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GNUstep Frequently Asked Questions with Answers
***********************************************
Last updated 26 February 2001 Please send corrections to
<gnustep-maintainer@gnu.org>.
GNUstep General Information
===========================
What is GNUstep?
----------------
GNUstep is the Free Software Foundation's effort to implement NeXT
Software Inc.'s (now Apple Inc.) OpenStep Standard. The project is not
finished, however some components are useable now.
The GNUstep project consists of the following sub-projects:
* GNU Objective C Compiler and Objective C Runtime Library -
Although not actually a component of GNUstep, GCC and the GNU
Objective C Runtime Library are integral to GNUstep, since they
are used to make every GNU Objective C program.
* GNUstep Base Library - Code for non-graphical objects, such as
strings, collections, archiving support and distributed objects
messaging. (Including functionality similar to OpenStep's
`FoundationKit'.)
* GNUstep GUI Library - Code for graphical objects used in making a
Graphical User Interface (GUI). This includes buttons, sliders,
text fields, windows, menus, etc. (Including functionality
similar to OpenStep's `AppKit'.)
* GNUstep DisplayGhostscript Server - A server that draws PostScript
graphics to the screen, and receives events from the keyboard and
mouse. It is based on GhostScript. There is also an DPS extension
to Xfree*6 that is usable.
* Various Tools and applications, including GORM, The GNUstep
interface builder for graphically assembling application
interfaces, and ProjectCenter, a project manager.
What is the OpenStep standard?
------------------------------
OpenStep is an Application Programming Interface (API) for creating
applications using the Objective C language. It was published by NeXT
Computer Inc. in 1994.
OpenStep consists of three parts: the `FoundationKit', a library of
non-graphical objects; the `AppKit', a library of objects usful in
creating graphical applications; and `Display Postscript', an interface
for drawing to the screen using the PostScript graphics language.
You can obtain a copy of the OpenStep standard from the GNUstep web
site <http://www.gnustep.org> or it's mirror sites.
What platforms does GNUstep run on?
-----------------------------------
Well tested current builds:
Ix86/GNU-Linux
PPC/GNU-Linux
Recent builds -
Ix86 Unixware-2.? Ix86 FreeBSD-3.0 (ELF) Ix86 OpenBSD-2.4 (static
libraries) Sparc SUNOS-4.1.3 PowerPC GNU/Linux
Probably a few days porting to any other Unix system where current
gcc/egcs compilers and gdb debugger work. See the GNUstep-HOWTO file or
<http://www.gnustep.org/information/machines_toc.html> for more
machines.
Does GNUstep run on Windows?
----------------------------
The primary targets for GNUstep are free 'Unix' platforms such as
GNU/Linux.
That being said, the base library should run on Windows-NT,98 with
the Cygwin unix emulation library from Cygnus
(http://sourceware.cygnus.com/cygwin/) or the MinGW libraries. At
present there are a few problems with networking (Distributed Objects)
support, but the library is believed to work.
The gui library needs a win32 backend library to work under
Windows-NT. The backend library is a thin layer that converts the
GNUstep methods to handle drawing of GUI elements to calls to the win32
api. This is a project looking for a volunteer.
The application-wrapper used for GNUstep already allows for multiple
binaries to be stored for different systems, so you should be able to
write once, deploy anywhere.
What is GNUstep's position towards KDE and the GNOME project?
-------------------------------------------------------------
You can use GNUstep with GNOME and/or KDE. GNUstep displays on top
of X11. You can still do programming in C (since Objective-C is just a
superset of C), and when (if?) GCC gets around to it, you'll be able to
mix C++ and Objective-C code in the SAME file.
GNUstep, is much more than a window manager or desktop environment.
It frees you to develop cross-platform applications without the work of
developing an OS independent framework from scratch. It gives you lots
of basic functionality, from Font Panels to Unicode strings to
Distributed Objects.
Is the Objective C API for GTK related?
---------------------------------------
No. GNUstep applications provide their GUI via the OpenStep API,
which provides fully object-oriented access to GUI manipulation.
The object-oriented nature of the libraries and language make it
much easier for new users to create their own subclasses rather than
simply using the supplied widgets as in other frameworks.
How about implementing parts of the Application Kit with GTK?
