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An operating system written in Common Lisp
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froggey Merge pull request #117 from ebrasca/master
 FAT32: Fix small errata and use linux max partition size
Latest commit cf0a835 Mar 7, 2019
Type Name Latest commit message Commit time
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applications The Nyancat telnet server has been shut down Nov 11, 2018
compiler Fix bug in conversion of unreachable blocks Mar 7, 2019
doc Update Oct 31, 2018
drivers fix current-boot-id undefined Oct 3, 2018
file-server Translate drive letters in the file-server on Windows hosts. Dec 18, 2018
file FAT32: Use linux max partition size Mar 7, 2019
gui Colour matrix multiplication. Dec 21, 2018
net Revert "Fix ARP expiration error droping packets" Nov 12, 2018
notes Change the network light colour, it was nearly invisible before. Mar 4, 2016
runtime Improve type checking in some of the SIMD functions Dec 22, 2018
supervisor Fix calculation of virtio ring sizes. Mar 2, 2019
system SUBTYPEP should return a VALID-P value of NIL if the types are unknown. Mar 2, 2019
tools Double floats should always be allocated in the general area. Oct 10, 2018
.gitignore Improve how the cold generator manages build artifacts. Feb 21, 2018
BUILD Point BUILD at the new build system. Apr 26, 2016
LICENCE Update copyright year. Feb 27, 2016 Minor improvement to instructions Aug 25, 2018
config.lisp Added split-sequence library, msg command for the IRC client. Oct 14, 2017
ipl.lisp Rename ext to ext4. Feb 7, 2019
line-edit-mixin.lisp Remove spurious &ALLOW-OTHER-KEYS from INITIALIZE-INSTANCE methods. Sep 24, 2018
lispos.asd Construct the class hierarchy in the cold generator. Sep 27, 2018
lldb.lisp Fix scanning of threads Sep 18, 2018

Mezzano, an operating system written in Common Lisp.


Pre-built images

Demo releases are available through GitHub.

These releases are designed to be run in VirtualBox, though QEMU is also supported. 2GB of RAM, a virtio-net NIC and an Intel HDA audio controller are recommended.

Building from source

See the MBuild repo: (

For help & support, join #mezzano on Freenode (

Major changes since Demo 3

  • FAT32 support has been implemented by Bruno Cichon (ebrasca).
  • McCLIM has been ported by fittestbits.
  • Quicklisp has been ported by Peter S. Housel.
  • Improved introspection tools: DISASSEMBLE and ED have been implemented.
  • Generational collection has been added to the garbage collector.
  • New SSA-based compiler backend, supporting unboxed value representations.
  • Gray streams support has been overhauled.

Major changes since Demo 2

  • Trentino, a media player, has been implemented by Eugene Zaikonnikov.
  • Further improvements to conformance, stability and performance.
  • The CLOS implementation follows the MOP much more closely.
  • More traditional window management.
  • Booting from CD/USB on real hardware is now possible.
  • Driver support for Intel HDA audio devices.
  • VirtualBox guest (mouse & display) integration.

Major changes since Demo 1

  • Many improvements to conformance, stability and performance.
  • The editor has been greatly improved, thanks to Burton Samograd.
  • The system now functions correctly on computers with more than 1GB of RAM.
  • The allocator and garbage collector now make much better use of available memory, with far fewer GC cycles occuring.
  • (ROOM T) prints more detailed information about allocated objects.
  • Transparency and premultiplied alpha support in the GUI.
  • And more!

Additional information

"Hypothymis azurea - Kaeng Krachan" by JJ Harrison ( [CC BY-SA 3.0 (], via Wikimedia Commons

"Mandarin Pair" by © Francis C. Franklin / CC-BY-SA-3.0. Licensed under CC BY-SA 3.0 via Wikimedia Commons -

"Handsome" by Andy Morffew - [CC BY 2.0 (]

Includes Dejavu Fonts 2.37 (

Some icons from Icojam (

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