MARC Records

MARC stands for Machine-Readable Cataloging formats.

MARC 21 is the current standard for the representation and communication of bibliographic and related information in machine-readable form. The MARC 21 cataloging format, as well as all official MARC 21 documentation, is maintained by the United States Library of Congress.

The MARC 21 standard uses tags to identify certain data elements in a bibliographic, authority, or holdings record. When a record is referred to as a "MARC record," it means that its variable-length data has been grouped and assigned tags in accordance with the MARC 21 standard. MARC-like records, such as MARC-like patron records, can also be imported into the Innovative database.

Each MARC record has a:

• leader
• directory
  
  The directory is a list of variable-length fields. It contains one 12-byte entry for each field in the record. Each entry consists of the field tag (three bytes), the length of the field (four bytes) and the starting position of the field relative to the base address (five bytes). The first field in the record starts at offset 00000, i.e., the first position after the end of the directory. The directory ends with a field terminator (hex 1E).
  
  Below is an example of a directory:
  
  

  001000900000  005001700009  007001500026  008004100041  028002100082
  040002300103  041001100126  048000900137  100003600146  245005400182
  246004400236  246006100280  246013100341  260003400472  300004000506
  500001700546  500003000563  500009600593  505042800689  511007301117
  650001801190  700004501208  700003701253  700004301290  700003601333
  700003301369  700004501402  710004601447  791002701493  901002801520
  902001101548  999002601559  993001301585  994000801598  910002001606
  994001201626
  

  
  
  The example directory above begins with the numbers "001000900000," which are interpreted as:

  	001		Field tag number (bibliographic record control number)
  	0009		Length of this field (9 bytes)
  	00000		Starting position is the first position after the end of the directory

  
  
  Another portion of the directory reads "245005400182," and is interpreted as:

  	245		Field tag number (bibliographic record title statement)
  	0054		Length of this field (54 bytes)
  	00182		Starting position is 182 positions after the end of the directory

• variable-length data
  
  Variable-length MARC data are identified by a three-digit MARC tag stored in the directory. Each variable field begins with two positions (which can be blanks), followed by a subfield delimiter (hex 1F), a lower-case letter (usually "a") or a number, and the remaining field data. Each field ends with a field terminator (hex 1E). The last character in the record is a record terminator (hex 1D).
  
  Variable-length MARC data can be stored in Innovative database records in either fixed-length or variable-length fields. Where information is stored depends on factors such as the decisions made by your library during implementation of the Innovative database, the load tables used when importing records, and the types of data in a record.

Innovative database variable-length fields are assigned Innovative "field group tags." The Innovative database requires the use of field group tags. MARC tags are optional. If MARC tags are used by your organization, the variable-length fields in your database will have both MARC and field group tags simultaneously. A correspondence between MARC and field group tags is established when your system is set up. For example, a MARC-tagged 090 field may have a c field group tag. You can view the expected correspondence of MARC tags and field group tags for your system by viewing the MARC load table "m2btab.fse".

For proper indexing and record display, the two types of tags must remain in the expected correspondence for each variable-length field in your database.