Structure of the LC Control Number

Network Development and MARC Standards Office
Library of Congress

The LC control numbering system has had the same basic structure since its initial use to control Library of Congress bibliographic information in card form beginning in 1898 (LCCN structure A). On January 1, 2001, a structural change will occur (LCCN structure B). The basic control number has been fixed in length at 12 characters and will remain that length, although under LCCN structure A suffixes were occasionally used and under LCCN structure B the location of element parts is slightly altered to accommodate a four digit year. Under both structures, the prefix, year, and serial number are the basic elements required to make a LCCN unique.

LCCN Structure A (1898-2000)

Name of Element Number of characters Character position in field
Alphabetic Prefix 3 00-02
Year 2 03-04
Serial Number 6 05-10
Supplement Number 1 11
Suffix / Alphabetic Identifier variable 12-n
Revision Date variable 12-n

LCCN Structure B (2001- )

Name of Element Number of characters Character position in field
Alphabetic Prefix 2 00-01
Year 4 02-05
Serial Number 6 06-11

Alphabetic prefix

Prefixes are carried in a MARC record as lowercase alphabetic characters and serve to differentiate between different series of LC control numbers. Prefixes are left justified and unused positions contain blanks. If no prefix is present, the prefix portion contains blanks.

Authority Record Prefixes

The following alphabetic prefixes have been established by the Library of Congress for Authority records. They are used in both LCCN Structures A and B.

MARC prefix Explanation of usage
n Name or subject authority record keyed by LC
nb Name or subject authority record originating in the British Library
nr Name or subject authority record originating in the Research Libraries Information Network (RLIN)
no Name or subject authority record originating in the Online Computer Library Center (OCLC)
sh LCSH subject authority record distributed by LC
sj Juvenile subject authority keyed by LC and distributed in the LC Annotated Children's Cataloging Program
sp Subject authority proposal record in the LC catalog. (When it is approved, the record will be distributed with the prefix sh.)
    010 ##$an##79051955#
        [LCCN structure A; number on printed card: n79-51955]
    010 ##$an#2001050268
        [LCCN structure B; number in print form: n2001-50284]

Bibliographic Record Prefixes [Structure A Only]

The following alphabetic prefixes were formally used by the Library of Congress for Bibliographic records. Since they were used in records before 2001, they are found in LCCN Structure A only.

Prior to the existence of MARC records, prefixes of various lengths were used on printed cards with combinations of uppercase or lowercase letters and numbers. For MARC records, equivalents have been defined by the Library of Congress for some of these early prefixes. The second column in the list below gives prefixes found on printed cards not printed from machine-readable records and shows how they are to be input into a MARC version of the record. Only card prefixes which have a MARC form noted below should be recorded in machine-readable records.

