This field is often displayed in a single paragraph at the top of the screen and is usually displayed with mnemonic tags. The field has 40 character positions. That is, a blank is input to represent a coded value. Variable fields Variable fields carry alphanumeric data of variable length. The variable fields carry traditional cataloging data elements.
Variable fields consist of heading fields and descriptive fields.
504 - Bibliography, etc. All subfields are distinct elements within fields. Subfield definitions vary from field to field. The two digits that follow after the tags in a MARC field are called indicators. Each digit position has a certain meaning relating to its particular field and provides computer instructions for processing the data contained in the field.