Basics
The Ximian Role in the Mono project
Mono and GNOME
Building GUI applications with Mono
Mono and Microsoft
Mono and the Portable.NET Project
Web Services
Mono and ASP.NET
Mono and ADO.NET
Development Tools and Issues
Mono and Java
Extending Mono
Portability
Reusing Existing Code
Mono and GCC
Performance
Licensing
Patents
Miscellaneous Questions
Mono Common Problems
A Spanish translation is also available ** Basics Q: What is Mono exactly? A: The Mono Project is an open development initiative sponsored by Ximian that is working to develop an open source, Unix version of the Microsoft .NET development platform. Its objective is to enable Unix developers to build and deploy cross-platform .NET Applications. The project will implement various technologies developed by Microsoft that have now been submitted to the ECMA for standardization. Q: What is the difference between Mono and the .NET Initiative? A: The ".NET Initiative" is a somewhat nebulous company-wide effort by Microsoft, one part of which is a cross-platform development framework. Mono is an implementation of the development framework, but not an implementation of anything else related to the .NET Initiative, such as Passport, software-as-a-service, or corporate re-branding. Q: What technologies are included in Mono? A: Mono contains a number of components useful for building new software: Windows has compilers that target the virtual machine from a number of languages: Managed C++, Java Script, Eiffel, Component Pascal, APL, Cobol, Perl, Python, Scheme, Smalltalk, Standard ML, Haskell, Mercury and Oberon. The CLR and the Common Type System (CTS) enables applications and libraries to be written in a collection of different languages that target the byte code This means for example that if you define a class to do algebraic manipulation in C#, that class can be reused from any other language that supports the CLI. You could create a class in C#, subclass it in C++ and instantiate it in an Eiffel program. A single object system, threading system, class libraries, and garbage collection system can be shared across all these languages. Q: Where can I find the specification for these technologies? A: You can find the information here: C# http://www.ecma.ch/ecma1/STAND/ecma-334.htm CLI http://www.ecma.ch/ecma1/STAND/ecma-335.htm Q: Will you implement the .NET Framework SDK class libraries? A: Yes, we will be implementing the APIs of the .NET Framework SDK class libraries. Q: Will you offer an ECMA-compliant set of class libraries? A: Eventually we will. Our current focus is on inter-operating with the Microsoft SDK, but we will also offer an ECMA compliant set of libraries. Q: What does the name "Mono" mean? A: Mono is the word for `monkey' in Spanish. We like monkeys. Q: Is Mono usable? A: The JIT engine is usable on Intel x86 machines. An interpreter can be used on other non-Intel x86 machines. The class libraries are mature enough to run some real applications (the compiler for instance, and every day more and more applications are natively developed with Mono). Q: When will you ship it? A: Different parts of Mono will achieve usability at different stages, once we are comfortable with the compiler, we will release "Mono Core", which contains everything needed to develop applications with the base class libraries. This should be available at some point during 2002. Other higher level class libraries (ASP.NET, ADO.NET) will be released when they become stable. Q: What major components will you include in Mono? A: Hopefully everything that Microsoft ships on their Framework (ADO.NET, ASP.NET), and we encourage third party developers to create reusable components that work on both Mono and Windows. Q: How can I contribute? A: Check the contributing section. Q: Aren't you just copying someone else's work? A: We are interested in providing the best tools for programmers to develop applications for Free Operating Systems. We also want to help provide the interoperability that will allow those systems to fit in with other standards. For more background, read the Mono Project white paper. the project. Q: Miguel said once that Mono was being implemented in COBOL. Is that true?. A: No. It was a joke. ** The Ximian Role in the Mono Project Q: Why is Ximian working on .NET? A: Ximian is interested in providing the best tools for programmers to develop applications for Free Operating Systems. For more information, read the project rationale page. Q: Will Ximian be able to take on a project of this size? A: Of course not. Ximian a supporter of the Mono project, but the only way to implement something of this size is for the entire free software community to get involved. Visit the contributing page if you'd like to help out. Q: What pieces will Ximian be working on? A: We will devote most of our resources to work on the pieces which are on the critical path to release a development and execution environment. Once the project is at a stage where it is useful in the real world, it will achieve a critical mass of developers to improve it further. Q: Will Ximian offer Mono commercially? A: When Mono is ready to be shipped Ximian will offer a commercial support and services for Mono. Q: Does Ximian provide consulting services around Mono? A: Yes, Ximian does provide consulting services around Mono to make it suitable to your needs. Porting the runtime engine, customizing it, working on specific classes or tuning the code for your particular needs. Q: Will you wait until Mono is finished? A: Mono will ship on various stages as they mature. Some people require only a subset of the technologies, those will ship first. More advanced features will take more time to develop. A support time line will be available in June 2002. ** Mono and GNOME Q: How is Mono related to GNOME? A: In a number of ways. This project was born out of the need of providing improved tools for the GNOME community, and will use existing components that have been developed for GNOME when they are available. For example, we plan to use Gtk+ and Libart to implement Winforms and the Drawing2D API and are considering GObject support. Q: Has the GNOME Foundation or the GNOME team adopted Mono? A: Mono is too new to be adopted by those groups. We hope that the tools that we will provide will be adopted by free software programmers including the GNOME Foundation members and the GNOME project generally. Q: Should GNOME programmers switch over to Mono now? A: It is still far to early for discussions of "switching over." No pieces of Mono will be ready within the next six months, and a complete implementation is roughly one year away. We encourage GNOME developers to continue using the existing tools, libraries and components. Improvements made to GNOME will have an impact on Mono, as they would be the "back-end" for various classes. Q: Will Mono include compatibility with Bonobo components? What is the relationship between Mono and Bonobo? A: Yes, we will provide a set of classes for implementing and using Bonobo components from within Mono. Mono should allow you to write Bonobo components more easily, just like .NET on Windows allows you to export .NET components to COM. Q: Does Mono depend on GNOME? A: No, Mono does not depend on GNOME. We use a few packages produced by the GNOME team like the `glib' library. Q: But will I be able to build GNOME applications? A: Yes, we will enable people to write GNOME applications using Mono. Q: Do you have C# bindings for GNOME?. A: Yes, we currently bind libgnome, libgnomecanvas, and libgnomeui -- although I dare say I have no idea how functional the bindings are outside of what I tested in the sample app. I imagine other libraries under the GNOME framework will be added on an as-needed (and as-requested) basis...although a truly good bonobo binding will have to wait on the CORBA remoting support which has been started recently. ** GUI applications Q: Will Mono enable GUI applications to be authored? A: Yes, you will be able to build GUI applications. Indeed, that is our main focus. We will provide both the Windows.Forms API and the Gtk# API. Q: What is the difference between Gtk# and System.Windows.Forms? A: Gtk# is a set of bindings for the Gtk+ toolkit for C# (and other CIL-enabled languages). System.Windows.Forms is an API defined by Microsoft to build GUI applications. Q: Will I be able to run my smart clients on systems powered by Mono? A: As long as your applications are 100% .NET and do not make use of P/Invoke to call Win32 functions, your smart client applications will run on Mono platforms. Q: Where can I learn more about Gtk#? A: The following ** Mono and Microsoft Q: Is Microsoft helping Ximian with this project? A: No. Ximian CTO Miguel de Icaza had a friendly conversation with Microsoft software architect David Stutz, but that's about the extent of the contact. Microsoft is interested in other implementations of .NET and are willing to help make the ECMA spec more accurate for this purpose. Ximian representatives have also spoken with Sam Ruby at the ECMA TG3 committee to discuss the same issues. Q: Is Microsoft or Corel paying Ximian to do this? A: No. Q: Do you fear that Microsoft will change the spec and render Mono useless? A: No. Microsoft proved with the CLI and the C# language that it was possible to create a powerful foundation for many languages to inter-operate. We will always have that. Even if changes happened in the platform which were undocumented, the existing platform would a value on its own. Q: Are you writing Mono from the ECMA specs? A: Yes, we are writing them from the ECMA specs and the published materials in print about .NET. Q: If my applications use Mono, will I have to pay a service fee? A: No. Mono is not related to Microsoft's initiative of software-as-a-service. Q: Is the Mono Project is related to the Microsoft Hailstorm effort? Is Ximian endorsing Hailstorm? A: No. The Mono Project is focused on providing a compatible set of tools for the Microsoft .NET development platform. It does not address, require, or otherwise endorse the MS Passport-based Hailstorm single sign-on system that is part of Windows XP and other services. Q: Will Mono or .NET applications depend