MARC
Prefix		 Prefix
on card		 Explanation of usage
a A Cataloging provided to LC by an American library, 1909-
ac AC Cataloging for foreign materials provided to LC by cooperating libraries under the auspices of the ALA Committee on Cooperative Cataloging, 1932-1942
ac AC Annotated cards for juvenile books, 1966-
af AF Cataloging for foreign acquisitions provided to LC by other American libraries, 1946-1950.
afl AFLM No explanation available
agr Agr U.S. Department of Agriculture cataloging, 1902-
bi   Handbook of Latin American Studies record
br BR Library of Congress, Division for the Blind, Braille book
bs BS U.S. Bureau of Standards cataloging, 1913-1938.
c C U.S. Interstate Commerce Commission cataloging, 1915-1916
c C Library of Congress, Chinese entries, 1949-
c C-245
or 245		 LC card numbers for June-August 1898. Year prefix "98" added when input into MARC
ca CA LC temporary entries for books in the general classified collections, 1905-1937
cad CA Dupl LC temporary entries for books in the general classified collections, 1905-1937
cd CD LC analytical entries for sets and series prepared by the Card Division, 1916-1940
cd CD Cataloging prepared for LC card sales
clc   Collection level cataloging; PREMARC record
cs CS Cataloging prepared by the LC Cooperative Cataloging and Classification Service, 1934-1939
cx CX Cross reference cards used in LC catalogs for Chinese entries, 1958-
cy   Federal Cylinder Project, Oct. 1980
d 1-D-245
or D-245		 LC card numbers for May-December 1901. Year prefix "01" added when input into MARC
do DO U.S. Superintendent of Docs. cataloging, 1913-1916
e E U.S. Office of Education cataloging, 1908-1958
es ES U.S. Engineers School cataloging, 1913-1935
f F U.S. Bureau of Fisheries cataloging, 1910-1940
f 1-F-245
or F-245		 LC card numbers for May-December 1901. Year prefix "01" added when input into MARC
fi Fi Films cataloged by LC, 1951-
fia FiA Cataloging provided by film producers, 1951-
fie FiE Cataloging provided by the Visual Education Service of the Office of Education, and other government agencies, 1951-
g 1-G-245
or G-245		 LC card numbers for May-December 1901. Year prefix "01" added when input into MARC
gm GM Maps cataloged by LC, 1968-1972
gs GS U.S. Geological Survey cataloging, 1904-
h H U.S. National Institute of Health cataloging, 1914-1921
ha HA U.S. Housing Authority cataloging, 1940-
he HE Hebrew entries cataloged by LC, 1964-
hew HEW U.S. Dept. of Health, Ed., and Welfare cataloging, 1958-
hex HEX Cross reference cards used for Hebrew entries, 1964-
it 1-I-245
or It-245		 LC card numbers for May-December 1901. Year prefix "01" added when input into MARC
int Int U.S. Department of the Interior cataloging, 1959
j J LC cataloging for Japanese materials 1949-
ja JA Cataloging for Japanese materials provided to LC by other American libraries, 1951
jx JX Cross reference cards used for Japanese entries, 1958-
k K Korean entries cataloged by LC, 1951-
kx KX Cross reference cards used for Korean entries, 1958-
l L U.S. Dept. of Labor cataloging, 1911-
llh   Index to Hispanic Legislation cataloging
ltf   Less-than-full cataloging; PREMARC record
m M Sheet music cataloged by LC, 1953-1962
ma MA Sheet music for which copy was supplied by another American library, 1953-1961
map Map Atlases in the Maps Division of LC, 1901-
map 1-Map-50
or Map-50		 LC card numbers for maps for period May-December 1901. Year prefix "01" added when input into MARC
med Med U.S. Armed Forces Medical Library cataloging, 1946-1948
mic Mic Microfilms cataloged by LC, 1949-
mid MicA Microfilms for which cataloging was provided by another American library, 1946-
mie Micp Microcards and microprints cataloged by LC, 1953-
mif MicpA Microcards and microprints for which cataloging was provided by another American library, 1953-
mm   Library of Congress Manuscript Division
mp   Early films cataloged by LC, 1970s
mpa MPA Pan American Union cataloging for sheet music, 1956-
ms MS Manuscripts cataloged by LC, 1959-
mus 1-Music-245
or
Music-245		 LC card numbers for music for May-December 1901. Year prefix "01" added when input into MARC
ncn   Nitrate Film Service cataloging
ne NE Materials published in the Near East or in the languages of those countries, 1961-
nex NEX Cross reference cards used for books published in the Near East or in the languages of those countries, 1961-
no NO U.S. Naval Observatory cataloging, 1930-1940
ntc   National Translation Center cataloging
nuc   Records printed in the National Union Catalog for which no LC card number is available
or   Order Division cataloging
pa PA Pan American Union cataloging, 1930-
pho Pho Cataloging provided by other libraries for photographic reproductions of books, 1927-
php PhoM Cataloging provided by Card Division for photographic facsimiles issued by the Modern Language Association of America, 1927-1938
phq PhomA Cataloging provided by other libraries for Modern Language Association of America photographic facsimiles
po PO U.S. Patent Office cataloging, 1917-1953
pp   Prints and Photographs videodisc system, March 1984
r R Photograph records cataloged by LC, 1953-
ra RA Cataloging provided by other American libraries for photographs, 1955-
rc 1-Rc-245
or Rc-245		 LC card numbers for May-December 1901. Year prefix "01" added when input into MARC
re   Cataloging for commercial ethnic sound recordings produced in the U.S. project, 1981
ru   Cataloging from the Russian Book Chamber, 1988-
s S Smithsonian Institution cataloging, 1913-
sa SA Cataloging for materials published in Southeast Asia or in the languages of those countries, 1961-
sax SAX Cross reference cards used for materials published in Southeast Asia or in the languages of those countries, 1961-
sc   Serials, CONSER item not in LC
sd SD U.S. Dept. of State cataloging, 1914-
sf   Serials form card or Minimal Level Cataloging or classed separately monographic series
sg SG Surgeon General's Library, U.S. Army cataloging, 1916-
sn   Serials, CONSER, item may or may not be in LC
ss SS Social Security Administration cataloging, 1944-1958
su   Split manuscript records
tb TB Talking Books program cataloging
tmp   Temporary cataloging from PREMARC
um   Union map; an outside map record input by the Geography and Map Division for NUC use but residing in the G&M database
unk   Card for which no LC card number was available; PREMARC
w W District of Columbia Public Library cataloging, 1905-1942
war War U.S. Army, War College cataloging, 1907-1932
x X Cross reference cards used in LC catalogs, January 1941-
z 1-Z-245
or Z-245		 LC card numbers for May-December 1901. Year prefix "01" added when input into MARC
    010 ##$a###68004897#
        [LCCN structure A; number on printed card: 68-4897]
    010 ##$a##2001045944
        [LCCN structure B; number in print form: 2001-45944]

