Appendix P.  Library of Congress Control Number and Library of Congress Card Numbering System  (FN)

Library of Congress Control Number

1.   Basic Structures of the LC Control Number

Library of Congress control numbers assigned beginning in 2001 have a new structure defined in the MARC 21 Format for Bibliographic Data.  The new format includes a four-digit representation of the year the LCCN was assigned.  This enables easier distinction of years in the nineteenth, twentieth, and twenty-first centuries, during which LCCNs have been used.  Like the previously defined MARC LCCN format, the restructured LC control number has twelve character positions; but some other portions of the format have been changed to make room for the four-digit year.  The structure of the new, post-2000 LCCN is as follows:

In the machine-readable LCCN, blank spaces fill the alphabetic prefix positions not used by alphabetic characters.  If no prefix is given, the LCCN begins with two blank spaces.  If a two-character prefix (such as “sn”) is given, the LCCN begins with the prefix and no blank spaces are input.

The number portion of the LCCN may be one to six characters in length.  If the number has fewer than six characters, leading zeroes fill in the positions not used by the number.

The machine-readable LC control number does not include a hyphen, though some representations of the LCCN (such as in field 010 of OCLC records) may use one to separate the year portion from the following number.

The following are examples of LCCNs in the post-2000 machine-readable format:

##2001204501

sn2001058201

LCCNs assigned from 1898 to 2000 and defined in the MARC 21 Format for Bibliographic Data have the following structure:

(As is explained below, under Library of Congress Card Numbering, the "year" portion of LCCNs assigned from December 1968 to January 1972 did not represent a year but consisted of an initial digit "7" followed by a check digit.)

In this format, the alphabetic prefix is left-justified and blank spaces fill the prefix positions not used by alphabetic characters.  If no prefix is given, the LCCN begins with three blank spaces.  A two-character prefix is followed by one blank space; a one-character prefix has two trailing blanks.  The number portion in this format has the same properties (e.g., the use of leading blanks) as in the post-2000 structure.  Likewise, this LCCN format also does not include a hyphen, though other representations may use one.

The supplement number portion of this LCCN structure was defined but never used.  This position is filled by a blank space.

The following are examples of LCCNs in this pre-2001 machine-readable format:

###85645325#

###68004897#

a##62002407#

agr17001177#

sn#99048001#

Because the restructured LCCN could not be implemented before 2001, LCCNs with two-digit years were assigned in 1998, 1999, and 2000, using only numbers not previously used in 1898, 1899, and 1900.  Specific years of assignment may be determined as follows:

Both formats, post-2000 and pre-2001, are valid in MARC; and both are used in CONSER records, according to the format in use when the LCCN was assigned.  LCCNs constructed in one format are never "converted" into the other.  It is possible and correct for LCCNs of different formats to be used in different parts of the same record.  For example, a record may have an LCCN with a four-digit year in subfield $a and LCCNs with two-digit years in subfields $z of the same 010 field.

Earlier forms of LCCN, such as those found on LC printed cards or in the National Union Catalog, are also still valid for retrospective input.  In MARC records, those forms are all represented by the pre-2001 machine-readable LCCN structure shown above.  Different LC card number systems that have been used and may be transcribed retrospectively are described below (see Library of Congress Card Numbering).

2.   Display/Input Form of the LC Control Number in OCLC Field 010

For either format, the form used for display and inputting of LC control numbers in field 010 of records on the OCLC system differs in specific ways from the machine-readable LCCN structure described above.

• In OCLC field 010, the LCCN is left-justified.  If no prefix is given, there are no leading blanks at the beginning of the LCCN.  If a prefix shorter than the prefix portion of the LCCN is given, no trailing blanks are input between the prefix and the year.

• In OCLC field 010, a hyphen is input separating the year from the following number in an LCCN.

• In OCLC field 010, no leading blanks are included in the number portion of the LCCN.  The number occupies as many positions are it has digits.

• In OCLC field 010, no trailing blank is displayed in an LCCN.  If one is input, the OCLC system removes it.

Compare the MARC-defined LCCN structure with the OCLC field 010 display/input form in the following examples:

3.   Suffixes/Alphabetic Identifiers and Revision Dates  [DISCONTINUED]

Suffixes/Alphabetic identifiers

Prior to January 1999, special symbols, called alphabetic identifiers, were appended to control numbers of categories of materials to control the distribution of records and cards to various LC book and card catalogs.  These were input as suffixes, following the control number.  Suffixes and alphabetic identifiers did not affect the uniqueness of the LCCN.