-------------------------------------------------------------
Yes and No - The GNUstep architecture provides a single,
platform-independent, API for handling all aspects of GUI interaction
(implemented in the gstep-gui library), with a backend architecture
that permits you to have different display models (display postscript,
X-windows, win32, berlin ...) while letting you use the same code for
printing as for displaying. Use of GTK in the frontend gui library
would remove some of those advantages without adding any.
That being said, a backend library could be implemented using gtk if
anyone wanted to do so. Since the frontend library handles most of the
work involved in implementing the OpenStep API, the backend is a
relatively thin layer and the advantages of GTK over direct xlib or
win32 calls is likely to be minimal. If/when GTK is ported to more
systems, a backend written using it could be a valuable asset -
volunteers are, as always, wecome.
Which compiler can I use? Where can I get it?
---------------------------------------------
Use gcc-2.8.1 or later, from any GNU ftp site or, on some platforms
you must use egcs-1.1.1 or later, from http://egcs.cygnus.com/
Which Foundation Library can I use?
-----------------------------------
That depends ...
If you only want to use the database package - gnustep-db, you can
use either the gnustep base library or libFoundation.
If you want to develop/use GNUstep gui applications, you must use
the gnustep-base library since libFoundation is (13-Feb-2000) missing
much essential functionality.
How do you use the gnustep-make package?
----------------------------------------
Good question. Read the tutorials at the GNUstep web site. Also,
use the makefiles in the libraries, tool directories, and test
applications as examples.
How can I get GNUstep?
----------------------
Get the HOWTO from
<http://www.gnustep.org/resources/documentation/GNUstep-HOWTO> Get the
latest release from <ftp://ftp.gnustep.org>. If you're really
adventurous, get the latest snapshot by anonymous ftp from
<ftp://ftp.gnustep.org:/pub/daily-snapshots>
Use anonymous CVS to keep up to date - instructions are in the HOWTO.
How do you run GNUstep?
-----------------------
You are presumably under the misapprehension that GNUstep is some
sort of window manager.
It isn't.
GNUstep is a whole load of things - primarily a set of libraries for
developing software.
At present, it's those libraries, plus various command-line based
support tools and service providing daemons. In the future, it will be
the libraries, plus the support tools, plus various GUI development
tools, a GUI desktop/workspace application etc.
At no stage will you ever 'run' GNUstep - you will run applications
and tools and will make use of it's services (though at some point you
may well find packages distributed as 'GNUstep' systems in the way that
you get 'Linux' systems packaged today).
Current tools are -
The makefiles package
To make building GNUstep tools and apps simple.
The 'openapp' script
To start up a GUI application from the command line.
The defaults tools
To read, create, delete, and modify user defaults from the command
line.
The name server
To permit applications and tools to locate each other and
communicate.
The pasteboard server
To permit cut-and-paste, drag-and-drop, and to let applicationsm
and tools transparently provide services to each other.
The distributed notification center
To permit applications and tools to be notified of arbitrary
external events.
The 'make_services' program
To locate (and cache information about) applications that are
willing to provide services to other applications.
The 'set_show_service' program
A command-line utility to determine what services an application
should be permitted to offer on it's 'services' menu.
If you want to see a sample GUI application running - you need to
build GNUstep for use with the 'xgps' library (configuring it with with
the option -with-library-combo=gnu-gnu-gnu-xgps) and look at the
example applications in the gstep-examples package. Build 'Finger' or
'Ink' and start it with 'openapp Finger.app' or 'openapp Ink.app'
To look best - use WindowMaker (the currently preferred GNUstep
window manager) as your window manager.
Is there a web site?
--------------------
See http://www.gnustep.org/ - the main web site.
When is GNUstep intended to be available?
-----------------------------------------
It's usable now (for an experienced developer). Releases are made
about every six months. However, if you are a serious developer, it's
probably best to use the latest snapshots. See the GNUstep web site
for a release schedule.
What is usable?
---------------
gstep-make does pretty much what the makefiles in NeXTstep do.
gstep-base (Foundation) stuff should work fine for almost all projects.
gstep-db is only EOF-1.0 compatible but should work ok. gstep-gui
(AppKit) is usable with the xgps backend, and you would probably have
to fix some things in the gui library. Cut-and-paste works, services
work, drag-and-drop works, the NSText classes partially work.
gstep-xgps basic functionality is quite usable. gstep-xdps is mostly
usable. DGS (Display Ghostscript) is usable but slow.
