Each communications system contains a similar ASN.1 encoding/decoding scheme written in the language used on that particular system. When one system wants to send data to another, the first system encodes the data into ASN.1, sends the data, and the second system receives and decodes the data using the decoder written in the langauge used on that system.

ASN.1 is an ISO /ITU standard based on the OSI model. It was first defined in 1984 as part of CCITT X.409; revised in 1995; then became its own standard, X.208, in 1998.

ASN.1 Overview
Provides overview of ASN.1 and discusses its many current uses.

ASN.1: The Tutorial and Reference
Breaks down and explains the structure and rules of ASN.1. Provides a diagram and examples.