3 Q: What is Mono exactly?
5 A: The Mono Project is a community initiative to develop an open
6 source, Linux-based version of the Microsoft.NET development
7 platform. Its objective is to enable Linux developers to build and
8 deploy cross platform .NET Applications. The project will
9 implement various technologies developed by Microsoft that have now
10 been submitted to the ECMA for standardization.
12 Q: Is Mono a .NET implementation?
14 A: No. Microsoft.Net is a broad, company-wide effort that ranges from
15 development tools to end user applications. Some components of
16 this initiative have been announced and some others are in the
20 Q: What technologies are included in Mono?
22 A: Mono contains a number of components useful for building new
26 * A Common Language Infrastructure (CLI) virtual
27 machine that contains a class loader, Just-in-time
28 compiler, and a garbage collecting runtime.
30 * A class library that can work with any language
31 which works on the CLR.
33 * A compiler for the C# language. In the future we
34 might work on other compilers that target the Common
41 Windows has compilers that target the virtual machine from <a
42 href="http://msdn.microsoft.com/net/thirdparty/default.asp#lang">a
43 number of languages:</a> Managed C++, Java Script, Eiffel,
44 Component Pascal, APL, Cobol, Oberon, Perl, Python, Scheme,
45 Smalltalk, Standard ML, Haskell, Mercury and Oberon.
47 The CLR and the Common Type System (CTS) enables applications and
48 libraries to be written in a collection of different languages that
51 This means for example that if you define a class to do algebraic
52 manipulation in C#, that class can be reused from any other
53 language that supports the CLI. You could create a class in C#,
54 subclass it in C++ and instantiate it in an Eiffel program.
56 A single object system, threading system, class libraries, and
57 garbage collection system can be shared across all these languages.
59 Q: Where can I find the specification for these technologies?
61 A: You can find the work-in-progress documentation from the T3G ECMA
64 <a href="http://www.dotnetexperts.com">http://www.dotnetexperts.com</a>
66 Q: Will you implement the .NET Framework SDK class libraries?
68 A: Yes, we will be implementing the APIs of the .NET Framework SDK
71 Q: What does Mono stand for?
73 A: Mono is the word for `Monkey' in Spanish. We like monkeys.
75 It only means a number of other things: monochromatic (hence the
76 gray theme used in the Web site).
78 Q: When will you ship it?
80 A: It is premature to target a shipdate for the code. While we anticipate
81 availability in the middle of next year, the more contributions we
82 get to the project, the sooner it will ship.
84 Q: How can I contribute?
86 A: Check the <a href="contributing.html">contributing</a> section.
88 Q: Aren't you just copying someone else's work?
90 A: We are interested in providing the best tools for programmers to
91 develop applications for Free Operating Systems. We also want to help
92 provide the interoperability that will allow those systems to fit in
95 Please read the <a href="http://www.go-mono.com/rationale.html">Mono
96 Project white paper</a> on Ximian site] for more background and the
97 rationale for the project.
99 ** The Ximian role in the Mono Project
101 Q: Why is Ximian working on .NET?
103 A: We are interested in providing the best tools for programmers to
104 develop applications for Free Operating Systems.
106 For more information, read the project <a
107 href="rationale.html">rationale</a> page.
109 Q: Will Ximian be able to take on a project of this size?
111 A: Ximian cannot and will not be able to take on the whole project on
112 its own. Ximian is spearheading the effort and providing a call to
113 action. Mono will be a free software/open source community
114 project; that is the only way to implement something of this
115 size. Visit the <a href="contributing.html">contributing</a> page
116 on this site to learn more about what you can do.
118 Q: What pieces will Ximian be working on?
120 A: We will devote most of our resources to work on the pieces which are
121 on the critical path to release a development and execution environment.
123 The idea is to get Mono to a state of that would allow
124 third parties to actually be able to use it real-world development.
