In OCLC cataloging interfaces the Leader and the 005 and 008 variable control fields are displayed as a single area with mnemonic labels for each element, called the fixed field. Users have the option to display the fixed field as separate fields in Connexion client and WorldShare Record Manager.
The variable control fields (005, 006, 007, 008) do not have indicators or subfield codes. OCLC uses subfield codes in 007 field displays to assist with readability and editing. The subfield codes are not included in electronic versions of the record.
Variable data fields will vary in number, and in length. Each variable field can have between 1 and 9,999 characters. They are identified by the following information:
Tag: a 3-digit numeric value coded 010 through 999
Indicators: 2 positions, coded with blank or 0 through 9 as possible values
Subfields: A textual element identified by a delimiter (‡) and a lowercase alphabetic or numeric code