on Microsoft Passport? A: No. MS Passport is unrelated to running .NET compatible applications produced with the Mono tools. The only thing you will need is a just-in-time compiler (JIT). Q: What is a 100% .NET application? A: A `100% .NET application' is one that only uses the APIs defined under the System namespace and does not use PInvoke. These applications would in theory run unmodified on Windows, Linux, HP-UX, Solaris, MacOS X and others. Q: If Microsoft will release a port of their .NET platform under the `Shared Source' license, why should I bother with anything else? A: The Shared Source implementation will be expensive and its uses will be tightly restricted, especially for commercial use. We are working towards an implementation that will grant a number of important rights to recipients: use for any purpose, redistribution, modification, and redistribution of modifications. This is what we call Free Software Q: Is Mono a free implementation of Passport? A: No. Mono is just a runtime, a compiler and a set of class libraries. Q: Will the System.Web.Security.PassportIdentity class mean that my software will depend on Passport? A: No. Applications may use that API to contact a Passport site, but are not required to do so. As long as your application does not use Passport, you will not need Passport. Q: Will Mono running on Linux make Passport available for Linux? A: No. However, the Passport toolkit for Linux-based web servers is available from Microsoft. Q: Will Mono allow me to run Microsoft Office on Linux? A: No, it will not. Microsoft Office is a Windows application. To learn more about running Windows applications on Intel Unix systems refer to the Wine Project. Q: Will I be able to compile a Microsoft VB.NET application and execute the resultant MSIL file under MONO on Linux without converting to C# and recompiling? A: Once we have a complete VisualBasic runtime, yes. Q: Can mono run the WebMatrix? A: No. That requires System.Windows.Forms support which is not currently implemented. Q: Does mono have something like Passport? Will mono have a server side Passport/Similar framework for XSP as well as client classes? A: Not yet, but the client side API for authentication is not the problem. We will likely have a lot of other authentication APIs, like the Liberty Alliance APIs. The problem is people on the web provider end that might use this for authentication. ** Mono and Portable.NET Q: What are the differences between Mono and Portable.NET? A: Most of Mono is being written using C#, with only a few parts written in C (The JIT engine, the runtime, the interfaces to the garbage collection system). It is easier to describe what is unique about Mono: ** Web Services Q: How is Mono related to Web Services? A: Mono is only related to Web Services in that it will implement the same set of classes that have been authored in the .NET Framework to simplify and streamline the process of building Web Services. But most importantly, Mono is an Open Source implementation of the .NET Framework. Q: Can I author Web Services with Mono? A: You will be able to write Web Services on .NET that run on Mono and vice-versa. Q: If Mono implements the SDK classes, will I be able to write and execute .NET Web Services with it? A: Yes. When the project is finished, you will be able to use the same technologies that are available through the .NET Framework SDK on Windows to write Web Services. Q: What about Soup? Can I use Soup without Mono? A: Soup is a library for GNOME applications to create SOAP servers and SOAP clients, and can be used without Mono. You can browse the source code for soup using GNOME's Bonsai. Q: Can I use CORBA? A: Yes. The CLI contains enough information about a class that exposing it to other RPC systems (like CORBA) is really simple, and does not even require support from an object. We will be implementing CORBA inter-operation as an extension to the Mono classes so that we can integrate with Bonobo, just like Microsoft provides COM inter-operation classes and support mechanisms. Q: Can I serialize my objects to other things other than XML? A: Yes, although the serializing tools have not yet been planned, and you would probably have to implement them yourself. Q: Will Mono use ORBit? A: No. Mono will be using a new implementation of CORBA that isn't still started. ** Development Tools and Issues Q: Will it be possible to use the CLI features without using byte codes or the JIT? A: Yes. The CLI engine will be made available as a shared library. The garbage collection engine, the threading abstraction, the object system, the dynamic type code system and the JIT will be available for C developers to integrate with their applications if they wish to do so. Q: Will you have new development tools? A: With any luck, Free Software enthusiasts will contribute tools to improve the developer environment. These tools could be developed initially using the Microsoft implementation of the CLI and then executed later with Mono. Q: What kind of rules make the Common Intermediate Language useful for JITers? A: The main rule is that