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MARC-8

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The MARC-8 charset is a MARC standard used in MARC-21 library records.[1] The MARC formats are standards for the representation and communication of bibliographic and related information in machine-readable form, and they are frequently used in library database systems. The character encoding now known as MARC-8 was introduced in 1968 as part of the MARC format. Originally based on the Latin alphabet, from 1979 to 1983 the JACKPHY initiative expanded the repertoire to include Japanese, Arabic, Chinese, and Hebrew characters (among others), with the later addition of Cyrillic and Greek scripts. If a character is not representable in MARC-8 of a MARC-21 record, then UTF-8 must be used instead. UTF-8 has support for many more characters than MARC-8, which is rarely used outside library data.

Technical details

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MARC-8 uses a variant of the ISO-2022 encoding. It uses escape characters to represent characters beyond the 7-bit ASCII range of characters.

It generally uses the same logical BiDi ordering as Unicode.

The combining characters and base characters are in a different order than used in Unicode. The following are some examples. The combining characters are not always stored in reverse order as Unicode normalization. The MARC-21 standard describes the MARC-8 Unicode conversion issues in more detail.

Displayed

Character

Unicode

NFD

MARC-8
á a  ́   ́ a
ậ a   ̣   ̂   ̂   ̣ a

Code structure

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The ISO/IEC 2022 coding specifies a two-layer mapping between character codes and displayed characters. In MARC-8, character codes from the 7-bit ASCII graphic range (0x20–0x7F) are referred to as "G0" codes, while codes from the "high ASCII" range (0xA0–0xFF) are referred to as the "G1" codes. Graphic character sets are designated and invoked by means of a multiple byte escape sequence consisting of the escape character, an Intermediate character sequence, and a Final character in the form ESC I F.

The following table shows the intermediate byte after the ESC byte (hexadecimal 1B), and the corresponding ASCII characters.

Intermediate Bytes[2]
G0 set G1 set
SBCS MBCS SBCS MBCS
Normal ISO-2022 28 ( 24 $ 29 ) 24 29 $)
Alternate ISO-2022 (additional 63+16 sets) 2C , 24 2C $, 2D - 24 2D $-

The following table shows the final bytes in hexadecimal and the corresponding ASCII characters after the intermediate bytes.

Final Bytes[2]
Bytes Characters Name Type Comment
31 1 Chinese, Japanese, Korean (EACC) MBCS
32 2 Basic Hebrew SBCS
33 3 Basic Arabic SBCS
34 4 Extended Arabic SBCS
42 B Basic Latin (ASCII) SBCS
21 45 !E Extended Latin (ANSEL) SBCS The 21(hex) technically is a second byte of the Intermediate segment of this escape sequence.
4E N Basic Cyrillic SBCS
51 Q Extended Cyrillic SBCS
53 S Basic Greek (ISO 5428) SBCS

The EACC is the only multibyte encoding of MARC-8, it encodes each CJK character in three ASCII bytes.

For example, to encode the U+4EBA CJK character (人) you will need the following bytes 

 \x1B\x24\x31\x21\x30\x64

The \x1B\x24\x31 switches to EACC/CJK, and the \x21\x30\x64 corresponds to the U+4EBA.

Custom set extension

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In addition to the ISO-2022 character sets, the following custom sets are available too. The byte designation follows the escape byte (hexadecimal 1B). There is no intermediate byte.

Final Bytes[2]
Bytes Characters Name Type Comment
62 b Subscript set SBCS
67 g Greek Symbol set SBCS The alpha, beta, gamma characters normally do not round trip map to Unicode.
70 p Superscript set SBCS
73 s Basic Latin (ASCII) SBCS

C0 control codes

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MARC 21 uses GS (0x1D) as a record terminator, RS (0x1E) as a field terminator and US (0x1F) as a subfield delimiter.[3]

C1 control codes

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The following alternative C1 control code set is defined for bibliographic applications such as library systems. It is mostly concerned with string collation, and with markup of bibliographic fields. Slightly different variants are defined in the German standard DIN 31626[4] (published in 1978 and since withdrawn)[5] and the ISO standard ISO 6630,[6][7] the latter of which has also been adopted in Germany as DIN ISO 6630.[8] Where these differ is noted in the table below where applicable. MARC-8 uses the coding of NSB and NSE from this set, and adds some additional format effectors in locations not used by the ISO version; however, MARC 21 uses this control set only in MARC-8 records, not in Unicode-format records.[3]

If using the ISO/IEC 2022 extension mechanism, the DIN 31626 set is designated as the active C1 control character set with the sequence 0x1B 0x22 0x45 (ESC " E),[4] and the ISO 6630 / DIN ISO 6630 set is designated with the sequence 0x1B 0x22 0x42 (ESC " B).[6] The 1985 expansion of the ISO 6630 set can also be explicitly specified by using the sequence 0x1B 0x26 0x40 0x1B 0x22 0x42 (ESC & @ ESC " B).[7]

