The control and variable fields consist of variable-length alphanumeric data. They may differ in content for each type of MARC record.
Subfield delimiters and codes separate alphanumeric data within variable fields. No spaces appear before and after subfield delimiters and codes.
All fields end with a field terminator. A field terminator code and a record terminator code follow the last field.
Control fields in MARC 21 formats are assigned tags that begin with two zeros.
- They contain data and a field delimiter
- They do not contain indicators or subfield codes
- The control number field is assigned tag 001 and contains the control number of the record
- Each record contains only one control number field (with tag 001), which is located at the base address of data
Variable fields in MARC 21 formats are assigned tags which are ASCII numeric characters and which do not begin with two zeros.
- Such fields contain indicators and subfield codes, as well as data and a field terminator
- The number, length, or content other than that already stated or implied, for example, those resulting from the limitation of total record length, if not restricted
Variable field components
Each variable field in a bibliographic or authority record has the following components:
|Indicator 1 and 2||