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• How to decide whether to implement an operation as Entity operation vs Service operation in Domain Driven Design?

  - by Louis Rhys

  I am reading Evans's Domain Driven Design. The book says that there are entity and there are services. If I were to implement an operation, how to decide whether I should add it as a method on an entity or do it in a service class? e.g. myEntity.DoStuff() or myService.DoStuffOn(myEntity)? Does it depend on whether other entities are involved? If it involves other entities, implement as service operation? But entities can have associations and can traverse it from there too right? Does it depend on stateless or not? But service can also access entities' variable, right? Like in do stuff myService.DoStuffOn, it can have code like if(myEntity.IsX) doSomething(); Which means that it will depend on the state? Or does it depend on complexity? How do you define complex operations?

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• Rails - How to use modal form to add object in one model, then reflect that change on main page?

  - by Jim

  I'm working on a Rails app and I've come across a situation where I'm unsure of the cleanest way to proceed. I posted a question on SO with code samples and such - it has received no answers, and the more I think about the problem, the more I think I might be approaching this the wrong way. (See the SO question at http://stackoverflow.com/questions/9521319/how-to-reference-form-when-rendering-partial-from-js-erb-file) So, in more of a generic architecture type question: Right now I have a form where a user can add a new recipe. The form also allows the user to select ingredients (it uses a collection_select which contains Ingredient.all). The catch is - I'd like the user to be able to add a new ingredient on the fly, without leaving the recipe form. Using a hidden div and some jQuery/AJAX, I have a link the user can click to popup a modal form containing ingredients/new.html.erb which is a simple form. When that form is submitted, I call ingredients/create.js.erb to validate the ingredient was saved and hide the modal div. Now I am back to my recipe form, but my collection_select hasn't updated. It seems I have a few choices here: try and re-render the collection_select portion of the form so it grabs a new list of ingredients. This was the method I was attempting when I wrote the SO question. The problem I run into is the partial I use for the collection_select needs the parent form passed in, and when I try and render from the JS file I don't know how to pass it the form object. Reload the recipe form. This works (the collection_select now contains the new ingredient), but the user loses any progress they made on the recipe form. I would need a way to persist the form data - I thought about manually passing the values back and forth, but that is sloppy and there has to be a better way... Try and manually insert the tags using jQuery - this would be simple, but because I'm allowing for multiple ingredients to be added, I can't be certain what ID to target. Now, I can't be the only person to have this issue - so is there an easier way I'm missing? I like option 2 above, but I don't know if there's an easy way to grab the entire params hash as if I had submitted the main recipes form. Hopefully someone can point me in the right direction so I can find an answer to this... If this doesn't make any sense at all, let me know - I can post code samples if you want, but most of the pertinent code is up on the SO question. Thanks!

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• Better solution then simple factory method when concrete implementations have different attributes

  - by danip

  abstract class Animal { function eat() {..} function sleep() {..} function isSmart() } class Dog extends Animal { public $blnCanBark; function isSmart() { return $this->blnCanBark; } } class Cat extends Animal { public $blnCanJumpHigh; function isSmart() { return $this->blnCanJumpHigh; } } .. and so on up to 10-20 animals. Now I created a factory using simple factory method and try to create instances like this: class AnimalFactory { public static function create($strName) { switch($strName) { case 'Dog': return new Dog(); case 'Cat': return new Cat(); default: break; } } } The problem is I can't set the specific attributes like blnCanBark, blnCanJumpHigh in an efficient way. I can send all of them as extra params to create but this will not scale to more then a few classes. Also I can't break the inheritance because a lot of the basic functionality is the same. Is there a better pattern to solve this?

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• What are some good Software Engineering books for people who didn't formally study Computer Science or Software Engineering?

  - by Kugathasan Abimaran

  I'm a graduate in the electronic & telecommunication field, but working in a software company. I want to continue in this field and going for Masters in it. Can you recommend me some of the best books on software engineering, which cover almost all the topics in software engineering. I am not looking for books about coding practices such as Code Complete, Pragmatic Programmer, but rather general software engineering references.