Classification Record Prefixes
The following alphabetic prefixes have been established by the Library of Congress for Classification records. They are used in both LCCN Structures A and B.

MARC prefix: Explanation of usage
cf Classification record keyed by LC
ct Table record keyed by LC
    010 ##$acf#97051955#
        [LCCN structure A; number on printed card: cf97-51955]
    010 ##$acf2001050268
        [LCCN structure B; number in print form: cf2001-50268]
Holdings and Community Information Record Prefixes
The alphabetic prefix portion contains blanks.

Year

Authority Records
For control numbers assigned under LCCN structure A, the year portion consists of two digits representing the year the control number was assigned. In name authority records that were converted retrospectively by an agency under contract to LC, the digits 50 were used for the year for name authority records, and the digits 42 were used for series authority records. In subject authority records that were converted retrospectively from an LC internal format to MARC, the digits 85 were used instead of the actual year of creation.

For control numbers assigned under the LCCN structure B beginning with the year 2001, the year portion consists of four digits.

Bibliographic Records
For control numbers assigned under LCCN structure A, the year portion consists of two digits representing the year the control number was assigned. In most numbers, the year portion reflects the year in which the LC control number was assigned to the record for the bibliographic item. During the 1969-1972 period, a 7-series year number was assigned. In these numbers the initial digit of 7 was followed by a modulus-ll check digit. The year in which the card number was assigned can be approximated from the year portion of the Date entered on file (008/00-05). With the re-institution of the year series number in 1972, provisions were made to skip those individual card numbers which could have been assigned previously as a 7-series number. Note: 7-series numbers were not used for non-book map material. The prefix gm was used from 1968 through 1972.

For control numbers assigned under the LCCN structure B beginning with the year 2001, the year portion consists of four digits.

For LC control numbers with two-digit years, the century may be determined according to the following table:

2-digit year Sequential number Century Sequential number Century
98 Less than 3000 18 3000 or greater 19
99 Less than 6000 18 6000 or greater 19
00 Less than 8000 19 8000 or greater 20

Classification, Holdings and Community Information Records
For control numbers assigned under LCCN structure A, the year portion consists of two digits normally representing the year the record was created.

For control numbers assigned under LCCN structure B beginning with the year 2001, the year portion consists of four digits.

Serial number (All Formats)

The serial number portion consists of one to six digits. Serial numbers of less than six digits are right justified and unused positions contain zeros. The hyphen which separates the year and the serial number on LC displays and printed products is not carried in the MARC record. For example, the number 85-2 is carried as 85000002 in a record.