Esc+ Dec Hex Acro Name Description[4][6][7]
G 135 87 CUS Close-Up for Sorting (DIN 31626, ISO 6630) Declares that two successive character sequences separated by a space or separator should be treated as one word for collation purposes.
H 136 88 NSB Non-Sorting Characters Begin (DIN 31626, ISO 6630, MARC 21) Marks the start of a sequence of characters to be ignored for collation purposes. MARC 21 uses this character in MARC-8 records, but uses 0x98 (SOS) in Unicode records for the same purpose.[3][9]
I 137 89 NSE Non-Sorting Characters End (DIN 31626, ISO 6630, MARC 21) Marks the end of a sequence of characters to be ignored for collation purposes. MARC 21 uses this character in MARC-8 records, but uses 0x9C (ST) in Unicode records for the same purpose.[3][9]
J 138 8A FIL Filler Character (DIN 31626) Substitutes for a mandatory alphanumeric character in a field.
K 139 8B TCI Tag in Context Indicator (DIN 31626) Within a bibliographic field, used to refer to data in another bibliographic field by its tag number.
PLD Partial Line Down (ISO 6630) Not in the original edition of ISO 6630.[6] In the 1985 edition of ISO 6630,[7] used for Partial Line Down (see PLD).
L 140 8C ICI Identification Number in Context Indicator (DIN 31626) Within a bibliographic field, used to refer to data in another bibliographic record by its ID number.
PLU Partial Line Up (ISO 6630) Not in original edition of ISO 6630.[6] In the 1985 edition of ISO 6630,[7] used for Partial Line Up (see PLU).
M 141 8D OSC[a] Optional Syllabification[b] Control (DIN 31626) Marks a syllable boundary in a long word. See also soft hyphen.
ZWJ Joiner (MARC 21) In MARC-8, used for the Zero-Width Joiner, while U+200D is used in Unicode-format MARC records.[3][9]
N 142 8E SS2 Single-Shift 2 (DIN 31626) Non-locking shift code, see SS2.
ZWNJ Non-Joiner (MARC 21) In MARC-8, used for the Zero-Width Non-Joiner, while U+200C is used in Unicode-format MARC records.[3][9]
O 143 8F SS3 Single-Shift 3 (DIN 31626) Non-locking shift code, see SS3.
P 144 90 - (reserved)
Q 145 91 EAB Embedded Annotation Beginning (DIN 31626, ISO 6630) Marks the start of a variable-length annotation which is embedded within a bibliographic field, as opposed to separated using content designation.
R 146 92 EAE Embedded Annotation End (DIN 31626, ISO 6630) Marks the end of a variable-length embedded annotation.
S 147 93 ISB Item Specification Beginning (DIN 31626) Marks the start of a string of specific information of some description, other than a keyword or a permutation string.
T 148 94 ISE Item Specification End (DIN 31626) Marks the end of a string of specific information.
U 149 95 SIB Sorting Interpolation Beginning (ISO 6630) Marks the beginning of a sequence of characters used for collation purposes only.
V 150 96 SIE Sorting Interpolation End (ISO 6630) Marks the end of a sequence of characters used for collation purposes only.
W 151 97 SSB Secondary Sorting Value Beginning (ISO 6630) Marks the start of a string with subordinate collation value.
X 152 98 SSE Secondary Sorting Value End (ISO 6630) Marks the end of a string with subordinate collation value.
Y 153 99 INC Indicator for Non-Standard Character (DIN 31626) Identifies a following non-standard character.
Z 154 9A - (reserved)
[ 155 9B - (reserved)
\ 156 9C KWB Keyword Beginning (DIN 31626, ISO 6630) Marks the start of a keyword within a bibliographic field.
] 157 9D KWE Keyword End (DIN 31626, ISO 6630) Marks the end of a keyword within a bibliographic field.
^ 158 9E PSB Permutation String Beginning (DIN 31626, ISO 6630) Marks the start of a string which is to be permuted to the front of the element when references or indices are generated. Terminated by PSE or by the end of the element.
_ 159 9F PSE Permutation String End (DIN 31626, ISO 6630) Marks the end of a string which is to be permuted to the front of the element.

Notes

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  1. ^ Not the same as the Operating System Command (OSC) in the ISO/IEC 6429 C1 code set.
  2. ^ Spelled "Syllabication [sic]" in the ISO-IR-040 document, along with "syllable" being spelled "syllabe [sic]" in the description. These are presumably typographical errors.

References

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  1. ^ "Character Sets: Introduction: MARC 21 Specifications for Record Structure, Character Sets, and Exchange Media (Library of Congress)". Library of Congress.
  2. ^ a b c "Character Sets: MARC-8 Encoding Environment: MARC 21 Specifications for Record Structure, Character Sets, and Exchange Media (Library of Congress)". Library of Congress.
  3. ^ a b c d e f "Control function codes". MARC 21 Specifications for Record Structure, Character Sets, and Exchange Media. Library of Congress. 2007-12-04.
  4. ^ a b c DIN (1979-07-15). Additional Control Codes for Bibliographic Use according to German Standard DIN 31626 (PDF). ITSCJ/IPSJ. ISO-IR-40.
  5. ^ "Information processing; bibliographic control characters". Beuth: publishing DIN. DIN 31626:1978-12.
  6. ^ a b c d e ISO/TC 46 (1983-06-01). Additional Control Codes for Bibliographic Use according to International Standard ISO 6630 (PDF). ITSCJ/IPSJ. ISO-IR-67.{{citation}}: CS1 maint: numeric names: authors list (link)
  7. ^ a b c d e ISO/TC 46 (1986-02-01). Additional Control Codes for Bibliographic Use according to International Standard ISO 6630 (PDF). ITSCJ/IPSJ. ISO-IR-124.{{citation}}: CS1 maint: numeric names: authors list (link)
  8. ^ "DIN ISO 6630 December 1997". AFNOR Editions Online Store.
  9. ^ a b c d "Code Table Extended Latin (ANSEL)". MARC 21 Specifications for Record Structure, Character Sets, and Exchange Media. Library of Congress. 2007-12-05.
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