Compiling and Developing
========================
Can I run NeXT OPENSTEP or Apple Rhapsody programs on GNUstep?
--------------------------------------------------------------
You can't run these programs on GNUstep, but if you have the source
code for the programs, you should be able to port them to GNUstep and
compile them. Whether or not you will be able to run them depends on how
complete GNUstep is at the time.
Is it easy to port OPENSTEP and Rhapsody programs to GNUstep?
-------------------------------------------------------------
It is probably easy for simple programs. You'll have to use nfmake
<http://karl.nfox.com> to translate the PB.prject file to GNUstep
Makefiles, or rewrite the Makefiles yourself. You will also have to
translate the NIB files (if there are any) to GNUstep model files using
the nib2gmodel program (from
<ftp://ftp.gnustep.org/pub/gnustep/dev-apps>).
Is there an Interface Builder for GNUstep?
------------------------------------------
There is an Interface Builder for GNUstep called Gorm, but it is in
alpha release, so it may not work perfectly. You can get it from the
GNUstep CVS repository (cvs -z3 checkout Gorm). The Project Manager
ProjectCenter is also new.
Can I use my original NIB files?
--------------------------------
No - NeXT/Apple never documented their nib format, so GNUstep
supports both the 'gmodel' format (which stores information as text
(property-lists) and can therefore be edited 'by hand') and binary
archive format (which can be edited by Gorm). There IS a conversion
tool that can be compiled under OPENSTEP to convert OPENSTEP nib files
to GNUstep gmodel files.
Will code without NIB files work?
---------------------------------
Well, GNUstep implements the OpenStep API, not the old NeXTstep API
but, Yes - once the gui library is complete, OpenStep or MacOS-X code
should work without translation under GNUstep.
Is GNUstep following Apple's Changes to OpenStep?
-------------------------------------------------
Yes - gstep-base already contains the documented changes in the
Foundation library. GNUstep aims to be compatible with both the
OpenStep specification and with MacOS-X It should be easy to write an
application that compiles cleanly under both GNUstep and Yellow Box.
Do we have to have the NeXTstep look and feel?
----------------------------------------------
Gnustep is aiming for something like the NeXTstep-3.3 look and feel
This is mostly determined by the gui backend library. In the case of
the two existing backends (xdps and xgps), both are designed to look
like NeXTstep/OPENSTEP. If someone wants to write a backend with a
different look, they can. This would only be a few man-months work.
Can one use the hybrid "Objective-C++"
--------------------------------------
that one could on the NeXT?
No - at present the GNU compiler (gcc or egcs) does not support
"Objective-C++" There are no specific plans to make it do so, but any
volunteers to do it would be welcome.
Is there a plan to support the Java/YellowBox Bindings?
-------------------------------------------------------
Yes. The GNustep Java library/bridge called JIGS is available now.
JIGS is a free (LGPL) Java Interface for GNUstep; it can automatically
wrap Objective-C libraries based on GNUstep making them accessible
directly to the Java programmer as if they were Java libraries. As a
side effect, it is also possible to use the whole engine in the reverse
way: JIGS provides a high level API to allow Objective-C programmers to
start java virtual machines inside GNUstep Objective-C code and access
java objects in the java virtual machine transparently, as if they were
objective-C objects.
What if I compile GNUstep under OPENSTEP/MacOS X Server?
--------------------------------------------------------
No - GNUstep uses the X-windows display postscript extension - the
interface to that is not the same as the interface to the
OPENSTEP/MacOS-X windows server. While someone could write a backend
library to provide the interface, nobody has bothered to date.
Also - there is no known recent port to OPENSTEP of the base library.
How can I help with GNUstep?
----------------------------
1. Write/debug library code 2. Write documentation 3. Update the
TODO list and library headers 4. Write applications
Some general advice -
Let people know what you are doing. Break your project up into the
smallest units you can. Feed back frequent updates to the maintainers.
Ask questions in the discussion mailing list.
Do remember that any changes beyond a few lines of code (or
documentation) require a disclaimer or copyright assignment to the Free
Software Foundation before they can be incorporated into the project.
Get in touch with the maintainer of the library you are working on
about this.
