Describes a notation for abstract syntax definition called Abstract Syntax Notation One, and defines a number of simple types, with their tags, and specifies a notation for referencing these types and for specifying values of these types. Gives mechanisms for constructing new types from more basic types, and specifies a notation for defining such structured types and assigning them tags, and for specifying values of these types. The ASN.1 notation can be used whenever it is necessary to define the abstract syntax of information. It is particularly, but not exclusively, applicable to application protocols, but is also referenced by other presentation layer standards which define encoding rules for the simple types, the structured types, the character string types and the useful types defined.