Limbo is a

programming language A programming language is a system of notation for writing computer programs. Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...

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 ...

for the Inferno operating system. It was designed at

Bell Labs Nokia Bell Labs, commonly referred to as ''Bell Labs'', is an American industrial research and development company owned by Finnish technology company Nokia. With headquarters located in Murray Hill, New Jersey, Murray Hill, New Jersey, the compa ...

Sean Dorward Sean, also spelled Seán or Séan in Hiberno-English, is a male given name of Irish origin. It comes from the Irish versions of the Biblical Hebrew name '' Yohanan'' (), Seán ( anglicized as '' Shaun/ Shawn/ Shon'') and Séan (Ulster variant; a ...

, Phil Winterbottom, and

Rob Pike Robert Pike (born 1956) is a Canadian programmer and author. He is best known for his work on the Go programming language while working at Google and the Plan 9 operating system while working at Bell Labs, where he was a member of the Unix t ...

. The Limbo

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

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 construction, constructi ...

-independent

object code In computing, object code or object module is the product of an assembler or compiler In computing, a compiler is a computer program that Translator (computing), translates computer code written in one programming language (the ''source'' ...

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. Limbo's approach to concurrency was inspired by

Hoare Hoare is an English surname derived from Middle English '' hor(e)'' meaning grey- or white-haired. Notable people with the surname include: * Albert Alfred Hoare, known as Bert Hoare (1874–1962), South Australian politician * Bertie Hoare (19 ...

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 p ...

(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 (programming language), C language, but its approach to concurr ...

language and Winterbottom's

Alef Aleph (or alef or alif, transliterated ʾ) is the first letter of the Semitic abjads, including Phoenician ''ʾālep'' 𐤀, Hebrew ''ʾālef'' , Aramaic ''ʾālap'' 𐡀, Syriac ''ʾālap̄'' ܐ, Arabic ''ʾalif'' , and North Arabian 𐪑 ...

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 or "concern" of the d ...

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"), a ...

* 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'' (for example, integer, floating point, string) to every '' term'' (a word, phrase, or other set of symbols). Usu ...

at compile and run-time *

interprocess communication In computer science, interprocess communication (IPC) is the sharing of data between running processes in a computer system. Mechanisms for IPC may be provided by an operating system. Applications which use IPC are often categorized as clients ...

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 ...

* simple

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

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 '' ...

, 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, refere ...

and a

real-time Real-time, realtime, or real time may refer to: Computing * Real-time computing, hardware and software systems subject to a specified time constraint * Real-time clock, a computer clock that keeps track of the current time * Real-time Control Syst ...

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 developed by AT&T Corporation in the early 1990s. It was based on the company's CRISP (C-language Reduced Instruction Set Processor) design resembling the classic RISC pipeline, and which in turn grew ou ...

microprocessor, as used in the original

BeBox The BeBox is a discontinued personal computer from Be Inc., running the company's operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), s ...

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 January 30, 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 ...

The Limbo Programming Language
by Dennis M. Ritchie 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) Concurrent programming languages Free and open source compilers Inferno (operating system) Programming languages created in 1995 Virtual machines