Editing Erlang (programming language) (section)

==History==
The name ''Erlang'', attributed to Bjarne Däcker, has been presumed by those working on the telephony switches (for whom the language was designed) to be a reference to Danish mathematician and engineer [[Agner Krarup Erlang]] and a [[Abbreviation#Syllabic abbreviation|syllabic abbreviation]] of "Ericsson Language".<ref name="hopl"/><ref>{{cite web |url=http://www.erlang.org/pipermail/erlang-questions/1999-February/000098.html |title=Erlang, the mathematician? |date=February 1999 }}</ref><ref>{{cite web |url=https://foldoc.org/Erlang |title=Free Online Dictionary of Computing: Erlang }}</ref> Erlang was designed with the aim of improving the development of telephony applications.<ref>{{cite web|url=http://erlang.org/course/history.html|title=History of Erlang|website=Erlang.org}}</ref> The initial version of Erlang was implemented in [[Prolog]] and was influenced by the programming language [[PLEX (programming language)|PLEX]] used in earlier Ericsson exchanges. By 1988 Erlang had proven that it was suitable for prototyping telephone exchanges, but the Prolog interpreter was far too slow. One group within Ericsson estimated that it would need to be 40 times faster to be suitable for production use. In 1992, work began on the [[BEAM (Erlang virtual machine)|BEAM]] virtual machine (VM), which compiles Erlang to C using a mix of natively compiled code and [[threaded code]] to strike a balance between performance and disk space.<ref>{{cite book |last=Armstrong |first=Joe |chapter=The development of Erlang |title=Proceedings of the second ACM SIGPLAN international conference on Functional programming |journal=ACM SIGPLAN Notices |date=August 1997 |volume=32 |issue=8 |pages=196–203 |doi=10.1145/258948.258967 |isbn=0897919181 |s2cid=6821037 }}</ref> According to co-inventor Joe Armstrong, the language went from laboratory product to real applications following the collapse of the next-generation [[AXE telephone exchange]] named [[:sv:AXE-N|''AXE-N'']] in 1995. As a result, Erlang was chosen for the next [[Asynchronous Transfer Mode]] (ATM) exchange ''AXD''.<ref name="hopl"/>

[[File:Robert Virding and Joe Armstrong, 2013.jpg|thumb|Robert Virding and Joe Armstrong, 2013]]
In February 1998, Ericsson Radio Systems banned the in-house use of Erlang for new products, citing a preference for non-proprietary languages.<ref>{{cite thesis|url=https://cogsys.uni-bamberg.de/team/schmid/uoshp/lehreuos/fp01-www/fp-referate/erlang/bjarnelic.pdf#page=45|title=Concurrent Functional Programming for Telecommunications: A Case Study of Technology Introduction|first=Bjarne|last=Däcker|date=October 2000|publisher=Royal Institute of Technology|page=37}}</ref> The ban caused Armstrong and others to make plans to leave Ericsson.<ref name="questions"/> In March 1998 Ericsson announced the AXD301 switch,<ref name="hopl"/> containing over a million lines of Erlang and reported to achieve a [[high availability]] of [[nines (engineering)|nine "9"s]].<ref>
{{cite web |url=http://www.rabbitmq.com/resources/armstrong.pdf |title=Concurrency Oriented Programming in Erlang |date=9 November 2002}}
</ref> In December 1998, the implementation of Erlang was open-sourced and most of the Erlang team resigned to form a new company, Bluetail AB.<ref name="hopl"/> Ericsson eventually relaxed the ban and re-hired Armstrong in 2004.<ref name="questions">{{cite web |url=http://erlang.org/pipermail/erlang-questions/2006-July/021368.html |title=question about Erlang's future |date=6 July 2010}}</ref>

In 2006, native [[symmetric multiprocessing]] support was added to the runtime system and VM.<ref name="hopl"/>

===Processes===
Erlang applications are built of very lightweight Erlang processes in the Erlang runtime system. Erlang processes can be seen as "living" objects ([[object-oriented programming]]), with data encapsulation and [[message passing]], but capable of changing behavior during runtime. The Erlang runtime system provides strict [[process isolation]] between Erlang processes (this includes data and garbage collection, separated individually by each Erlang process) and transparent communication between processes (see [[Location transparency]]) on different Erlang nodes (on different hosts).