127 ** Relationship with GNOME
129 Q: How is this related to GNOME?
131 A: In a number of ways. This project was born out of the need of
132 providing improved tools for the GNOME community, and will use
133 existing components that have been developed for GNOME when they
134 are available. For example, we plan to use Gtk+ and Libart to
135 implement Winforms and the Drawing2D API and are considering
138 Q: Has the GNOME Foundation or the GNOME team adopted Mono?
140 A: Mono is too new to be adopted by those groups. We hope that the
141 tools that we will provide will be adopted by free software
142 programmers including the GNOME Foundation members and the GNOME
145 Q: Should GNOME programmers switch over to Mono now?
147 A: It is still far to early for discussions of "switching over." No
148 pieces of Mono will be ready within the next six months, and a
149 complete implementation is roughly one year away.
151 We encourage GNOME developers to continue using the existing tools,
152 libraries and components. Improvements made to GNOME will have an
153 impact on Mono, as they would be the "backend" for various classes.
155 Q: Will Mono include compatibility with Bonobo components? What is the
156 relationship between Mono and Bonobo?
158 A: Yes, we will provide a set of classes for implementing and using
159 Bonobo components from within Mono. Mono should allow you to write
160 Bonobo components more easily, just like .NET on Windows allows you
161 to export .NET components to COM.
163 ** Mono and Microsoft: .NET, Hailstorm, and Passport
165 Q: If applications use Mono, does that mean that I have to pay a service fee?
167 A: No. Mono is not related to Microsoft's initiative of
168 software-as-a-service. It is going to provide an open source,
169 Linux-based version of the Microsoft.NET development platform. Its
170 objective is to enable Linux developers to build and deploy cross
171 platform .NET Applications.
173 Q: Is the Mono Project is related to the Microsoft Hailstorm effort? Is
174 Ximian endorsing Hailstorm?
176 A: No. The Mono Project is focused on providing a compatible set of
177 tools for the Microsoft.NET development platform. It does not
178 address, require, or otherwise endorse the MS Passport-based
179 Hailstorm single sign-on system that is part of Windows XP and
182 Q: If you implement .NET, will I depend on Microsoft Passport to run my software?
184 A: No. MS Passport is unrelated to running .NET compatible applications
185 produced with the Mono tools. The only thing you will need is a
186 just-in-time compiler (JIT).
188 Q: Is .NET just a bunch of marketing slogans?
190 A: Although the `.NET initiative' is still quite nebulous, The .NET Framework
191 has been available for some time. Mono is not an implementation of the .NET
192 initiative, just the development framework.
194 Q: What is a 100% .NET application?
196 A: A `100% .NET application' is one that only uses the APIs defined
197 under the System namespace and does not use PInvoke. These
198 applications would in theory run unmodified on Windows, Linux,
199 HP-UX, Solaris, MacOS X and others.
201 Q: If Microsoft will release a port of their .NET platform under the
202 `Shared Source' license, why should I bother with anything else?
204 A: The Shared Source implementation will be expensive and its uses
205 will be tightly restricted, especially for commercial use. We are
206 working towards an implementation that will grant a number of
207 important rights to recipients: use for any purpose,
208 redistribution, modification, and redistribution of modifications.
210 This is what we call <a
211 href="http://www.gnu.org/philosophy/free-sw.html">Free Software</a>
213 Q: Is Mono a free implementation of Passport?
215 A: No. Passport is part of Microsoft's Hailstorm initiative. Mono
216 is just a runtime, a compiler and a set of class libraries.
218 Q: Will the System.Web.Security.PassportIdentity class mean
219 that my software will depend on Passport?
221 A: No. Applications may use that API to contact a Passport site, but
222 are not required to do so.
224 As long as your application does not use Passport, you will not
227 It might even be possible to implement that class with
228 a set of dummy functions, or use an alternate Passport implementation.