the stack in the CLI is not a general purpose stack. You are not allowed to use it for other purposes than computing values and passing arguments to functions or return values. At any given call or return instruction, the types on the stack have to be the same independently of the flow of execution of your code. Q: Is it true that the CIL is ideal for JITing and not efficient for interpreters? A: The CIL is better suited to be JITed than JVM byte codes, but you can interpret them as trivially as you can interpret JVM byte codes. Q: Isn't it a little bit confusing to have the name of "XSP" (the same as in the Apache Project) for the ASP.NET support in Mono?. A: In Mono, xsp is just the name of the C# code generator for ASP.NET pages. In the Apache Project, it is a term for the "eXtensible Server Pages" technology so as they are very different things, they don't conflict. Q: What about using something like Jabber instead of the System.Messaging namespace?. A: In short, MSMQ is not something like Jabber, but asynchronous messaging through queues. Useful queues do more than serialize messages, they are also platform bridges. Q: Are you supporting XMLDocument and relatives?. A: Currently, we aren't implementing them yet. It would require updates to most of the XmlNode derivatives so it's not a trivial task. We are currently focusing on getting XPath support working. Q: Is there any plan to develop an aspx server for Mono?. A: The web server turned out to be very simple compared to the rest of the work. Gonzalo has got the page generator mostly done (a module called xsp, who has nothing to do with the XSP term used in the Apache Project). Patrik has done a lot of the work to get the ProcessRequest to work. You can try to help in the final touches to the System.Web classes and writing regression tests for the widgets we have. Q: Is there any way I can develop the class libraries using Linux yet? A: Yes. Some class libraries can be developed on Linux. Search for Paolo's post (he lists which classes can be compiled fine now). Q: Is there any way I can install a known working copy of mono in /usr, and an experimental copy somewhere else, and have both copies use their own libraries? (I'm still not very good at library paths in Linux) A: Yes. Just use two installation prefixes. Q: How should I write tests or a tests suite? A: If you do a test suite for C#, you might want to keep it independent of the Mono C# compiler, so that other compiler implementations can later use it. Q: Would it be too terrible to have another corlib signed as mscorlib? A: We rename corlib to mscorlib also when saving the PE files, in fact, the runtime can execute program created by mono just fine. Q: Is there a relatively straightforward way to repeat the steps taken by Paolo to get Mono completely self-hosted on Linux? A: To build the compiler and class libraries in Linux, run: If you want to produce and distribute a monocharge tarball, run: make -f makefile.gnu dist Of course you have to run these in the top level mcs directory. Q: Is it possible to build a C# file to some sort of intermediate format which can linked into a final module, like the traditional .c -> .o -> .so path? A: You could do: mcs /target:module file1.cs, mcs /target:module file2.cs, mcs /target:exe file1.dll file2.dll /out:mybin.exe Q: Is there any plans for implementing remoting in the near future?, When will work in System.Runtime.Remoting.dll start? A: The remoting infrastructure is in place. Some of the channels and formatters are not. Q: I'm wondering if there are any plans to start using nant to build the class lib + test lib. i think that every project need/should use an automated build process and nant + a couple of tools enables this. is the problem that the compiler can't run nant yet? A: Maybe well be doing some sort of automated build process + testing when the summer finish. ** Mono and ASP.NET Q: Is Mono supporting ASP.NET? A: Yes. The development of the support for ASP.NET comes in various stages, here is what Gonzalo has been working on: 1. The Parser. 2. Getting the parser to generate output compatible with ASP.NET. 3. Running the sample output with the real Microsoft runtime but using our generated page. 4. Running the sample with our classes with the .NET runtime. 5. Running our sample code with our classes with our runtime. This is the process we are following. Currently Gonzalo has reached point 5. Q: Do I need install cygwin to work on ASP.NET in mono or Linux is enough since it is self host right now. A: Linux is enough. Q: Any plan to make ASP.NET in mono works with Apache in Linux?. A: Yes, we have plans to do so, but we need to wait for Patrik's patches to HttpRuntime. Once that is there, writing a mod_mono should be trivial (look at mono/samples/embed for a sample embedded application). ** Mono and ADO.NET Q: What is the status of ADO.NET support?. Could I start migrating applications from MS.NET to Mono?. A: You could start right now using the ADO.NET support in mono, of course, if you want to help filling the missing gaps while you develop your app :-) Well, what