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• How do you handle measuring Code Coverage in JavaScript

  - by Dancrumb

  In order to measure Code Coverage for JavaScript unit tests, one needs to instrument the code, run the tests and then perform post-processing. My concern is that, as a result, you are unit testing code that will never be run in production. Since JavaScript isn't compiled, what you test should be precisely what you execute. So here's my question, how do you handle this? One thought I had was to run Unit Testing on the production code and use that for my pass fail. I would then create a shadow of my production code, with instrumentation and run my unit tests again; this would give me my code coverage stats. Has anyone come across a method that is a little more graceful than this?

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• Strategies for Indexing Custom Fields in RavenDB

  - by Adrian Thompson Phillips

  In the relational database world, if I was developing a CRM system and wanted to have the user add their own custom fields that are searchable, I could have tables that store the name of the new column, the data type and the value, etc. (which would be less inefficient to index) or I could use the less elegant (but more searchable) solution that software like Dynamics and SharePoint use, whereas I create a load of columns on my aggregate root called CustomInt1, CustomInt2, etc. (which looks dirty and has a limit of how many custom fields a user can have, but has indexing advantages). But my questions is this, in NoSQL databases, what would be the best way of achieving the same thing? My priority would be for searchability. So what would be the best way to store this data? If I used a predefined set of properties (i.e. CustomData1, CustomData2, etc.), because these are all stored as JSON (i.e. strings) in the database, does this make it simpler because I don't have to worry about data types?

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• Rule of thumb for cost vs. savings for code re-use

  - by Styler

  Is it a good rule of thumb to always write code for the intent of re-using it somewhere down the road? Or, depending on the size of the component you are writing, is it better practice to design it for re-use when it makes sense with regards to time spent on it. What is a good rule of thumb for spending extra time on analysis and design on project components that have "some probability" of being needed later down the road for other things that may or may need this part. For example, if I have the need for project X to do things A, and B. A definitely needs to be written for re-use because it just makes sense to do so. B is very project specific at the moment, and I can hack it all together in a couple days to finish the project on time and give everyone kudos for being a great team, etc. Or if we say, lets spend a whole friggin' 2 weeks figuring out what project Y/Z might need this thing for and spend a load of extra time on on part B because someday we might need to use it on project Y/Z (where the savings will be realized). I'd imagine a perfect world situation would be a nicely crafted combination of project specific vs. re-use architected components given the project. However some code shops might feel it would be a great idea to write everything for the intention of using it at some point down the road.

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• MVC + 3 tier; where ViewModels come into play?

  - by mikhairu

  I'm designing a 3-tiered application using ASP.NET MVC 4. I used the following resources as a reference. CodeProject: MVC + N-tier + Entity Framework Separating data access in ASP.NET MVC I have the following desingn so far. Presentation Layer (PL) (main MVC project, where M of MVC was moved to Data Access Layer): MyProjectName.Main Views/ Controllers/ ... Business Logic Layer (BLL): MyProjectName.BLL ViewModels/ ProjectServices/ ... Data Access Layer (DAL): MyProjectName.DAL Models/ Repositories.EF/ Repositories.Dapper/ ... Now, PL references BLL and BLL references DAL. This way lower layer does not depend on the one above it. In this design PL invokes a service of the BLL. PL can pass a View Model to BLL and BLL can pass a View Model back to PL. Also, BLL invokes DAL layer and DAL layer can return a Model back to BLL. BLL can in turn build a View Model and return it to PL. Up to now this pattern was working for me. However, I've ran into a problem where some of my ViewModels require joins on several entities. In the plain MVC approach, in the controller I used a LINQ query to do joins and then select new MyViewModel(){ ... }. But now, in the DAL I do not have access to where ViewModels are defined (in the BLL). This means I cannot do joins in DAL and return it to BLL. It seems I have to do separate queries in DAL (instead of joins in one query) and BLL would then use the result of these to build a ViewModel. This is very inconvenient, but I don't think I should be exposing DAL to ViewModels. Any ideas how I can solve this dilemma? Thanks.