230 We do not know at this time whether the Passport protocol is
231 documented and whether we will be able to talk to
234 Q: Will Mono running on Linux make Passport available for Linux?
236 A: No. However, the Passport toolkit for Linux-based web servers is available from
240 ** Mono and Portable.NET
242 Q: What are the differences between Mono and Portable.NET?
244 A: Most of Mono is being written using C#, the only pieces written in
245 C are those who have to absolutely be built using C (The JIT
246 engine, the runtime, the interfaces to the garbage collection
249 The C# compiler and the tools will become reusable C# components.
251 Portable.NET is building its components out of C pieces.
255 Q: Will Mono allow me to run Microsoft Office on Linux?
257 A: No, it will not. Microsoft Office is a Windows application. To
258 learn more about running Windows applications on Intel Unix systems
259 refer to <a href="http://www.winehq.com">the Wine Project</a>.
263 Q: Is Mono just a new way of writing Web Services?
267 Q: If Mono implements the SDK classes, will I be able to write and
268 execute .NET Web Services with it?
270 A: Yes. When the project is finished, you will be able to use the
271 same technologies that are available through the .NET Framework SDK
272 on Windows to write Web Services.
274 Q: What about Soup? Can I use Soup without Mono?
276 A: Soup is a library for GNOME applications to create SOAP servers and
277 SOAP clients, and can be used without Mono. You can browse the
278 source code for soup using <a
279 href="http://cvs.gnome.org/bonsai">GNOME's Bonsai</a>.
283 A: Yes. The CLI contains enough information about a class that
284 exposing it to other RPC systems (like CORBA) is really simple, and
285 does not even require support from an object.
287 We will be implementing CORBA interoperation as an extension to the
288 Mono classes so that we can integrate with Bonobo, just like
289 Microsoft provides COM interoperation classes and support
292 Q: Can I serialize my objects to other things other than XML?
294 A: Yes, although the serializing tools have not yet been planned, and
295 you would probably have to implement them yourself.
297 ** Development Tools and Issues
299 Q: Will it be possible to use the CLI features without using bytecodes
302 A: Yes. The CLI engine will be made available as a shared library.
303 The garbage collection engine, the threading abstraction, the
304 object system, the dynamic type code system and the JIT will be
305 available for C developers to integreate with their applications if
308 Q: Will you have new development tools?
310 A: With any luck, Free Software enthusiasts will contribute tools to
311 improve the developer environment. These tools could be developed
312 initially using the Microsoft implementation of the CLI and then
313 executed later with Mono.
315 Q: What kind of rules make the Common Intermediate Language useful for
318 A: The main rule is that the stack in the CLI is not a general purpose
319 stack. You are not allowed to use it for other purposes than
320 computing values and passing arguments to functions or return
323 At any given call or return instruction, the types on the stack
324 have to be the same independently of the flow of execution of your
327 Q: Is it true that the CIL is ideal for JITing and not efficient for
330 A: The CIL is better suited to be JITed than JVM byte codes, but you
331 can interpret them as trivially as you can interpret JVM byte
337 Q: Why don't you use Java? After all, there are many languages that
340 A: You can get very good tools for doing Java development on free
341 systems right now. <a href="http://www.redhat.com">Red Hat</a> has
342 contributed a <a href="http://gcc.gnu.org">GCC</a> <a
343 href="http://gcc.gnu.org/java">frontend for Java</a> that can take
344 Java sources or Java byte codes and generate native executables; <a
345 href="http://www.transvirtual.com">Transvirtual</a> has implemented
346 <a href="http://www.kaffe.org">Kaffe</a> a JIT engine for Java;
347 Intel also has a Java VM called <a
348 href="http://www.intel.com/research/mrl/orp">ORP</a>.
350 The JVM is not designed to be a general purpose virtual machine.
351 The Common Intermediate Language (CIL), on the other hand, is
352 designed to be a target for a
353 wide variety of programming languages, and has a set of rules
354 designed to be optimal for JITers.
356 Q: Could Java target the CLI?
358 A: Yes, Java could target the CLI. We have details on a <a
359 href="ideas.html#guavac">project</a> that someone could take on to
364 Q: Would you allow other classes other than those in the
367 A: Yes. The Microsoft class collection is very big, but it is by no
368 means complete. It would be nice to have a port of `Camel' (the
369 Mail API used by Evolution inspired by Java Mail) for Mono
372 You might also want to look into implementing CORBA for Mono. Not
373 only because it would be useful, but because it sounds like a fun
374 thing to do, given the fact that the CLI is such a type rich
377 For more information on extending Mono, see our <a
378 href="ideas.html">ideas</a> page.
