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Directory

The record directory consists of a series of fixed-length entries containing the tag, length, and starting character position of each control and variable field in the record. A field terminator ends the record directory. Each entry is 12 bytes.

Directory structure

The following diagram illustrates the structure of a directory entry:

00-02 03-06 07-11
Tag Field Length Starting Character Position

Directory elements

Each variable field in bibliographic and authority records has the following elements:
 

element description
Tag
  • Positions 00-02
  • Three-character number that identifies an associated variable field
Field Length
  • Positions 03-06
  • Four-character number that specifies the length of the variable field to which the entry corresponds
  • Equal to the sum of the length of the indicators, subfield codes, data, and the field terminator associated with the field
  • If fewer than four digits, right justified with leading zeros
Starting Character Position
  • Positions 07-11
  • Five-character number that specifies the starting character position of the variable field to which the entry corresponds relative to the base address of the data of the record
  • If fewer than five digits, right justified with leading zeros

 

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