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Limbo (programming language)

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Limbo
ParadigmConcurrent
Designed bySean Dorward, Phil Winterbottom, Rob Pike
DeveloperHistoric: Bell Labs, Vita Nuova Holdings
Current: Terzarima Systems, Inferno64 Project
First appeared1995; 31 years ago (1995)
Typing disciplineStrong
OSInferno
LicenseGNU GPL v2, see NOTICE in limbo subfolder of the tarball
Websiteweb.archive.org/web/20250207231314/http://www.vitanuova.com/inferno/limbo.html
Major implementations
Dis virtual machine
Influenced by
C, Pascal, CSP, Alef, Newsqueak
Influenced
Stackless Python, Go, Rust

Limbo is a programming language for writing distributed systems and is the language used to write applications for the Inferno operating system. It was designed at Bell Labs by Sean Dorward, Phil Winterbottom, and Rob Pike.[1]

The Limbo compiler generates architecture-independent object code which is then interpreted by the Dis virtual machine or compiled just before runtime to improve performance. Therefore all Limbo applications are completely portable across all Inferno platforms.[2][3]

Limbo's approach to concurrency was inspired by Hoare's communicating sequential processes (CSP), as implemented and amended in Pike's earlier Newsqueak language and Winterbottom's Alef.[1]

Language features

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Limbo[2] supports the following features:

Virtual machine

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The Dis virtual machine that executes Limbo code is a CISC-like VM, with instructions for arithmetic, control flow, data motion, process creation, synchronizing and communicating between processes, loading modules of code, and support for higher-level data-types: strings, arrays, lists, and communication channels.[4] It uses a hybrid of reference counting and a real-time garbage-collector for cyclic data.[5]

Aspects of the design of Dis were inspired by the AT&T Hobbit microprocessor, as used in the prototype BeBox.[3] A possible production of the formal logical specification for the Dis Virtual machine[6] has been discussed by Charles Forsyth of Terzarima Systems.[7] This is possible due to the regular structure and size of the virtual Machine compared to similar virtual machines.[6]

Further developments of the Dis virtual machine

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The Inferno64[8] project has extended the Dis virtual machine to 64-bits for application development on 64-bit architectures and platforms. [9] The RiceVM project was started in 2026[10] that has made a implementation of the Dis virtual machine and Limbo interpreter in Rust which supports Windows 11, macOS, and Linux. [11]

Examples

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Limbo uses Ada-style definitions as in:

name := type value;
name0,name1 : type = value;
name2,name3 : type;
name2 = value;

Hello world

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implement Command;

include "sys.m";
    sys: Sys;

include "draw.m";

include "sh.m";

init(nil: ref Draw->Context, nil: list of string)
{
    sys = load Sys Sys->PATH;
    sys->print("Hello World!\n");
}

Books

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The 3rd edition of the Inferno operating system and Limbo programming language are described in the textbook Inferno Programming with Limbo[12] ISBN 0-470-84352-7 (Chichester: John Wiley & Sons, 2003), by Phillip Stanley-Marbell.

Another textbook The Inferno Programming Book: An Introduction to Programming for the Inferno Distributed System[13] was started by Martin Atkins, Rob Pike, Howard Trickey and Charles Forsyth[14] but never released.

See also

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References

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  1. 1 2 Kernighan, Brian W. (1997-07-12). "A Descent into Limbo". www.gbppr.net. Lucent Technologies. Archived from the original on 2026-03-05. Retrieved 2026-08-10.
  2. 1 2 Ritchie, Dennis M. "The Limbo Programming Language". doc.cat-v.org. Vita Nuova. Retrieved 2026-08-10.
  3. 1 2 Winterbottom, Phil; Pike, Rob (1997-02-27). "The design of the Inferno virtual machine". 9p.io. Proceedings, IEEE COMPCON 97: San Jose, California, February 23-26, 1997. ISBN 978-0818678042. Retrieved 2026-08-10.{{cite web}}: CS1 maint: periodical has ISBN (link) CS1 maint: url-status (link)
  4. ↑ "Dis Virtual Machine Specification". Lucent Technologies, Vita Nuova. 2003. Retrieved 10 August 2026.{{cite web}}: CS1 maint: url-status (link)
  5. ↑ Lorenz Huelsbergen and Phil Winterbottom (1998). "Very Concurrent Mark and Sweep Garbage Collection without Fine-Grain Synchronization" (PDF). 1998 International Symposium on Memory Management.
  6. 1 2 "Formal Specification for Dis VM?". groups.google.com. Retrieved 2026-08-10.
  7. ↑ "Charles Forsyth (Terzarima Systems)". terzarima.net. Archived from the original on 2026-05-20. Retrieved 2026-08-10.
  8. ↑ "Inferno64 - Distributed Compute Grid". inferno64.org. Retrieved 2026-08-10.
  9. ↑ caerwynj. "inferno64/limbo at main · caerwynj/inferno64". GitHub. Retrieved 2026-08-10.
  10. ↑ "A Dis virtual machine and Limbo compiler in Rust". www.reddit.com. Retrieved 2026-08-15.
  11. ↑ "RiceVM Documentation". Github. Retrieved 2026-08-15.
  12. ↑ Stanley-Marbell, Charles (2003). Inferno programming with Limbo (1st ed.). Wiley. pp. xxix. ISBN 978-0470843529.
  13. ↑ Atkins, Martin; Pike, Rob; Trickey, Howard (2005-06-01). The Inferno Programming Book: An Introduction to Programming for the Inferno Distributed System. Hoboken, NJ, USA: John Wiley & Sons, Inc. ISBN 978-0-470-84971-2.
  14. ↑ "The Inferno Programming Book: An Introduction to Programming for the Inferno Distributed System - Atkins, Martin; Forsyth, Charles; Pike, Rob; Trickey, Howard: 9780470849712 - AbeBooks". www.abebooks.co.uk. Retrieved 2026-08-10.
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