I mean is that we're not that far to having full ADO.NET support in Mono, and we've got a lot of working things, so if we could get more help, we'd finish it really soon :-) Q: In developing the data architecture for the application are there and objects I should stay away from in order to insure the smoothest possible transition (minimum code rewrite) to Mono's ADO.NET implementation? (For example, strongly typed datasets versus untyped datasets, etc...) A: We are implementing all the classes in Microsoft .NET's System.Data, so you can be sure that things will work the same in Mono as with the Microsoft implementation. ** Mono and Java Q: Why don't you use Java? After all, there are many languages that target the Java VM. A: You can get very good tools for doing Java development on free systems right now. Red Hat has contributed a GCC front-end for Java that can take Java sources or Java byte codes and generate native executables; Transvirtual has implemented Kaffe a JIT engine for Java; Intel also has a Java VM called ORP. The JVM is not designed to be a general purpose virtual machine. The Common Intermediate Language (CIL), on the other hand, is designed to be a target for a wide variety of programming languages, and has a set of rules designed to be optimal for JITers. Q: Could Java target the CLI? A: Yes, Java could target the CLI. We have details on a project that someone could take on to make this happen. Microsoft has an implementation of the Java language called J# that can target the CIL execution engine. Q: Is it possible to write a JVM byte code to CIL converter? A: Yes, it is possible. Here are a few starting point: Q: Could mono become a hybrid CIL/java platform? A: No. It is quite far from the philosophy of the project. The idea of Mono is, to have only _one_ VM, on which all can run. And if there existing a binary-converter from Java-.class to IL and if there existing something like J-Sharp on Mono, you can write programs in Java, which than can run on Mono. You do not need two bindings (like your example: GTK-Sharp _and_ Java-Gnome). You need only _one_ of it (GTK-Sharp). Thats the idea of Mono. An other point is, that there are no people, who use Open Source-JVMs. They all prefer Suns original. But for Unix there don't exist a .NET-Framework. So it is possible, that in the future Mono is the standard .NET for Unixes. Q: Do you plan to implement a Javascript compiler? A: Yes. Eto Demerzal has started a Rhino port to C#. After this is completed, we will begin developing the JavaScript compiler. ** Extending Mono Q: Would you allow other classes other than those in the specification? A: Yes. The Microsoft class collection is very big, but it is by no means complete. It would be nice to have a port of `Camel' (the Mail API used by Evolution inspired by Java Mail) for Mono applications. You might also want to look into implementing CORBA for Mono. Not only because it would be useful, but because it sounds like a fun thing to do, given the fact that the CLI is such a type rich system. For more information on extending Mono, see our ideas page. Q: Do you plan to Embrace and Extend .NET? A: Embracing a good technology is good. Extending technologies in incompatible ways is bad for the users, so we do not plan on extending the technologies. If you have innovative ideas, and want to create new classes, we encourage you to make those classes operate correctly well in both Mono and .NET. Q: Is there any way I can develop the class libraries using Linux yet? A: Yes. Some class libraries can be developed on Linux. Search for Paolo's post (he lists which classes can be compiled fine now). Q: Is there any way I can install a known working copy of mono in /usr, and an experimental copy somewhere else, and have both copies use their own libraries? (I'm still not very good at library paths in Linux) A: Yes. Just use two installation prefixes. ** Portability Q: Will Mono only work on Linux? A: Currently, we are doing our work on Linux-based systems and Windows. We do not expect many Linux-isms in the code, so it should be easy to port Mono to other UNIX variants. Q: What about Mono on non Linux-based systems? A: Our main intention at Ximian is to be able to develop GNOME applications with Mono, but if you are interested in providing a port of the Winforms classes to other platforms (frame buffer or MacOS X for example), we would gladly integrate them, as long they are under an open source license. Q: What operating systems/CPUs do you support A: Mono currently runs on Linux, Windows, Solaris and FreeBSD. There is a JIT engine available for x86 processors that can generate code and optimizations tailored for a particular CPU. Interpreters exist for the SPARC, PowerPC and StrongARM CPUs. Q: Does Mono run on Windows? A: Yes. You can get pre-compiled binaries from http://www.go-mono.com/download.html Q: Does Mono run on Linux? A: Yes. You can get pre-compiled binaries from http://www.go-mono.com/download.html Q: Will I require Cygwin to run mono? A: No. Cygwin is only required to build Mono. Q: Will Mono depend on GNOME? A: It