o The field name you assign can be up to 31 characters from the set A-Z, 0-9, _, and $. The first character must be a letter from A-Z, and the last character can not be _ or $. You can use 8-bit alphabetic characters in field names. o If you use an asterisk (*) instead of a field-name, you create an unnamed field. o If you do not specify a data type for the STRUCTURE, the CDDL assigns it the UNSPECIFIED data type. o Subordinate field description statements describe contiguous portions of the field described by the STRUCTURE. o There must be at least one subordinate field description statement. A subordinate field can be an elementary, a STRUCTURE, a COPY, or a VARIANTS field. o CDDL accepts the keyword GROUP as a synonym for STRUCTURE, but the compiler issues a warning when you use GROUP. o You must terminate the STRUCTURE and the END statements with periods.