The inclusion of suffixes has been discontinued.  LC has stripped suffixes from field 010 in all records in the LC database; and OCLC will do the same in 2000-2001.  Do not input suffix information in LCCNs anywhere in CONSER records.

Because LCCNs with alphabetic identifier suffixes survive in copies of CONSER and LC records in local databases and in LCCNs in printed sources, there remains some need to be able to recognize such data.  The following identifiers were previously used:

A slash separated the alphabetic identifier from the number portion of the LCCN.

Revision dates

Prior to January 1999, when LC added, changed, or deleted an access point in an LC authenticated record, an indication that a revision was made was given by the addition of a lowercase "r" and the last two digits of the year of the last revision.  If a record was revised more than once, the number of the revision was given after the date of last revision.  The revision date/number was separated from the LCCN by two slashes (one slash if it followed an alphabetic identifier).  Revision dates did not affect the uniqueness of the LCCN.  CONSER members added revision dates to non-pseudo LCCNs when changing pre- AACR2 records to AACR2.

The inclusion of revision data was discontinued in 1999.  Revision information has been deleted from field 010 in all records in the LC database; and OCLC will do the same in 2000-2001.  Do not input revision data in LCCNs anywhere in CONSER records.

Library of Congress Card Numbering

The Library of Congress employed different LC card numbering systems from 1898 to November 1968, from December 1968 to January 1972, and after January 1972.  The length of the LC card number was fixed at twelve characters in all these systems, but the constituent data elements varied.  Details of each are summarized below.

1.   LC Card Numbering System 1898-November 1968

Examples

Prefixes

Numbers in the old system may contain an alphabetic prefix, which is carried in the machine-readable record as lowercase alphabetic characters.  Prefixes can be from one to three characters in length.  Prefixes containing more than three characters have been redefined for use in the machine-readable record as follows:

Suffixes

Numbers in the old system may contain suffixes and/or a revision date.  Such data are carried as variable length data and do not affect the uniqueness of the LC card number.

Suffixes appear below the card number on a printed card on the same slug as the "Library of Congress" legend.  When formerly input into machine-readable form, suffixes were separated from the last numeral of the card number by a slash.  If multiple suffixes occurred, they were separated from one another by a slash.  Suffixes were formerly carried in the MARC record as uppercase characters.

Revision dates

The revision date always consists of at least three characters:  a lowercase "r" followed by two numbers which stand for the last two digits of the year of latest revision (e.g., r69).  The revision date is found in the printing symbol area on the printed card; an area to the right of the hole on the card enclosed in brackets.  When formerly input into MARC format, a revision date, when occurring alone, immediately followed the card number, separated from the last numeral of the number by two slashes.  When occurring in conjunction with suffixes, a revision date immediately followed any suffixes, separated from them by one slash.

2.   LC Card Numbering System December 1968-January 1972

Examples

Prefixes

No alphabetic prefixes are used in the 1968-1972 numbering system.  Numbers in the interim numbering system are distinguished by the initial digit "7", which is followed by a check digit (these two digits take the place of the year portion of the card number in the old system.  The year is not part of the card number but may be determined from the "Date Entered on File" in the MARC record (008/00-05).

Alphabetic identifiers

Information that was expressed by prefixes and suffixes to the card number in the 1898-1968 system is expressed by symbols called "alphabetic identifiers" in the 1968-1972 system.  For example, A (cooperative copy); AC (annotated card); NE (Near East); MAP (map); SA (South Asian).  Such data do not affect the uniqueness of the number and were formerly carried as variable length elements, separated from the last numeral of the card number by a slash.  If multiple alphabetic identifiers occurred, they were separated from one another by a slash.  A revision data, when occurring alone, immediately followed the card number, separated from the last numeral of the number by two slashes.  When occurring in conjunction with any alphabetic identifiers, the revision date was separated by one slash.  Alphabetic identifiers were formerly carried in the MARC record as uppercase characters.  Alphabetic identifiers appear below the card number on a printed card on the same slug as the "Library of Congress" legend.

3.   LC Card Numbering System After January 1972

The structure of the regular LC card numbers in the system after January 1972 is the same as in the 1968-1972 system, with the exception that the last two digits of the year are given as in the 1898-1968 system.

Prefixes

Under the system after January 1972, pseudo LC card numbers, containing a specific two-digit alphabetic prefix, were used on CONSER records authenticated by various CONSER participants.  For more information and examples, see field 010.

See also:

Section F. Appendices