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Directory (NR)

MARC 21 Authority

October 1999

Indicators and Subfield Codes

No indicators or subfield codes; the data elements are positionally defined.

Character Positions
00-02 - Tag
03-06 - Field length
07-11 - Starting character position

CHARACTER POSITION DEFINITION AND SCOPE

Series of fixed length entries, with one entry for each variable field (control or data) present in a record. Each Directory entry is 12 character positions in length and contains three portions: the field tag, the field length, and the starting character position. The Directory immediately follows the Leader at the beginning of the record and is located at character position 24. The Field length and Starting character position portions of the Directory are defined by Leader/20-23 (Entry map) as being 4 and 5 characters in length, respectively. Because a field tag is always 3 characters, the length of the Tag portion of the Directory is not specified in the Entry map.

More detailed information about the structure of the Directory entries is contained in the MARC 21 Specifications for Record Structure, Character Sets, and Exchange Media.

DESCRIPTION OF A DIRECTORY ENTRY

■ CHARACTER POSITIONS

00-02 - Tag

Three ASCII numeric or alphabetic characters (upper case or lower case, but not both) that identify an associated variable field.

03-06 - Field length

Four ASCII numeric characters that specify the length of the variable field, including indicators, subfield codes, data, and the field terminator associated with the field. A Field length number of less than four digits is right justified and unused positions contain zeros.

07-11 - Starting character position

Five ASCII numeric characters that specify the starting character position of the variable field relative to the Base address of data (Leader/12-16) of the record. A Starting character position number of less than five digits is right justified and unused positions contain zeros.

■ EXAMPLE

	Tag	Field length	Starting character position
Entry 1	001	0013	00000
Entry 2	003	0005	00013
Entry 3	005	0016	00018
Entry 4	008	0041	00034
Entry 5	100	0040	00075

INPUT CONVENTIONS

System-Generated Elements - Each Directory entry is system generated.

Library of Congress >> MARC >> Authority >> Directory

(03/01/2008)