will depend only if you are using a particular assembly (for example, for doing GUI applications). If you are just interested in Mono for implementing a `Hello World Enterprise P2P Web Service', you will not need any GNOME components. Q: Is anyone working on porting Mono to IA-64? A: Nobody is working on such port. Q: If I were about to start a Mono port to IA-64,would the same lburg code generator work for IA-64 also? or anything else need to be used for code generation(as the processor architecture is totally different from IA32) A: The lburg approach can be use for any processor architecture. But you might think in another better approach. Q: Do you plan to port Rhino to C#?. A: Eto Demerzal has started a Rhino port to C#. Q: Has anyone succeeded in building a Mac version of the C# environment. If so can you explain how? A: You could try to check with the Darwin people, or the Fink people. Mono/C# is self hosting on Linux/PPC which is the hard part, so it should be relatively simple to get it to work on MacOS ** Reusing Existing Code Q: What projects will you reuse or build upon? A: We want to get Mono in the hands of programmers soon. We are interested in reusing existing open source software. Q: What about Intel's research JIT framework, ORP? A: At this time, we are investigating whether we can use elements of ORP for Mono. ORP is a research JIT engine that has a clearly defined API that splits the JIT from the GC system and the actual byte code implementation. We are using some pieces of ORP (Their code generation interface) and we use it as a source of inspiration for optimizations. Paolo and Dietmar consider ORP as being one of the best JIT engines out there (and their research work and papers are very useful if you are interested in JIT technology). Q: What about using GNU Lightning? A: We are not using GNU Lightning. Our JIT is using an instruction selector based on tree-pattern matching, and a code generation interface that is very tied to the current architecture. Q: Will I be able to use Microsoft SQL Server 2000 or will I need to switch to a specific Open Source Database. Will I need to recode? A: There should not be any need to recode. Q: What do I need to watch out for when programming in VB.NET so that I'm sure to be able to run those apps on Linux? A: Not making any PInvoke or DLL calls should and not using anything in the Microsoft.* namespaces should suffice. Also do not use any Methods/Classes marked as "This type/method supports the .NET Framework infrastructure and is not intended to be used directly from your code." even if you know what these classes/methods do. Q: Will built-in reporting be supported for crystal reports? This is a heavily used part of our system. A: Probably not. Crystal Reports are propriety. Someone may try to emulate the behavior, but no-one has yet volunteered. Q: Who about writing to the registry? As I understand it, Linux does not have a counterpart to the registry. Should I avoid relying on that feature? A: Try to avoid it. Although there would be a emulation for registry in Mono too. GNOME does have a registry like mechanism for configuration. But Even if gnome has a configuration system similar to the registry, the keys will not be equal, so you will probably end up having to do some runtime detection, and depending on this load an assembly that has your platform-specific hacks. Q: System.Data.SqlClient with FreeTDS, will you port parts of these to C# and use them? A: if their license is compatible with mono's, yes, we'd think about porting them. If not, we'll continue with the plan of using FreeTDS. ** Mono and GCC Q: Are you working on a GCC front-end to C#? A GCC back-end that will generate CIL images? What about making a front-end to GCC that takes CIL images and generates native code? A: We are currently seeking volunteers for those projects. Visit the contributing section if you are interested. Q: But would this work around the GPL in the GCC compiler and allow people to work on non-free front-ends? A: People can already do this by targeting the JVM byte codes (there are about 130 compilers for various languages that target the JVM). Q: Why are you writing a JIT engine instead of a front-end to GCC? A: We want the JIT engine and runtime engine because they will be able to execute CIL executables generated on Windows, and so no recompilation will be necessary. ** Performance Q: How fast will Mono be? A: We can not predict the future, but a conservative estimate is that it would be at least `as fast as other JIT engines'. We would like to ship various JIT engines with Mono, just like Microsoft has done with their .NET development platform. We could provide a faster, JIT for fast load times but lower performance, and an and an optimizing JIT that would be slower at generating code but produce more optimal output. The CIL has some advantages over the Java byte code: it is really an intermediate representation and there are a number of restrictions on how you can emit CIL code that simplify creating better JIT engines. For example, on the CIL, the stack is not really an