Directory (NR)
MARC 21 Community Information
January 2000
Indicators and Subfield Codes
Has 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
Computer-generated index to the location of the variable control and data fields within
a record. The Directory immediately follows the Leader at character position 24 and
consists of a series of fixed-length (12 character positions) entries that give the tag,
length, and starting character position of each variable field.
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 ASCII alphabetic characters (uppercase or lowercase, 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 to
which the entry corresponds. This length includes the 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 |
0004 |
00013 |
| Entry 3 |
005 |
0017 |
00017 |
| Entry 4 |
008 |
0016 |
00034 |
| Entry 5 |
040 |
0013 |
00050 |
INPUT CONVENTIONS
System-Generated Elements - Each Directory entry is system generated.