ISO/IEC 6937

ISO/IEC 6937:2001, Information technology — Coded graphic character set for text communication — Latin alphabet, is a multibyte extension of ASCII, or rather of ISO/IEC 646-IRV. It was developed in common with ITU-T (then CCITT) for telematic services under the name of T.51, and first became an ISO standard in 1983. Certain byte codes are used as lead bytes for letters with diacritics (accents). The value of the lead byte often indicates which diacritic that the letter has, and the follow byte then has the ASCII-value for the letter that the diacritic is on. Only certain combinations of lead byte and follow byte are allowed, and there are some exceptions to the lead byte interpretation for some follow bytes. However, that no combining characters at all are encoded in ISO/IEC 6937. But one can represent some free-standing diacritics, often by letting the follow byte have the code for ASCII space.

ISO/IEC 6937's architects were Hugh McGregor Ross, Peter Fenwick, Bernard Marti and Loek Zeckendorf.

ISO6937/2 defines 327 characters found in modern European languages using the Latin alphabet. Non-Latin European characters, such as Cyrillic and Greek, are not included in the standard. Also, some diacritics used with the Latin alphabet like the Romanian comma are not included, using cedilla instead as no distinction between cedilla and comma below was made at the time.

IANA has registered the charset names ISO_6937-2-25 and ISO_6937-2-add for two (older) versions of this standard (plus control codes). But in practice this character encoding is unused on the Internet.

The ISO/IEC 2022 escape sequence to specify the right-hand side of the ISO/IEC 6937 character set is ESC - R (hex 1B 2D 52).^[1]

Single byte characters

The primary set of ISO6937/2 is based on ISO 646-IRV (characters 0x00..0x7F) before the ISO/IEC 646:1991 revision, that is with character 0x24 still denoted as a "international currency sign" (¤) instead of the dollar sign ($):

	!"#¤%&'()*+,-./0123456789:;<=>?@
	ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`
	abcdefghijklmnopqrstuvwxyz{|}

The supplementary set (characters 0x80..0xFF) contains a selection of spacing and non-spacing graphic characters, additional symbols and some locations reserved for future standardisation.

Two byte characters

The characters, which are not represented in the primary set, are coded on two bytes. The first byte, the "non spacing diacritical mark", is followed by a letter from the base set e.g.:

small e with acute accent (é) = [Acute]+e

In total 13 diacritical marks can be followed by the selected characters from the primary set:

Codepage layout

The reference to combining characters in the U+0300—U+036F range for the codes in the range 0xC1—0xCF below are only indicative of which “accent” is usually intended by that lead byte. ISO/IEC 6937 does not encode any combining characters whatsoever. Instead, there is an explicit list of precomposed characters that are encoded.

A little anomaly is that Latin Small Letter G with Cedilla is coded as if it were with an acute accent, that is, with a 0xC2 lead byte, since due to its descender interfering with a cedilla, the lowercase letter is usually with turned comma above: Ģ ģ.

Unicode distinguishes 0xE2 into uppercase Eth and D with stroke, which usually look different for the lowercase letters (0xF2 and 0xF3).

Legend:

References

Character encodings
Character sets
Early telecommunications	ASCII ISO/IEC 646 ISO/IEC 6937 T.61 BCDIC Baudot code Morse code (Telegraph code Wabun code) Special telegraphy codes: Non-Latin, Chinese, Cyrillic
ISO/IEC 8859	-1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12 -13 -14 -15 -16
Bibliographic use	ANSEL ISO 5426 / 5426-2 / 5427 / 5428 / 6438 / 6861 / 6862 / 10585 / 10586 / 10754 / 11822 MARC-8
National standards	ArmSCII CNS 11643 GOST 10859 GB 18030 HKSCS ISCII JIS X 0201 JIS X 0208 JIS X 0212 JIS X 0213 KOI-7 KPS 9566 KS X 1001 PASCII SI 960 TIS-620 TSCII VISCII YUSCII
EUC	CN JP KR TW
ISO/IEC 2022	CN JP KR CCCII
MacOS code pages ("scripts")	Arabic Mac OS Celtic CentEuro ChineseSimp / EUC-CN ChineseTrad / Big5 Croatian Cyrillic Devanagari Dingbats Farsi Gaelic Greek Gujarati Gurmukhi Hebrew Iceland Japanese / ShiftJIS Korean / EUC-KR Roman Romanian Symbol Thai / TIS-620 Turkish Ukrainian
DOS code pages	100 111 112 113 151 161 162 163 164 165 220 300 301 437 449 620 667 668 708 709 710 711 720 737 770 771 772 773 774 775 776 777 778 790 808 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 872 874 876 877 878 881 882 883 884 885 891 895 897 898 899 900 903 904 906 907 909 910 911 925 926 927 928 929 932 934 936 938 941 942 943 944 946 947 948 949 950/1370 951 966 991 1004 1034 1039 1040 1041 1042 1043 1044 1046 1086 1088 1090 1092 1093 1098 1108 1109 1114 1115 1116 1117 1118 1119 1125 1126 1127 1131 1139 1161 1162 1167 1168 1351 1361 1362 1363 1372 1373 1374 1375 1380 1381 1385 1386 1391 1392 1393 1394 17248 Kamenický Mazovia CWI-2 KOI8 MIK Iran System
IBM AIX code pages	367 371 806 813 819 895 896 901 902 912 913 914 915 916 919 920 921 922 923 952 953 954 955 956 957 958 959 960 961 962 963 964 965 970 971 1006 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1029 1036 1089 1111 1124 1129 1133 1163 1350 1382 1383
IBM Apple MacIntosh Emulations	1275 1280 1281 1282 1283 1284 1285 1286
IBM Adobe Emulations	1038 1276 1277
IBM DEC Emulations	1021 1023 1100 1101 1102 1103 1104 1105 1106 1107 1287 1288
IBM HP Emulations	1050 1051 1052 1053 1054 1055 1056 1057 1058
Windows code pages	874/1162 (TIS-620) 932/943 (Shift JIS) 936/1386 (GBK) 950/1370 (Big5) 949/1363 (EUC-KR) 1169 1174 1200 (UTF-16LE) 1201 (UTF-16BE) 1250 1251 1252 1253 1254 1255 1256 1257 1258 1261 1270 54936 (GB18030)
EBCDIC code pages	1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 29 30 31 32 33 34 35 36 37/1140 38 39 40 251 252 254 256 257 258 259 260 264 273/1141 274 275 276 277/1142 278/1143 279 280/1144 281 282 283 284/1145 285/1146 286 287 288 289 290 293 297/1147 298 310 320 321 322 330 351 352 353 355 357 358 359 360 361 363 382 383 384 385 386 387 388 389 390 391 392 393 394 395 410 420/16804 421 423 424/12712 425 435 500/1148 803 829 833 834 835 836 837 838/1160 839 870/1153 871/1149 875/9067 880 881 882 883 884 885 886 887 888 889 890 892 893 905 918 924 930/1390 931 933/1364 935/1388 937/1371 939/1399 1001 1002 1003 1005 1007 1024 1025/1154 1026/1155 1027 1028 1030 1031 1032 1033 1037 1047 1068 1069 1070 1071 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1087 1091 1097 1110 1112/1156 1113 1122/1157 1123/1158 1130/1164 1132 1136 1137 1150 1151 1152 1159 1165 1166 1278 1303 1364 1376 1377 JEF KEIS
Platform specific	ATASCII Atari ST BICS CDC CPC DEC Radix-50 DMCS/NRCS ELWRO-Junior FIELDATA GEM GEOS GSM 03.38 HP Roman Extension HP Roman-8 HP Roman-9 HP calculators LICS LMBCS NEC APC NeXT PETSCII TI calculators WISCII XCCS ZX80 ZX81 ZX Spectrum
Unicode / ISO/IEC 10646	UTF-1 UTF-7 UTF-8 UTF-16 (UTF-16LE/UTF-16BE) / UCS-2 UTF-32 (UTF-32LE/UTF-32BE) / UCS-4 UTF-EBCDIC GB 18030 BOCU-1 CESU-8 SCSU
Miscellaneous code pages	ABICOMP APL Cork HZ JOHAB TRON UTF-5 UTF-6 WTF-8
Related topics	Control character (C0 C1) CCSID Character encodings in HTML Charset detection Han unification Hardware ISO 6429/IEC 6429/ANSI X3.64 Mojibake