Don't start with large-scale reorganisation of anything - instead,
get a general idea in mind of what you want to do, and proceed as much
as possible with incremental changes that don't break anything - that
way you can make those incremental changes available to the rest of the
community at frequent intervals.
Don't be afraid to give up - there is no shame in finding out that
you have take on too large/complex a project. It's much better to
'resign' and take on a smaller job than to just stop without telling
anyone.
How do I start writing code?
----------------------------
There is plenty of unimplemented stuff in the gui library and
backend libraries that volunteers can work on - just browse through the
code and see if it conforms to the documentation.
Specific tasks are noted in the developers section on the
www.gnustep.org website.
Once you have coded something, you could always write a testcase and
documentation for it :-)
How do I start writing documentation?
-------------------------------------
Our documentation format is called gsdoc, which is an SGML format
for Objective-C documentation in the same vein as XML. We are also
trying to use Autodoc to self document source code. The gsdoc
translator is included with the base library.
Newcomers could write documentation for individual classes by
comparing the OpenStep specification, the MacOS-X documentation, and
the GNUstep source. Documentation should clearly note where individual
methods are specific to OpenStep, MacOS-X or are GNustep extensions.
More experienced people could write documentation on general
programming topics, and tutorials for new users.
Anyone willing to write documentation, either tutorials for using
GNUstep, or reference documentation for individual classes, should
either write it in gsdoc or as plain ascii text for someone else to
format into gsdoc.
GNUstep documentation should have copyright assigned to the Free
Software Foundation.
How do I update the task list?
------------------------------
The task list (<http://www.gnustep.org/developers/tasks.html>) is
supposed to tell people what jobs are waiting to be done.
One job of major importance that pretty much anyone can do is to
look for jobs to add to the task list. In the case of methods from the
OpenStep specification or the MacOS-X documentation not being present
in the GNustep libraries, it is also helpful to add the method
prototypes to the library header files.
At the moment, send changes to Adam Fedor <fedor@gnu.org> or Richard
Frith-Macdonald <richard@brainstorm.co.uk>
We are hoping to have a system where people can update the list
directly.
A beginner can look through the MacOS-X documentation, the OpenStep
specification and the GNUstep source and contribute TODO items.
If a class or method is in MacOS-X and OpenStep but is not in
GNUstep - it's a high priority TODO and should at least be added to the
GNUstep headers and a dummy version added to the source with a FIXME
comment.
If a class or method is in MacOS-X but not OpenStep or GNUstep -
it's a low priority TODO. It should be added to the GNUstep headers
bracketed in `#ifndef STRICT_OPENSTEP'
If a class or method is in OpenStep but not in MacOS-X or GNUstep -
it's a low priority TODO. It should be added to the GNUstep headers
bracketed in `#ifndef STRICT_MACOS_X'
There are a couple of people working on this already, so it's a good
idea to get in touch with Adam or Richard to coordinate efforts.
How do I start writing tests?
-----------------------------
You can write testcases - where the libraries fail tests, you could
either fix the problem, or add it to the task list.
To write testcases, you need to use anonymous CVS to install the
latest gstep-core snapshot you can find. Then checkout the 'tests'
module from CVS. In the 'tests' directory, you will find a regression
testing framework for gstep-base. In order to use this you will also
need a recent (v 1.3.2 or later) copy of Guile (you can get this from a
GNU ftp site) and will need to hacke checked out, built, and installed
the 'guile' package from the GNUstep CVS repository.
At present, there is no such framework for the gui library - If you
are interested in working on one, contact <richard@brainstorm.co.uk>
How do I start writing applications?
------------------------------------
You can either look at the links on the GNUstep website for
applications that have been started, and email their owners to
volunteer to help, or you can start your own project.
If you are starting your own project, you need to - 1. Get the
latest snapshot of GNUstep and build it to use the 'xgps' or 'xdps'
backend library. 2. Look at the example applications (particularly
Ink.app) in the gstep-examples package directory as a basis for your
work. 3. Be prepared to a) ask for help on the gnustep-discuss
mailing list b) fix bugs and implement missing functionality in the
gui and xgps libraries.
How can I help with the GNUstep website?
----------------------------------------
Talk to Adam Fedor <fedor@gnu.org>, the maintainer.