abstraction available for the code generator to use at will. Rather, it is a way of creating a postfix representation of the parsed tree. At any given call point or return point, the contents of the stack are expected to contain the same object types independently of how the instruction was reached. ** Licensing Q: Will I be able to write proprietary applications that run with Mono? A: Yes. The licensing scheme is planned to allow proprietary developers to write applications with Mono. Q: What license or licenses are you using for the Mono Project? A: The C# Compiler is released under the terms of the GNU GPL. The runtime libraries are under the GNU Library GPL. And the class libraries are released under the terms of the MIT X11 license. The Mono runtime and the Mono C# Compiler are also available under a proprietary license for those who can not use the LGPL and the GPL in their code. For licensing details, contact mono-licensing@ximian.com Q: I would like to contribute code to Mono under a particular license. What licenses will you accept? A: We will have to evaluate the licenses for compatibility first, but as a general rule, we will accept the code under the same terms of the "container" module. Q: Is the Mono ** Patents Q: Could patents be used to completely disable Mono (either submarine patents filed now, or changes made by Microsoft specifically to create patent problems)? A: No. First, its basic functional capabilities have pre-existed too long to be held up by patents. The basic components of Mono are technologically equivalent to Sun's Java technology, which has been around for years. Mono will also implement multi-language and multi-architecture support, but there are previous technologies such as UCSD p-code and ANDF that also support multiple languages using a common intermediate language. The libraries are similar to other language's libraries, so again, they're too similar to be patentable in large measure. However, if Microsoft does patent some technology, then our plan is to either (1) work around it, (2) chop out patented pieces, (3) find prior art that would render the patent useless. Not providing a patented capability would weaken the interoperability, but it would still provide the free software / open source software community with good development tools, which is the primary reason for developing Mono. ** Miscellaneous Questions Q: You say that the CLI allows multiple languages to execute on the same environment. Isn't this the purpose of CORBA? A: The key difference between CORBA (and COM) and the CLI is that the CLI allows "data-level interoperability" because every language/component uses the same data layout and memory management. This means you can operate directly upon the data types that someone else provides, without having to go via their interfaces. It also means you don't have to "marshal" (convert) parameters (data layouts are the same, so you can just pass components directly) and you don't have to worry about memory management, because all languages/components share the same garbage collector and address space. This means much less copying and no need for reference counting. Q: Will you support COM? A: The runtime will support XPCOM on Unix systems and COM on Windows. Most of the code for dynamic trampolines exists already. Q: Will Ximian offer certifications on Mono or related technologies?. A: It's possible. But there is no plan about this. So the short answer is no. Q: Are there any Boehm's GC binaries? A: Yes. You can find RPMs here, though if your distribution provides the correct packages, you should use those. The suggested version of the Boehm GC is 6.1. Q: How can I report a bug? A: The best thing is to track down the bug and provide a simple test to reproduce the bug. You can then add the bug to the bugtracking system. Please provide information about what version of mono you're using and any relevant details to be able to reproduce the bug. Note that bugs reported on the mailing-list may be easily forgotten, so it's better to file them in the bug tracking system. Q: Does mcs support the same command line options as the MS C# compiler? A: The Mono C# compiler now supports the same command line arguments as the Microsoft C# compiler does. Q: How about getting searchable archives on lists.ximian.com? A: You can perform a search on the mono-related mailing lists here. Q: When using mono from cvs or from a snapshot, I get an error messaage saying that Mono and the runtime are out of sync. How do I fix that? A: If you use mono from cvs, you need to be prepared for changes in the runtime internals. This means that you should keep a working setup before blindling updating (a working setup may just be the last released tarball or a recent binary snapshot). Usually, compiling corlib with mcs before recompiling the C runtime does the right thing (but occasionally you may need to do it the other way around). ** Mono Common Problems If you are having problems compiling or running Mono software or if you think that you found a bug, etc. Please visit the Mono Common Problems document and try there.