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• Object oriented EDI handling in PHP

  - by Robert van der Linde

  I'm currently starting a new sub project where I will: Retrieve the order information from our mainframe Save the order information to our web-apps' database Send the order as EDI (either D01b or D93a) Receive the order response, despatch advice and invoice messages Do all kinds of fun things with the resulting datasets. However I am struggling with my initial class designs. The order information will be retrieved from the mainframe which will result in a "AOrder" class, this isn't a problem, I am not sure about how to mold this local object into an EDI string. Should I create EDIOrder/EDIOrderResponse/etc classes with matching decorators (EDIOrderD01BDecorator, EDIOrderD93ADecorator)? Do I need builder objects or can I do: // $myOrder is instance of AOrder $myOrder->toEDIOrder(); $decorator = new EDIOrderD01BDecorator($myOrder); $edi = $decorator->getEDIString(); And it'll have to work the other way around as well. Is the following code a good way of handling this problem or should I go about this differently? $ediString = $myEDIMessageBroker->fetch(); $ediOrderResponse = EDIOrderResponse::fromString($ediString); I'm just not so sure about how I should go about designing the classes and interactions between them. Thanks for reading and helping.

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• converting dates things from visual basic to c-sharp

  - by sinrtb

  So as an excercise in utility i've taken it upon myself to convert one of our poor old vb .net 1.1 apps to C# .net 4.0. I used telerik code conversion for a starting point and ended up with ~150 errors (not too bad considering its over 20k of code and rarely can i get it to run without an error using the production source) many of which deal with time/date in vb versus c#. my question is this how would you represent the following statement in VB If oStruct.AH_DATE <> #1/1/1900# Then in C#? The converter gave me if (oStruct.AH_DATE != 1/1/1900 12:00:00 AM) { which is of course not correct but I cannot seem to work out how to make it correct.

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• android app unable to connect to the hsqldb server

  - by Chinta

  I am trying to connect my android app to the hsql db server. Server runs on computer-1. I can connect to the db server from local machine through java as well as Db-visualizer. I can connect to the db server from another computer(computer-2) using Db-visualizer with comouter-1 ip address. Now trying to connect from my app in Nexus 7 the same way I was connecting from computer-2. I am getting "No Suitable Driver" error. Below is the log. 11-02 12:01:41.235: W/System.err(9803): connection string <jdbc:hsqldb:hsql://192.168.2.6:9001/qBank> 11-02 12:01:41.235: W/System.err(9803): user id string <SA> 11-02 12:01:41.235: W/System.err(9803): password string <> 11-02 12:01:41.235: W/System.err(9803): ERROR: failed to get connection. 11-02 12:01:41.235: W/System.err(9803): java.sql.SQLException: No suitable driver 11-02 12:01:41.235: W/System.err(9803): at java.sql.DriverManager.getConnection(DriverManager.java:186) 11-02 12:01:41.235: W/System.err(9803): at java.sql.DriverManager.getConnection(DriverManager.java:213) 11-02 12:01:41.235: W/System.err(9803): at com.scan.util.GatherData.getConnection(GatherData.java:135)

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• A programming language that does not allow IO. Haskell is not a pure language

  - by TheIronKnuckle

  (I asked this on Stack Overflow and it got closed as off-topic, I was a bit confused until I read the FAQ, which discouraged subjective theoratical debate style questions. The FAQ here doesn't seem to have a problem with it and it sounds like this is a more appropriate place to post. If this gets closed again, forgive me, I'm not trying to troll) Are there any 100% pure languages (as I describe in the Stack Overflow post) out there already and if so, could they feasibly be used to actually do stuff? i.e. do they have an implementation? I'm not looking for raw maths on paper/Pure lambda calculus. However Pure lambda calculus with a compiler or a runtime system attached is something I'd be interested in hearing about.

