Limbo is a

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

for writing distributed systems and is the language used to write

applications Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a c ...

for the Inferno operating system. It was designed at

Bell Labs Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mult ...

by Sean Dorward, Phil Winterbottom, and

Rob Pike Robert "Rob" Pike (born 1956) is a Canadian programmer and author. He is best known for his work on the Go programming language and at Bell Labs, where he was a member of the Unix team and was involved in the creation of the Plan 9 from Bell Lab ...

. The Limbo

compiler In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs th ...

generates

architecture Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and constructing buildings ...

-independent

object code In computing, object code or object module is the product of a compiler. In a general sense object code is a sequence of statements or instructions in a computer language, usually a machine code language (i.e., binary) or an intermediate langu ...

which is then interpreted by the

Dis virtual machine 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. The Limbo comp ...

or compiled just before runtime to improve performance. Therefore all Limbo applications are completely portable across all Inferno platforms. Limbo's approach to concurrency was inspired by Hoare's

communicating sequential processes In computer science, communicating sequential processes (CSP) is a formal language for describing patterns of interaction in concurrent systems. It is a member of the family of mathematical theories of concurrency known as process algebras, or pr ...

(CSP), as implemented and amended in Pike's earlier

Newsqueak Newsqueak is a concurrent programming language for writing application software with interactive graphical user interfaces. Newsqueak's syntax and semantics are influenced by the C language, but its approach to concurrency was inspired by C. ...

language and Winterbottom's

Alef Aleph (or alef or alif, transliterated ʾ) is the first letter of the Semitic abjads, including Phoenician , Hebrew , Aramaic , Syriac , Arabic ʾ and North Arabian 𐪑. It also appears as South Arabian 𐩱 and Ge'ez . These lette ...

Language features

Limbo supports the following features: *

modular programming Modular programming is a software design technique that emphasizes separating the functionality of a program into independent, interchangeable modules, such that each contains everything necessary to execute only one aspect of the desired functi ...

concurrent programming Concurrent means happening at the same time. Concurrency, concurrent, or concurrence may refer to: Law * Concurrence, in jurisprudence, the need to prove both ''actus reus'' and ''mens rea'' * Concurring opinion (also called a "concurrence"), ...

* strong

type checking In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a type to every "term" (a word, phrase, or other set of symbols). Usually the terms are various constructs of a computer progr ...

at compile and run-time *

interprocess communication In computer science, inter-process communication or interprocess communication (IPC) refers specifically to the mechanisms an operating system provides to allow the processes to manage shared data. Typically, applications can use IPC, categor ...

over typed channels * automatic

garbage collection Waste collection is a part of the process of waste management. It is the transfer of solid waste from the point of use and disposal to the point of treatment or landfill. Waste collection also includes the curbside collection of recyclable m ...

* simple

abstract data type In computer science, an abstract data type (ADT) is a mathematical model for data types. An abstract data type is defined by its behavior (semantics) from the point of view of a '' user'', of the data, specifically in terms of possible values, po ...

Virtual machine

The Dis virtual machine that executes Limbo code is a CISC-like VM, with instructions for arithmetic,

control flow In computer science, control flow (or flow of control) is the order in which individual statements, instructions or function calls of an imperative program are executed or evaluated. The emphasis on explicit control flow distinguishes an ''im ...

, data motion,

process A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management * Business process, activities that produce a specific s ...

creation, synchronizing and communicating between processes, loading modules of code, and support for higher-level data-types: strings, arrays, lists, and communication channels. It uses a hybrid of

reference counting In computer science, reference counting is a programming technique of storing the number of references, pointers, or handles to a resource, such as an object, a block of memory, disk space, and others. In garbage collection algorithms, referen ...

and a

real-time Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...

garbage-collector for cyclic data. Aspects of the design of Dis were inspired by the

AT&T Hobbit The AT&T Hobbit is a microprocessor design that AT&T Corporation developed in the early 1990s. It was based on the company's CRISP (C-language Reduced Instruction Set Processor) design, which in turn grew out of the C Machine design by Bell Labs o ...

microprocessor, as used in the original

BeBox The BeBox is a dual CPU personal computer, briefly sold by Be Inc. to run the company's own operating system, BeOS. It has PowerPC CPUs, its I/O board has a custom "GeekPort", and the front bezel has "Blinkenlights". The BeBox made its debut ...

Examples

Limbo uses Ada-style definitions as in: name := type value; name0,name1 : type = value; name2,name3 : type; name2 = value;

Hello world

implement Command; include "sys.m"; sys: Sys; include "draw.m"; include "sh.m"; init(nil: ref Draw->Context, nil: list of string)

Books

The 3rd edition of the Inferno operating system and Limbo programming language are described in the textbook ''Inferno Programming with Limbo'' (Chichester: John Wiley & Sons, 2003), by Phillip Stanley-Marbell. Another textbook ''The Inferno Programming Book: An Introduction to Programming for the Inferno Distributed System'', by Martin Atkins, Charles Forsyth,

and Howard Trickey, was started, but never released.

References

External links

Vita Nuova page on Limbo

A Descent into Limbo
by

Brian Kernighan Brian Wilson Kernighan (; born 1942) is a Canadian computer scientist. He worked at Bell Labs and contributed to the development of Unix alongside Unix creators Ken Thompson and Dennis Ritchie. Kernighan's name became widely known through co-aut ...

The Limbo Programming Language
by

Dennis M. Ritchie Dennis MacAlistair Ritchie (September 9, 1941 – October 12, 2011) was an American computer scientist. He is most well-known for creating the C programming language and, with long-time colleague Ken Thompson, the Unix operating system and B ...

an
Addendum
by Vita Nuova.
Inferno Programming with Limbo
by Phillip Stanley-Marbell
Threaded programming in the Bell Labs CSP style
* * . * . * . {{DEFAULTSORT:Limbo (Programming Language) C programming language family Concurrent programming languages Free compilers and interpreters Inferno (operating system) Virtual machines