The GNUstep website is kept as a CVS module, but the largest portions
of it (the FAQ, the TODO list, and the Documentation) are actually
generated from files in the individual GNUstep packages.
If you want to update the FAQ or TODO list or documentation - grab
the latest snapshot of the GNUstep core you can find, update it from
the CVS repository, and work with the contents of the appropriate
documentation directory.
If you want to work on other parts of the website - capture the
pages you want to edit in your web browser (at http://www.gnustep.org).
If you can't do that, you can grab a copy of the website via anonymous
CVS -
$ CVSROOT=:pserver:anoncvs:@cvs.net-community.com:/gnustep-www
$ export CVSROOT
$ cvs login (password anoncvs)
$ checkout -z3 www
The main task with the website is to figure out which bits are
out-of-date (or wrong) and update/mark-as-outdated as required.
Current status -
The 'developers section' of the FAQ is being worked on by
<stevensl@mindspring.net>, and we are looking at rewriting the more
general parts of the FAQ.
How do I compile GNUstep on my machine?
---------------------------------------
Read the file `GNUstep-HOWTO', which comes with the GNUstep
distribution, and also is available separately on the GNUstep ftp
sites. A PDF version also exists on the web site called
`GnustepInstall.pdf'.
Are there any precompiled packages available?
---------------------------------------------
Check <http://www.gnustep.org/resources/sources.html> for links to
sites with RPMS, and perhaps in the future, Debian packages. In some
cases. You can check the debian site for preconfigured GNUstep packages.
I get an error compiling mframe.m in gnustep-base.
--------------------------------------------------
This occurs on some GNU/Linux systems. You'll need to change the
optimization level, usually like this:
make OPTFLAG=-O
GNU Objective C Compiler and Objective C Runtime Library
========================================================
What is the Objective C Runtime Library?
----------------------------------------
The Objective C Runtime Library provides C functions and data
structures required to execute an Objective C program.
The GNU Objective C Runtime Library offers everything NeXT's runtime
does, including Categories, Protocols, `+poseAs:', thread-safety, class
initialization on demand, delayed loading of classes, and
initialization of static instances (such as @""-style string objects).
It also has several improvements over NeXT's implementation:
* NeXT's runtime requires an extra function call (objc_msgSend) for
each message that is sent; (the function looks up the receiving
instance's implementation of the method). GNU's implementation is
faster because it does not use an extra function call. Instead, it
inlines a short piece of code that makes two pointer hops into a
method dispatch table; because the code is inlined, it does not
incur the overhead of a function call.
* When running in thread-safe mode, NeXT's runtime must aquire a
global mutual exclusion lock every time a message is sent; this is
extremely slow. GNU's runtime, amazingly, sends messages just as
fast in thread-safe mode as it does in single-thread mode--the
code path does not contain even a single extra instruction! The
GNU runtime only needs locks when certainly structures are
written, not read; the structures are written relatively
infrequently: only at class initialization and when `+poseAs:' is
called.
* GNU's runtime provides "selector-types" along with each selector;
NeXT's does not. A selector-type is a string that describes the C
variable types for the method's return and argument values. Among
other uses, selector-types is extrememly helpful for fast
distributed objects implementations, (see GNUstep Base Library
Section, below).
* Many of the GNU functions have different names than their
corresponding NeXT functions; the GNU names conform to the GNU
coding standards.
* GNU's runtime library has a new class heirarchy manipulating
method called `-transmuteClassTo:'. It can change the class of an
instance to a cousin class of the same instance-size.
* NeXT's compiler, `cc', is based on an old version of `gcc'. GNU's
compiler is, of course, the latest version of `gcc', and therefore
contains all the latest enhancements.
Does it allow a mixture of Objective C and C++?
-----------------------------------------------
No. Unlike NeXT's `cc', GNU GCC does not support source files
containing both Objective C and C++. People at Cygnus have mentioned
that they would be willing to do the work--if they were paid for it, of
course. Several people are interested in seeing this happen. Send
email to `discuss-gnustep@gnu.org' if you are interesting in pushing
this issue, so that the efforts of all those people interested can be
coordinated.
Also, unlike NeXT's `cc', GNU GCC does not support the `extern
"Objective-C"' construct.
Where can I find more information?
----------------------------------
The FAQ associated with the newsgroup `comp.lang.objective-c'
contains more information about GNU Objective C.
