"Abstract Syntax Notation" in ITU-T X.680 ; also note related language specifications . These are all reference materials, largely opaque to humans; we need to mention here also such tutorials as Milan and Dubuisson's  and Kaliski's ".. Layman's Guide ..." .
X.509v3 Certificate Viewer example based on the tcllib asn package
ASN.1 is commonly used in the following applications
- Cryptography related file formats (X509 certificates, PKCS#7 messages) etc.
- Telecommunications systems like Bluetooth, H232, UMTS etc.
- Library catalogue systems based on the Z39.50 protocol, see Yaz