External Interfaces - Erlang has a

External Interfaces - Erlang has a "port" mechanism which allows processes to communicate wite the outside world in a manner which is semantically equivatent to internal message passing between Erlang processes. This mechanism is used for communication with the host operating system and for interaction with other processes (perhaps written in other languages) which run on the host operating system. lf required for reasons of efficiency a special version of the "port" concept allows other software to be directly linked into the abstract machine. Examples of the use of the port mechanism are interacting with the host file system interfacing to a graphical interface and a low level socket interface.