Lecture 15: ASN.1 and BER Intro

Digression on ASN.1 Syntax Conventions

In writing ASN.1 specifications, the case of the characters used conventionally indicates to a human reader the part of the ASN.1 grammar in use. Thus:

A type in ASN.1 is indicated by starting its name with an uppercase letter, eg: Gauge.
for a value (an instance of a type), the word starts with a lowercase letter, eg internet.
The keywords of the ASN.1 language, and macros, are written entirely in uppercase, eg OCTET STRING

Note that in these notes, an attempt will also be made to present all ASN.1 (and other) syntactic elements in the fixed-width courier typeface. Occasional lapses from this convention may have to be forgiven by the reader...

Example:

MyType ::= TYPE
nameOfValue MyType ::= VALUE

Note also that, where appropriate, we adopt the OSI convention of referring to "octets", instead of "bytes", even though the terms have almost universally identical meaning.

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