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• What are the benefits of archiving?

  - by HappyDeveloper

  I always see sites that only keeps fresh content on the home or subsections, and the rest of the content is kept in a separate section called 'archive'. Recently I have also heard that NoSQL DB's like MongoDB are good for archiving (which makes me think this is related to performance) So why do sites archive their content? What's the benefit over say, a simple paginator through which you could reach all the content? Is archiving done for performance? Or SEO? Or just user experience?

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• Is there a way to prevent others to steal your open source project and use it to make a profit?

  - by Jubbat

  This might seems like a silly question to ask, but I can't really figure out the answer. The title pretty much says it all. Let's say you have an open source music player, along comes someone, copies it, adds features, modifies the interface, etc and sells it. Nobody would find out. So how does it work? Related: I'm working in some projects myself to make me more employable, so employers can take a look at my code but with some of them I don't feel like uploading them to an online repository, ie sourceforge, and make them visible for the general public.

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• How to solve my big communication issue and take care in future

  - by Rahul Mehta

  My company had a POC which was done by me,my senior ,my boss and our channel partner team 4 people and our company team done most of coding and first installation of the softwares of the POC was done by channel partner team, and documented the same thing, i had installed on our server, Our comapny team worked very hard. Now we are about to start second stage of POC. But today my boss told me that my senior and channel partner team have issue with me ,regarding my communication. So before considering me on this project they want to resolve this issue or not considered me . I agree i have less communications skills. and I don't ask any question till i need to any one , i prefer to ask on stackoverflow. But i don't know, how this issue is being arise ,i had done all the things they asked , replied to all email and talk on phone. I always obeyed them. I always told them what they asked. what should i do that these type of issue doesn't arrive in future. And now boss told me to prepare a script to talk with my senior to resolve the issue. what should i talk to my senior? I want to work on this project , but i don't want to do so much request to work on this project. How should and what should (Code Documentation , Research Material I done etc . what are docs neccessary for communication with team member )i communication with my team member in future so these kind of issue not arise.

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• How do i rotate a 2D picturebox according to my mouse

  - by Gwenda.T

  I would want to rotate my picturebox which contains an image. The image will just spin around following the mouse, but the position of the image is fixed. Any idea on how it should be done? Btw using Visual Studio 2012 C# Windows phone application for Windows Phone 8. I've did a little research on google but the other codes were from VS2012 using a WinForm But it's different now I'm not able to use their code. So I was hoping I could find some answer at here! Currently now I have this private void arrowHead_Tap(object sender, System.Windows.Input.GestureEventArgs e) { Duration Time_duration = new Duration(TimeSpan.FromSeconds(0.5)); Storyboard MyStory = new Storyboard(); MyStory.Duration = Time_duration; DoubleAnimation My_Double = new DoubleAnimation(); My_Double.Duration = Time_duration; MyStory.Children.Add(My_Double); RotateTransform MyTransform = new RotateTransform(); Storyboard.SetTarget(My_Double, MyTransform); Storyboard.SetTargetProperty(My_Double, new PropertyPath("Angle")); My_Double.To = 15; arrowHead.RenderTransform = MyTransform; arrowHead.RenderTransformOrigin = new Point(0.5, 0.5); //stackPanel1.Children.Add(image1); MyStory.Begin(); } This is my only way of tilting the image however now I want it to follow my mouse! Thanks!

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• ERP/CRM Systems. Desktop Based ? Web based?