380 ** Mono and portability
382 Q: Will Mono only work on Linux?
384 A: Currently, we are doing our work on Linux-based systems and
385 Windows. We do not expect many Linux-isms in the code, so it
386 should be easy to port Mono to other UNIX variants.
388 Q: What about Mono on non X-based systems?
390 A: Our main intention at Ximian is to be able to develop GNOME
391 applications with Mono, but if you are interested in providing a
392 port of the Winform classes to other platforms (frame buffer or
393 MacOS X for example), we would gladly integrate them, as long
394 they are under a Free Software License.
396 Q: Will Mono run on Windows?
398 A: We hope so. Currently some parts of Mono only run on Windows
399 (the C# compiler is a .NET executable) and other parts have only
400 been compiled on Linux, but work on Windows with Cygwin.
402 Q: Will Mono depend on GNOME?
404 A: It will depend only if you are using a particular assembly (for
405 example, for doing GUI applications). If you are just interested
406 in Mono for implementing a `Hello World Enterprise P2P Web
407 Service', you will not need any GNOME components.
409 ** Reusing existing Code
411 Q: What projects will you reuse or build upon?
413 A: We want to get Mono in the hands of programmers soon. We are
414 interested in reusing existing open source software.
416 Q: What about Intel's research JIT framework, ORP?
418 A: At this time, we are investigating whether we can use elements of
419 ORP for Mono. ORP is a research JIT engine that has a clear
420 defined API that splits the JIT from the GC system and the actual
421 byte code implementation. It is a research product.
423 Q: What about using GNU Lightning?
425 A: We are also researching <a
426 href="http://www.gnu.org/software/lightning/lightning.html">GNU
429 ** Ximian and Microsoft
431 Q: Is Microsoft helping Ximian with this project?
433 A: Not exactly. Ximian CTO Miguel de Icaza had a friendly
434 conversation with Microsoft software architect David Stutz, but
435 that's about the extent of the contact.
436 Microsoft is interested in other implementations of .NET and are
437 willing to help make the ECMA spec more accurate for this purpose.
439 Ximian representatives have also spoken with Sam Ruby at the ECMA
440 TG3 committee to discuss the same issues.
442 Q: Is Microsoft paying Ximian to do this?
446 Q: Do you fear that Microsoft will change the spec and render Mono
449 A: No. Microsoft proved with the CLI and the C# language that it was
450 possible to create a powerful foundation for many languages to
451 interoperate. We will always have that.
453 Even if changes happened in the platform which were undocumented,
454 the existing platform would a value on its own.
456 The benefits that you can get from the CLI are going to be
457 there with or without `embracing and extending'. We might not be
458 able to run every .NET Windows application on Mono, but then again,
459 it was already easy for someone to just use PInvoke to tie their
460 application to Windows.
462 Q: Are Microsoft and Corel involved in the Mono implementation?
466 Q: Are you writing Mono from the ECMA specs?
468 A: Yes, we are writing them from the ECMA specs and the published
469 materials in print about .NET.
473 Q: What is the difference between CLR (Common Language Runtime) and
474 CLI (Common Language Infrastructure)?
476 A: CLI is the specification of an execution system. The Microsoft
477 implementation of this specification is named CLR.
479 Unless we come up with our own acronym, we could just call ours
480 also CLR, just because it would do exactly the same thing the
481 Microsoft implementation does.
486 Q: Are you working on a GCC front-end to C#?
488 A: We are seeking volunteers for this task. Visit the <a
489 href="contributing.html">contributing</a> section if
490 you'd like to work on this task.
492 Q: How about a GCC backend that will generate CIL images?
494 A: That would be great: it could provide a ton of free compilers that
495 would generate CIL code. This is something that people would want
496 to look into anyway for Windows interoperation in the future.