GNUstep Base Library
====================
What is the GNUstep Base Library?
---------------------------------
The GNUstep Base Library is a library of general-purpose,
non-graphical Objective C objects. For example, it includes classes
for strings, object collections, byte streams, typed coders,
invocations, notifications, notification dispatchers, moments in time,
network ports, remote object messaging support (distributed objects),
event loops, and random number generators.
It provides functionality that aims to implement the non-graphical
portion of the OpenStep standard (the Foundation library).
What is its current state of development?
-----------------------------------------
It is about 98 percent of the way to having all the OpenStep classes
(and the later OPENSTEP/Rhaspody classes) fully implemented. Normal
work can already be done using the library since the missing 2 percent
are the least-often-used features or are simply not up to date with the
latest MacOS-X spec. Over 60,000 lines of code have already been
written.
What are the features of GNU Distributed Objects?
-------------------------------------------------
GNU Distributed Objects has many of the features of other distributed
objects implementations, but, since it is free software, it can be
ported to platforms for which other distributed objects implementations
are not available.
[NOTE: The GNU distributed object facilities have the same
ease-of-use as NeXT's; be warned, however, that they are not compatible
with each other. They have different class heirarchies, different
instance variables, different method names, different implementation
strategies and different network message formats. You cannot
communicate with a NeXT NSConnection using a GNU Connection.
Here are some differences between GNU distributed objects and NeXT's
distributed objects: NeXT NSDistantObject asks it's remote target for
the method encoding types and caches the results; GNU NSDistantObject
gets the types directly from the local GNU "typed selector" mechanism
if the information is known locally and only queries the remote target
or caching encoding types when using a method that is not known to the
local process. The NSProxy for the remote root object always has name 0
and, once set, you cannot change the root object of a NSConnection; the
GNU Proxy for the remote root object has a target address value just
like all other Proxy's, and you can change the root object as many
times as you like. ].
GNUstep GUI Library
===================
What is the GUI Library?
------------------------
The GNUstep GUI Library is a library of objects useful for writing
graphical applications. For example, it includes classes for drawing
and manipulating graphics objects on the screen: windows, menus,
buttons, sliders, text fields, and events. There are also many
peripheral classes that offer operating-system-independent interfaces to
images, cursors, colors, fonts, pasteboards, printing. There are also
workspace support classes such as data links, open/save panels,
context-dependent help, spell checking.
It provides functionality that aims to implement the `AppKit'
portion of the OpenStep standard. However the implementation has been
written to take advantage of GNUstep enhancements wherever possible.
Explain the organization of the front- and back-ends
----------------------------------------------------
The GNUstep GUI Library is divided into a front- and back-end. The
front-end contains the majority of implementation, but leaves out the
low-level drawing and event code. A back-end can override whatever
methods necessary in order to implement low-level drawing event
receiving. Different back-ends will make GNUstep available on various
platforms. The default GNU back-end will run on top of X Windows and
the DisplayGhostScript Server. Other back-ends could allow GNUstep to
run on OpenGL, OS/2, and WIN32 graphics/event platforms. Much work
will be saved by this clean separation between front- and back-end,
because it allows different platforms to share the large amount of
front-end code.
What is the current state of development of the front-end?
----------------------------------------------------------
Many of the classes are well implemented, if not thouroughly tested.
See the GNUstep web sites and read status information contained in the
distribution for the most up-to-date information.
What is the current state of development of the X/DPS back-end?
---------------------------------------------------------------
It works, but is slow and buggy. A lot of work could be done.
GNUstep DisplayGhostScript Server
=================================
What is the Display Ghostscript Server?
---------------------------------------
It is a free implementation of a Display PostScript server based on
the ghostscript program by Aladdin software.
What is its current state of development?
-----------------------------------------
GNU contracted with Aladdin software to add some key features to
ghostscript so it could be used as a DPS server. This work has mostly
been done, althought Aladdin did not completely finish the work that
they were contracted for. DGS works fairly well with a single context
and will soon work with multiple contexts. Alpha channel and compositing
currently doesn't work, but should before the end of 2000 (It's already
been fixed in Ghostscript, just not released).
What is the relationship between the Display Ghostscript Server and X Windows?
------------------------------------------------------------------------------
Display Ghostscript runs on top of X Windows.
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