  - by Parhs

  Hello guys... I have seen 2-3 ERPs in action. I am wondering what is better. Desktop based application or webbased displayed on a browser. My first expirience was with a web based ERP when i was 14 years old.. It was web based and terribly slow... For most simple task you had to do lots of clicks... no keyboard support ..... Pages took ages to load. Last year i worked for migrating to a newer computer some old terminal based cobol application. The computer that worked till today and still has no problem was from 1993. The user interface ofcourse was textbased.. The speed that guys placed orders was amazing! just typing the name of the customer , then 5-10 keys to add a product to order.... Comparing to this ERP the page for placing orders Link (click sales orders) seems terribly slow to add a product... No keyboard shortcut works to save what you added and generally i believe you need 4 times more time to place an order compared to the text interface... Having to use both mouse and keyboard for this task is BAD and sadistic... So how can tek heck these people ever use a system like that ??? So in the long run desktop application seems the only way... Ofcourse browsers support shortcuts but the way to overide the defaults that browsers uses isnt cross compatible... That is a hudge problem. Finnaly, if we MUST/forced use cloud in near future what about keyboard shortcuts?? I feel confused... I have seen converters of desktop applications to browser applications but are SLOW as hell... The question is what about user friendliness?What kind of application would you use?

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• What is considered third party code?

  - by Songo

  Inspired by this question Using third-party libraries - always use a wrapper? I wanted to know what people actually consider as third-party libraries. Example from PHP: If I'm building an application using Zend framework, should I treat Zend framework libraries as third party code? Example from C#: If I'm building a desktop application, should I treat all .Net classes as third party code? Example from Java: Should I treat all libraries in the JDK as third party libraries? Some people say that if a library is stable and won't change often then one doesn't need to wrap it. However I fail to see how one would test a class that depends on a third party code without wrapping it.

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• How do I tell the cases when it's worth to use LINQ?

  - by Lijo

  Many things in LINQ can be accomplished without the library. But for some scenarios, LINQ is most appropriate. Examples are: SELECT - http://stackoverflow.com/questions/11883262/wrapping-list-items-inside-div-in-a-repeater SelectMany, Contains - http://stackoverflow.com/questions/11778979/better-code-pattern-for-checking-existence-of-value Enumerable.Range - http://stackoverflow.com/questions/11780128/scalable-c-sharp-code-for-creating-array-from-config-file WHERE http://stackoverflow.com/questions/13171850/trim-string-if-a-string-ends-with-a-specific-word What factors to take into account when deciding between LINQ and regular .Net language elements?

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• How can I discourage the use of Access?

  - by Greg Buehler

  Lets pretend that a very large company (revenue numbers with more than 8 figures) is looking to do a refresh on a software system, particularly the dashboard used by employees. This system was originally put together in the early 1990's to handle inventory tracking and storage across a variety of facilities (10+). Since this large company is now in the process of implementing some of these inventory processes with SAP they are in need of a major refresh. The existing system: Microsoft Access project performs dashboard duties Unique shipping/receiving configurations at different facilities require unique forms and queries within the Access project Uses 3rd party libraries referenced by Access to directly interface with at control system (read: motors, conveyors, and counters) Individual SQL Server 2000 instances (some traces of pre-update SQL Server 6.0 documents) at each facility The Issue: This system started as a home brewed inventory tracking scheme with a single internal sponsor who is still in charge of the technical direction. The original sponsor prescribing the desired deliverables that are being called for in the current RFP. The RFP describes a system based around a single Access project. Any suggestion that Access is ill suited for a project of this scope are shot down under the reasoning that "it works for the scope now". Are there any case studies, notices, or statements that can be used to disuade this potential customer from repeating their mistake? Does Microsoft make any statements directly about when it is highly recommended to ditch Access?

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• Pattern for a class that does only one thing

  - by Heinzi

  Let's say I have a procedure that does stuff: void doStuff(initalParams) { ... } Now I discover that "doing stuff" is quite a compex operation. The procedure becomes large, I split it up into multiple smaller procedures and soon I realize that having some kind of state would be useful while doing stuff, so that I need to pass less parameters between the small procedures. So, I factor it out into its own class: class StuffDoer { private someInternalState; public Start(initalParams) { ... } // some private helper procedures here ... } And then I call it like this: new StuffDoer().Start(initialParams); or like this: new StuffDoer(initialParams).Start(); And this is what feels wrong. When using the .NET or Java API, I always never call new SomeApiClass().Start(...);, which makes me suspect that I'm doing it wrong. Sure, I could make StuffDoer's constructor private and add a static helper method: public static DoStuff(initalParams) { new StuffDoer().Start(initialParams); } But then I'd have a class whose external interface consists of only one static method, which also feels weird. Hence my question: Is there a well-established pattern for this type of classes that have only one entry point and have no "externally recognizable" state, i.e., instance state is only required during execution of that one entry point?

