpath="/usr/share/clamav" clamav.keeptmp=20 clamav.maxreclevel=16 clamav.maxfiles=10000 clamav.maxfilesize=26214400 clamav.maxscansize=104857600 clamav.keeptmp=0

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  • Anti-virus for Ubuntu Hardy 8.04

    - by April
    I am using Ubuntu hardy with Scalr and AWS, the Ubuntu instance does not come with any antivirus software. Can anyone recommend a good ant-virus software for Ubuntu? I would also need installation and config steps. Thanks.

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  • anti-virus / malware solution for small non-profit network

    - by Jason
    I'm an IT volunteer at a local non-profit. I'm looking for a good AV/malware solution. We currently use a mishmash of different client solutions, and want to move to something centralized. There is no full time IT staff. What I'm looking for: centralized administration - server is Windows Server 2003 minimal admin overhead ability to do e-mail notification/alerts/reporting would be very cool 10-25 XP Clients (P3/P4 hardware) free or discounted solution for non-profits We can get a cheap license for Symantec Endpoint Protection. My past experience with Symantec has been bad, but I've heard good things about this product. However, I've also read that it's kind of a nightmare to setup and administer, and may not be worth it for the size of our network.

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  • Anti Virus automatic update problem with linux squid proxy

    - by Kumar P
    I am using RHEL 5 linux server with 10 Windows XP client machines, I installed bit defender internet security 2009 in my windows machines, My Problem is automatic updates are not performing, I get following error I can't find what i want to do changes in my proxy. I am using squid 2.6 stable When i use Norton , get same error. What i want to do, for update it ?

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  • Unable to install Kaspersky anti virus 2011 on XP

    - by Guruprasad
    I recently tried installing Kaspersky antivirus 2011 on my XP (service pack 2) . Everytime I try to install through setup file, it initiates and then I get a pop up message saying Windows XP not compatible ( Sorry could no get the complete error message ) there is also options which come up saying "continue anyway" but it wont allow to click as the system gets hung . I also tried to skip from incompatible software by following the instructions on Kaspersky's website by creating a short cut to setup file and modifying the target field in it but still I get the same message. It also asks me to reboot before I install but it is still the same . Does this mean that I wont be able to install this antivirus software on my machine ? I also wrote to the Kaspersky support but seems they will take ages to reply.

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  • How do anti-viruses work?

    - by Phoshi
    So I was thinking about viruses recently, and wondering how exactly antiviruses keep up? Considering anybody who'd been coding for a few weeks could hack together something do do nasty, nasty things to somebody's PC, the quantity alone would make a simple list of hashes prohibitive, so how do antiviruses do it? Do they monitor process activity and have a 3 strikes rule for doing virus-like things? And if so, what's stopping it from triggering on perfectly harmless things (like me moving files around in \system32)? I did a bit of googling, but the regular places didn't particularly help, and I couldn't find a dupe here, so I thought it'd be good to ask :)

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