Editing ASCII (section)

===<span class="anchor" id="7-bit"></span>7-bit codes===
{{Main|ISO/IEC 646|ITU T.50}}{{See also|UTF-7}}
From early in its development,<ref>"Specific Criteria", attachment to memo from R. W. Reach, "X3-2 Meeting – September 14 and 15", September 18, 1961</ref> ASCII was intended to be just one of several national variants of an international character code standard.

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International Reference Alphabet (IRA)
International Alphabet No. 5 (IA5) -->
Other international standards bodies have ratified character encodings such as [[ISO 646]] (1967) that are identical or nearly identical to ASCII, with extensions for characters outside the English [[alphabet]] and symbols used outside the United States, such as the symbol for the United Kingdom's [[pound sterling]] (£); e.g. with [[code page 1104]]. Almost every country needed an adapted version of ASCII, since ASCII suited the needs of only the US and a few other countries. For example, Canada had its own version that supported French characters.

Many other countries developed variants of ASCII to include non-English letters (e.g. [[é]], [[ñ]], [[ß]], [[Ł]]), currency symbols (e.g. [[£]], [[¥]]), etc. See also [[YUSCII]] (Yugoslavia).

It would share most characters in common, but assign other locally useful characters to several [[code point]]s reserved for "national use". However, the four years that elapsed between the publication of ASCII-1963 and ISO's first acceptance of an international recommendation during 1967<ref name="Maréchal_1967">{{citation |author-last=Maréchal |author-first=R. |title=ISO/TC 97 – Computers and Information Processing: Acceptance of Draft ISO Recommendation No. 1052 |date=1967-12-22}}</ref> caused ASCII's choices for the national use characters to seem to be ''de facto'' standards for the world, causing confusion and incompatibility once other countries did begin to make their own assignments to these code points.

ISO/IEC 646, like ASCII, is a 7-bit character set. It does not make any additional codes available, so the same code points encoded different characters in different countries. Escape codes were defined to indicate which national variant applied to a piece of text, but they were rarely used, so it was often impossible to know what variant to work with and, therefore, which character a code represented, and in general, text-processing systems could cope with only one variant anyway.

Because the bracket and brace characters of ASCII were assigned to "national use" code points that were used for accented letters in other national variants of ISO/IEC 646, a German, French, or Swedish, etc. programmer using their national variant of ISO/IEC 646, rather than ASCII, had to write, and thus read, something such as

<code>ä aÄiÜ = 'Ön'; ü</code>

instead of

<code>{ a[i] = '\n'; }</code>

[[C trigraph]]s were created to solve this problem for [[ANSI C]], although their late introduction and inconsistent implementation in compilers limited their use. Many programmers kept their computers on ASCII, so plain-text in Swedish, German etc. (for example, in e-mail or [[Usenet]]) contained "{, }" and similar variants in the middle of words, something those programmers got used to. For example, a Swedish programmer mailing another programmer asking if they should go for lunch, could get "N{ jag har sm|rg}sar" as the answer, which should be "Nä jag har smörgåsar" meaning "No I've got sandwiches".

In Japan and Korea, still {{As of|2021|alt=as of the 2020s|post=,|df=US}} a variation of ASCII is used, in which the [[backslash]] (5C hex) is rendered as ¥ (a [[Yen sign]], in Japan) or ₩ (a [[Won sign]], in Korea). This means that, for example, the file path C:\Users\Smith is shown as C:¥Users¥Smith (in Japan) or C:₩Users₩Smith (in Korea).

In Europe, [[teletext character set]]s, which are variants of ASCII, are used for broadcast TV subtitles, defined by [[World System Teletext]] and broadcast using the DVB-TXT standard for embedding teletext into DVB transmissions.<ref>{{Cite web |url=https://dvb.org/?standard=specification-for-conveying-itu-r-system-b-teletext-in-dvb-bitstreams |title=DVB-TXT (Teletext) Specification for conveying ITU-R System B Teletext in DVB bitstreams}}</ref> In the case that the subtitles were initially authored for teletext and converted, the derived subtitle formats are constrained to the same character sets.