Marc 21 Record Format -- Leader Section

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MARC21 ::= Leader + Record Directory + Variable Fields + X'1B'

Leader ::= Leader1 + Leader2 + Leader3 + Leader4 + Leader5 -- char(24)
Leader1 ::= Logical Record Length + Record Status + Record Type
Leader2 ::= Bibiographic Level + Type of Control + Character Coding Scheme
Leader3 ::= Indicator Count + Subfield Code Count + Base Address of Data
Leader4 ::= Encoding Level + Descriptive Catalog Form + Linked Record Requirement
Leader5 ::= Entry Map

Logical Record Length ::= '99999' -- char(5)

Logical record length, right justified, zero padded

Record Status ::= 'A' | 'C' | 'D' | 'N' | 'P' -- char(1)

Indicates the relation of the record to a file.

Record Type ::= 'A' | 'C' | 'D' | 'E' | 'F' | 'G' | 'I' | 'J' | 'K' | 'M' | 'O' | 'P' | 'R' | 'T' -- char(1)

Indicates the characteristics of and defines the components of the record.

Bibiographic Level ::= 'A' | 'B' | 'C' | 'D' | 'M' | 'S' -- char(1)

Type of Control ::= ' ' | 'A' -- char(1)

Archival or no specific type.

Character Coding Scheme ::= ' ' | 'A' -- char(1)

one-character code that identifies the character coding scheme used in the record. 'A' equals UCS/Unicode, otherwise MARC-8.

Indicator Count ::= '2' -- char(1)

Columns used for indicators, always 2

Subfield Code Count ::= '2' -- char(2)

columns used for subfield codes, always 2

Base Address of Data ::= '99999' -- char(5), right justified, zero padded

indicates the first character position of the first variable control field in a record.

Encoding Level ::= ' ' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | 'U' | 'Z' -- char(1)

Indicates the fullness of the bibliographic information and/or content designation of the MARC record.

Descriptive Catalog Form ::= ' ' | 'A' | 'I' | 'U' -- char(1)

Indicates the descriptive cataloging form reflected in the record.

Linked Record Requirement ::= ' ' | 'R' -- char(1)

A one-character code that indicates whether a note containing basic identification information (i.e., main entry and title, main entry and uniform title, main entry under uniform title, title, uniform title, Standard Technical Report Number, or report number) can be generated from a Linking Entry field (76X-78X).

Entry Map ::= '4500' -- char(4)

Four computer-generated, single-digit numeric characters that indicate the structure of each entry in the Directory.
Col 20 - Length of the length-of-field portion -- Contains a 4
Col 21 - Length of the starting-character-position portion -- Contains a 5
Col 22 - Length of the implementation-defined portion -- Contains a 0
Col 23 - Undefined Entry map character position -- Contains a 0