Joe Armstrong, co-inventor of Erlang, summarized the principles of processes in his [[Doctor of Philosophy|PhD]] [[thesis]]:<ref>{{Cite thesis |last=Armstrong |first=Joe |title=Making reliable distributed systems in the presence of software errors |date=20 November 2003 |degree=DTech |publisher=The Royal Institute of Technology |place=Stockholm, Sweden}}</ref>

*Everything is a process.
*Processes are strongly isolated.
*Process creation and destruction is a lightweight operation.
*Message passing is the only way for processes to interact.
*Processes have unique names.
*If you know the name of a process you can send it a message.
*Processes share no resources.
*Error handling is non-local.
*Processes do what they are supposed to do or fail.

Joe Armstrong remarked in an interview with Rackspace in 2013: "If [[Java (programming language)|Java]] is '[[write once, run anywhere]]', then Erlang is 'write once, run forever'."<ref>{{cite AV media |last=McGreggor |first=Duncan |date=26 March 2013 |title=Rackspace takes a look at the Erlang programming language for distributed computing |medium=Video |language=en |url=https://www.youtube.com/watch?v=u41GEwIq2mE&t=3m59s | archive-url=https://ghostarchive.org/varchive/youtube/20211211/u41GEwIq2mE| archive-date=2021-12-11 | url-status=live|publisher=Rackspace Studios, SFO |access-date=24 April 2019}}{{cbignore}}</ref>

===Usage===
In 2014, [[Ericsson]] reported Erlang was being used in its support nodes, and in [[GPRS]], [[3G]] and [[LTE (telecommunication)|LTE]] mobile networks worldwide and also by [[Nortel]] and [[Deutsche Telekom]].<ref>{{cite web |url=http://www.ericsson.com/news/141204-inside-erlang-creator-joe-armstrong-tells-his-story_244099435_c |title=Ericsson |work=Ericsson.com |date=4 December 2014 |access-date=7 April 2018}}</ref>

Erlang is used in [[RabbitMQ]]. As [[Tim Bray]], director of Web Technologies at [[Sun Microsystems]], expressed in his keynote at [[O'Reilly Open Source Convention]] (OSCON) in July 2008:
{{Blockquote|If somebody came to me and wanted to pay me a lot of money to build a large scale message handling system that really had to be up all the time, could never afford to go down for years at a time, I would unhesitatingly choose Erlang to build it in.}}

Erlang is the programming language used to code [[WhatsApp]].<ref>{{cite web |url=https://www.fastcompany.com/3026758/inside-erlang-the-rare-programming-language-behind-whatsapps-success |title=Inside Erlang, The Rare Programming Language Behind WhatsApp's Success |work=fastcompany.com |date=21 February 2014 |access-date=12 November 2019}}</ref>

It is also the language of choice for [[Ejabberd]] – an [[XMPP]] messaging server.

[[Elixir (programming language)|Elixir]] is a programming language that compiles into BEAM byte code (via Erlang Abstract Format).<ref>{{Cite web |title=Erlang/Elixir Syntax: A Crash Course |url=https://elixir-lang.org/crash-course.html |access-date=2022-10-10 |website=elixir-lang.github.com |language=en}}</ref>

Since being released as open source, Erlang has been spreading beyond telecoms, establishing itself in other vertical markets such as FinTech, gaming, healthcare, automotive, Internet of Things and blockchain. Apart from WhatsApp, there are other companies listed as Erlang's success stories, including [[Vocalink]] (a MasterCard company), [[Goldman Sachs]], [[Nintendo]], AdRoll, [[Grindr]], [[BT Mobile]], [[Samsung]], [[OpenX (company)|OpenX]], and [[SITA (business services company)|SITA]].<ref>{{cite web |url=https://www.erlang-solutions.com/blog/which-companies-are-using-erlang-and-why-mytopdogstatus.html |title=Which companies are using Erlang, and why? #MyTopdogStatus |work=erlang-solutions.com |date=11 September 2019 |access-date=15 March 2020}}</ref><ref>{{Cite web |url=https://www.erlang-solutions.com/blog/which-new-companies-are-using-erlang-and-elixir-mytopdogstatus.html |title=Which new companies are using Erlang and Elixir? #MyTopdogStatus |website=erlang-solutions.com |date=2 March 2020 | access-date=2020-06-24}}</ref>