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• MIT and copyright

  - by Petah

  I am contributing to a library that is licensed under the MIT license. In the license and in each class file it has a comment at the top saying: Copyright (c) 2011 Joe Bloggs <[email protected]> I assume that he owns the copyright to the file, and can change the license of that file as he sees fit. If I contribute to the library with a new class entirely write by me, can I claim copyright of that file. And put: Copyright (c) 2011 Petah Piper <[email protected]> at the top?

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• Should custom data elements be stored as XML or database entries?

  - by meteorainer

  There are a ton of questions like this, but they are mostly very generalized, so I'd like to get some views on my specific usage. General: I'm building a new project on my own in Django. It's focus will be on small businesses. I'd like to make it somewhat customizble for my clients so they can add to their customer/invoice/employee/whatever items. My models would reflect boilerplate items that all ModelX might have. For example: first name last name email address ... Then my user's would be able to add fields for whatever data they might like. I'm still in design phase and am building this myself, so I've got some options. Working on... Right now the 'extra items' models have a FK to the generic model (Customer and CustomerDataPoints for example). All values in the extra data points are stored as char and will be coerced/parced into their actual format at view building. In this build the user could theoretically add whatever values they want, group them in sets and generally access them at will from the views relavent to that model. Pros: Low storage overhead, very extensible, searchable Cons: More sql joins My other option is to use some type of markup, or key-value pairing stored directly onto the boilerplate models. This coul essentially just be any low-overhead method weather XML or literal strings. The view and form generated from the stored data would be taking control of validation and reoganizing on updates. Then it would just dump the data back in as a char/blob/whatever. Something like: <datapoint type='char' value='something' required='true' /> <datapoint type='date' value='01/01/2001' required='false' /> ... Pros: No joins needed, Updates for validation and views are decoupled from data Cons: Much higher storage overhead, limited capacity to search on extra content So my question is: If you didn't live in the contraints impose by your company what method would you use? Why? What benefits or pitfalls do you see down the road for me as a small business trying to help other small businesses? Just to clarify, I am not asking about custom UI elements, those I can handle with forms and template snippets. I'm asking primarily about data storage and retreival of non standardized data relative to a boilerplate model.

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• Algorithm to reduce calls to mapping API

  - by aidan

  A random distribution of points lies on a map. This data lies behind an API, and I want to grab the complete set of points within a given bounding box. I can query the API with the bounding box and the API will return the set of points that fall within that box. The problem is that the API will limit the result set to 10 items, with no pagination and no indication if there are more points that have been omitted. So I made a recursive algorithm that takes a bounding box and requests the points that lie within it. If the result set is exactly 10 items, then I split the bounding box into four quadrants and recurse. It works fine but my question is this: if want to minimize the number of API calls, what is the optimal way to split the bounding box? Splitting it into quadrants was just an arbitrary decision. When there are a lot of points on the map, I have to drill down many levels before I start getting meaningful results. So I imagine it might be faster to split the box into, say, 9, 16, or more sections. But if I do that, then I eventually get to a point where a lot of requests are returning 0 results which isn't so efficient. Also, does the size of the limit on the results set affect the answer? (This is all assuming that I have no prior knowledge of nominal point density in the bounding box)

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• What programming language was used to develop Windows OS?

  - by nardo

  I am very new to programming and I have started to learn programming just last week. I am still having trouble understanding about programming languages, especially what to use in a particular system. My first language is Java and it's the only programming language I have experience with. I know there are a lot of programming languages out there but I am so curious what programming language was used to develop Windows? Can Java be used to develop an OS?

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