GNU MIX Development Kit (MDK)

What is MIX/MIXAL?

MIX is Donald Knuth's mythical computer as described in his monumental work The Art Of Computer Programming. As any of its real counterparts, the MIX features registers, memory cells, an overflow toggle, comparison flags, input-output devices, and a set of binary instructions executable by its virtual CPU. You can program the MIX using an assembly language called MIXAL, the MIX Assembly Language.

So, what's the use of learning MIXAL? The MIX computer is a simplified version of real CISC computers, and its assembly language closely resembles real ones. You can learn MIX/MIXAL as an introduction to computer architecture and assembly programming: see the MDK documentation for a tutorial on MIX and MIXAL.

What is GNU MDK?

MDK (MIX Development Kit) offers an emulation of MIX and MIXAL. The current version of MDK includes the following applications:

• mixasm A MIXAL compiler, which translates your source files into binary ones, executable by the MIX virtual machine.
• mixvm A MIX virtual machine which is able to run and debug compiled MIXAL programs, using a command line interface with readline's line editting capabilities.
• gmixvm A MIX virtual machine with a GTK+ GUI which allows you running and debugging your MIXAL programs through a nice graphical interface.
• mixguile A Guile interpreter with an embedded MIX virtual machine, manipulable through a library of Scheme functions.
• mixal-mode.el An Emacs major mode for MIXAL source files editing, providing syntax highlighting, documentation lookup and invocation of mixvm within Emacs (since version 22, mixal-mode is part of the standard Emacs distribuition).
• mixvm.el An elisp program which allows you to run mixvm within an Emacs GUD window, simultaneously viewing your MIXAL source file in another buffer.

Using the MDK tools, you'll be able to

• write, compile and execute MIXAL programs,
• set breakpoints and run your programs step by step,
• set conditional breakpoints (register change, memory change, etc.),
• collect execution timing statistics,
• trace executed instructions,
• inspect and modify the MIX registers, flags and memory contents at any step,
• simulate MIX input-output devices using the standard output and your file system.

In addition, the MIX virtual machine simulators include an embedded Guile interpreter and, therefore, their functionality can be extended using Scheme.

See the GNU MDK user's manual for a complete description of the toolkit. The MDK suite will run on any GNU or FreeBSD box (see suported platforms) and, of course, is free software.

Downloading stable releases

The GNU MDK source tarball can be found at GNU's FTP site (or any of its mirrors).

MDK is part of the Debian GNU/Linux distribution and can be installed using apt-get. Fink packages (for the CLI and GUI) and a MacPort are also available.

The user's manual is distributed with the source tarball in texinfo format, which is converted to info files during the installation process. It is also available in a variety of formats in the documentation section.

The development source tree

As of March 2008, the source tree of MDK is maintained in a git repository at Savannah with the following coordinates:

• Repository: git://git.sv.gnu.org/mdk.git
• Development branch: master
• Online access here

You can get the sources using the following incantation:

    git clone git://git.sv.gnu.org/mdk.git

or, for those of you behind a firewall,

    git clone http://git.sv.gnu.org/r/mdk.git

For more information on using git, see this tutorial or this Savannah help page.

Further links

• If you like GNU MDK, please consider becoming a FSF Member or making a donation.
• Savannah GNU MDK project page.
• Mailing lists.
• Bug tracking.
• A brief blog post on GNU MDK's 20th aniversary.