T.51 / ISO/IEC 6937:2001, Information technology — Coded graphic character set for text communication — Latin alphabet, is a multibyte extension of ASCII, or more precisely ISO/IEC 646-IRV.
[1] 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.
ISO/IEC 6937's architects were Hugh McGregor Ross, Peter Fenwick, Bernard Marti and Loek Zeckendorf.
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).
[2] The supplementary set (second half) contains a selection of spacing and non-spacing graphic characters, additional symbols and some locations reserved for future standardisation.
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.
In total 13 diacritical marks can be followed by the selected characters from the primary set: The reference to combining characters in the U+0300—U+036F range for the codes in the range 0xC1—0xCF below is subject to the caveats mentioned above; they cannot simply be mapped to the codepoints listed.
[10] The supplementary set for Data Syntax 3 adds non-spacing marks for a "vector overbar" and solidus and several semigraphic characters.