Supplement number (All Formats) [Structure A Only]

This character position was originally defined to carry a supplement number for dashed-on supplement entries in bibliographic records. Use of the supplement number was not implemented for bibliographic, authority, classification, holdings and community information records, therefore this position contains a blank in all LCCN Structure A identifiers.

Suffix/Alphabetic Identifier (Bibliographic Records only) [Structure A Only]

Older LC control numbers sometimes include suffixes or alphabetic identifiers carried as variable length data following the Supplement number. A single slash (/) introduces the suffix/alphabetic identifier. Multiple occurrences of either suffixes or alphabetic identifiers are separated one from the other by a slash. Suffixes and alphabetic identifiers do not affect the uniqueness of the control number.

All suffixes and alphabetic identifiers, except the revision date, appear in the MARC record as uppercase alphabetic characters. On printed card copy, suffixes appear after the LC control number separated by a slash. Suffixes have not been assigned since 1969 and they will be deleted from Library of Congress files in 1999. Alphabetic identifiers appear on printed card copy as uppercase alphabetic characters beneath the LC card number in the lower right hand corner of the card. Alphabetic identifiers were first assigned in 1969 and were used as distribution information for card copy by LC. Alphabetic identifiers were deleted from the Library of Congress files in 1999.

    010 ##$a###79139101#/AC/MN
        [Printed number is 79-139101 with AC MN printed below the number.]
    010 ##$a###65077628#/MN
        [Printed number is 65-77628 with MN printed below the number.]
Suffix/alphabetic identifiers

AC used on records included in the "Annotated Card" program
AM used for works in Amharic
ACN used for works in Chinese
AJ used for works in Japanese
AK used for works in Korean
F used for records created by the Audiovisual Section, Special Materials Cataloging Division for motion pictures, filmstrips, sets of slides and transparencies, video recordings, etc.
HE used for works published in the Hebrew alphabet, regardless of language
M used for works classed in M
MAP used for atlases
MN used for works classed in ML and MT
MP used for records created by the Motion Picture, Broadcasting and Recorded Sound Division
NE used for works in Armenian, Arabic, Georgian, Ottoman Turkish, Persian, Pashto, and Turkish, as well as any non-Slavic language of Central Asia written in the Cyrillic alphabet
PP used for records created by the Prints and Photographs Division
R used for all sound recordings

Revision Date (Bibliographic Records only) [Structure A Only]

The revision date associated with LC control numbers specified the latest date that the bibliographic data in a record underwent a change. Revision data do not affect the uniqueness of the control number. To account for the number of times significant changes have been made to a record beyond the first such change, a number was added as the last character of the revision date. The date a record was originally created is the Date entered on file (field 008/00-05).

A revision date such as "r73" means that the record was changed in 1973. The revision date "r743" means that significant changes have been made to the record three times, the last being made in 1974.

    010 ##$a###75425165#//r75
        [Number 75-425165 revised in 1975.]

    010 ##$a###73002284#//r752
        [Number 73-2284 with [r75]rev 2 printed revision information.]

    010 ##$a###58062665#/L/r58
        [Printed number is 58-62665 rev. (The * was represented on the printed product by a double dagger and indicates limited cataloging; it was carried in the MARC record as an L. When the LC control number was printed from the MARC record, the L printed as Lim beneath the control number.]
The revision date was used as an indication of the degree of importance of a change made to a record. A significant change to a record at the Library of Congress was defined as one important enough to warrant, among other things, redistribution of cards to LC's own catalogs. A significant change included changes to content designation, to an access point (fields 020, $a or $z, 028, $a, 050, 051, 082, 1XX, 240, 245 #a, 4XX (excluding 490), 6XX, 7XX, 8XX), a change to the extent of an item (300 #a), a change to the publication date (260 #c), a change to the record control number (field 001), or a change to Leader/18 (Descriptive cataloging form).

Revision information was separated from a suffix or an alphabetic identifier by one slash (/). If no suffixes or alphabetic identifiers are present, revision information was separated from the Supplement number by two slashes (//). The inclusion of revision data was discontinued in 1999 and deleted from all records in the Library of Congress files.


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