498 Visit the <a href="contributing.html">contributing</a> section if
499 you'd like to work on this task.
501 Q: What about making a front-end to GCC that takes CIL images and
502 generates native code?
504 A: I would love to see this, specially since GCC supports this same
505 feature for Java Byte Codes. You could use the metadata library
506 from Mono to read the byte codes (ie, this would be your
507 "front-end") and generate the trees that get passed to the
510 Ideally our implementation of the CLI will be available as a shared
511 library that could be linked with your application as its runtime
514 Visit the <a href="contributing.html">contributing</a> section if
515 you'd like to work on this task.
517 Q: But would this work around the GPL in the GCC compiler and allow
518 people to work on non-free front-ends?
520 A: People can already do this by targeting the JVM byte codes (there
521 are about 130 compilers for various languages that target the JVM).
523 Q: Why are you writing a JIT engine instead of a front-end to GCC?
525 A: The JIT engine and runtime engine will be able to execute CIL
526 executables generated on Windows.
530 Q: How fast will Mono be?
532 A: We can not predict the future, but a conservative estimate is that
533 it would be at least `as fast as other JIT engines'.
535 We would like to ship various JIT engines with Mono, just like
536 Microsoft has done with their .NET development platform. We could
537 provide a faster, JIT for fast load times but lower performance,
538 and an and an optimizing JIT that would be slower at generating
539 code but produce more optimal output.
541 The CIL has some advantages over the Java byte code: it is really
542 an intermediate representation and there are a number of
543 restrictions on how you can emit CIL code that simplify creating
546 For example, on the CIL the stack is not really an abstraction
547 available for the code generator to use at will: it is just a way
548 of creating a postfix representation of the parsed tree. At any
549 given call point or return point, the contents of the stack are
550 expected to contain the same object types independently of how the
551 instructions was reached.
556 Q: Will I be able to write proprietary applications that run with
559 A: Yes. The licensing scheme is planned to allow proprietary
560 developers to write applications with Mono.
562 Q: What license or licenses are you using for the Mono Project?
564 A: The C# Compiler is released under the terms of the GPL. The class
565 libraries will be under the LGPL or the GPL with a special
566 exception. The runtime libraries are under the LGPL.
568 Since the LGPL is not suitable for embedded systems development, we
569 are also licensing the libraries under the GPL with the following exception:
571 If you link this library against your own program, then you do not
572 need to release the source code for that program. However, any
573 changes that you make to the library itself, or to any native
574 methods upon which the library relies, must be re-distributed in
575 accordance with the terms of the GPL.
577 This is similar in spirit to <a
578 href="http://www.gnu.org/software/classpath/classpath.html">GNU
581 Q: Can I subclass objects within the LGPL licensed Mono code and still release
582 the resulting software under a closed license?
584 A: Yes. Object Oriented Programming in the class library is a well
585 understood interface barrier, and subclassing does not "count" as a
586 modification, so you may develop proprietary applications with the
589 Q: I would like to contribute code to Mono under a particular
590 license. What licenses will you accept?
592 A: We will have to evaluate the licenses for compatibility first,
593 but as a general rule, we will accept all GPL and LGPL-compatible
594 licenses. If you want to use the BSD
595 license, make sure you use the BSD license without the
596 advertisement clause (The `Ousterhout License').
598 ** Assorted questions
600 Q: You say that the CLI allows multiple languages to execute on the
601 same environment. Isn't this the purpose of CORBA?
603 A: The key difference between CORBA (and COM) and the CLI is that the
604 CLI allows "data-level interoperability" because every
605 language/component uses the same data layout and memory management.
607 This means you can operate directly upon the datatypes that someone
608 else provides, without having to go via their interfaces. It also
609 means you don't have to "marshall" (convert) parameters (data
610 layouts are the same, so you can just pass components directly) and
611 you don't have to worry about memory managment, because all
612 languages/components share the same garbage collector and address
613 space. This means much less copying and no need for reference