History of Erlang

Erlang (/ˈɜrlæŋ/ ER-lang) is a general-purpose concurrent, garbage-collected programming language and runtime system. The sequential subset of Erlang is a functional language, with eager evaluation, single assignment, and dynamic typing. It was designed by Ericsson to support distributed, fault-tolerant, soft-real-time, non-stop applications. It supports hot swapping, so that code can be changed without stopping a system.^[3]

While threads require external library support in most languages, Erlang provides language-level features for creating and managing processes with the aim of simplifying concurrent programming. Though all concurrency is explicit in Erlang, processes communicate using message passing instead of shared variables, which removes the need for explicit locks (a locking scheme is still used internally by the VM^[4]).

The first version was developed by Joe Armstrong in 1986.^[5] It was originally a proprietary language within Ericsson, but was released as open source in 1998.

Erlang was designed with the aim of improving the development of telephony applications. The initial version of Erlang was implemented in Prolog and was influenced by the programming language PLEX used in earlier Ericsson exchanges. According to Armstrong, the language went from lab product to real applications following the collapse of the next-generation AXE exchange named AXE-N in 1995. As a result, Erlang was chosen for the next ATM exchange AXD.^[5]

In 1998 Ericsson announced the AXD301 switch, containing over a million lines of Erlang and reported to achieve a reliability of nine "9"s.^[7] Shortly thereafter, Ericsson Radio Systems banned the in-house use of Erlang for new products, citing a preference for non-proprietary languages. The ban caused Armstrong and others to leave Ericsson.^[8] The implementation was open-sourced at the end of the year.^[5] Ericsson eventually lifted the ban; it re-hired Armstrong in 2004.^[8]