Erlang is untyped. It has pattern matching syntax, recursion equations, explicit concurrency, asynchronous message passing and is relatively free from side-effects. It supports transparent cross-platform distribution. It has primitives for detecting run-time errors, real-time garbage collection, modules, dynamic code replacement (change code in a continuously running real-time system) and a foreign language interface.
An unsupported free version is available (subject to a non-commercial licence). Commercial versions with support are available from Erlang Systems AB. An interpreter in SICStus Prolog and compilers in C and Erlang are available for several Unix platforms.
Erlang is a unit without dimension, accepted internationally for measuring the traffic intensity. This unit is defined as the aggregate of continuous occupation of a channel for one hour (3600 seconds). An intensity of one Erlang means the channel is continuously occupied.