Editing Shift Out and Shift In characters

{{Short description|ASCII control characters}}
[[File:Shift In and Shift out on Linux.png|thumb|right|320px|Shift In and Shift Out used in a Linux terminal to access a variant [[DEC Special Graphics]] set]]
'''Shift Out''' (SO) and '''Shift In''' (SI) are [[ASCII]] [[control character]]s 14 and 15, respectively (0x0E and 0x0F).<ref>{{cite web |title=The Linux Programmer's Manual |url=http://man7.org/linux/man-pages/man7/ascii.7.html |access-date=2012-11-16}}</ref> These are sometimes also called "Control-N" and "Control-O".

The original purpose of these characters was to provide a way to shift a coloured ribbon, split longitudinally usually with red and black, up and down to the other colour in an [[electro-mechanical]] [[typewriter]] or [[teleprinter]], such as the [[Teletype Corporation|Teletype]] Model 38, to automate the same function of manual typewriters. Black was the conventional ambient default colour and so was shifted "in" or "out" with the other colour on the ribbon.

Later advancements in technology instigated use of this function for switching to a different [[font]] or [[character set]] and back. This was used, for instance, in the [[Russian language|Russian]] character set known as [[KOI7|KOI7-switched]], where SO starts printing [[Russian alphabet|Russian letters]], and SI starts printing [[Latin alphabet|Latin letters]] again. Similarly, they are used for switching between [[Katakana]] and Roman letters in the 7-bit version of the Japanese [[JIS X 0201]].<ref>{{cite iso-ir |sponsor=Japanese Industrial Standards Committee |sponsor-link=Japanese Industrial Standards |date=1975-12-01 |title=The Japanese Katakana graphic set of characters |number=13}}</ref><ref>{{cite iso-ir |sponsor=Japanese Industrial Standards Committee |sponsor-link=Japanese Industrial Standards |date=1975-12-01 |title=The Japanese Roman graphic set of characters |number=14}}</ref>

SO/SI control characters also are used to display [[VT100]] [[Box-drawing characters|pseudographics]]. Shift In is also used in the 2G variant<ref>{{citation |mode=cs1 |last=Kawasaki |first=Yusuke |date=2010|title=Emoji encodings and cross-mapping tables in pure Perl |url=https://github.com/kawanet/Encode-JP-Emoji}}</ref> of [[SoftBank Mobile]]'s encoding for [[emoji]].

The [[ISO/IEC 2022]] standard ([[Ecma International|ECMA]]-35, [[Japanese Industrial Standards|JIS]] X 0202) standardises the generalized usage of SO and SI for switching between pre-designated character sets invoked over the 0x20–0x7F byte range. It refers to them respectively as '''Locking Shift One''' (LS1) and '''Locking Shift Zero''' (LS0) in an 8-bit environment, or as SO and SI in a 7-bit environment.<ref>{{cite book |author=ECMA |author-link=Ecma International |date=1994 |title=Character Code Structure and Extension Techniques |edition=6th |section=7.3: Invocation of character-set code elements |type=ECMA Standard |id=ECMA-35 |page=14 |url=https://www.ecma-international.org/wp-content/uploads/ECMA-35_6th_edition_december_1994.pdf}}</ref> In ISO-2022-compliant code sets where the 0x0E and 0x0F characters are used for the purpose of emphasis (such as an italic or red font) rather than a change of character set, they are referred to respectively as '''Upper Rail''' (UR) and '''Lower Rail''' (LR), rather than SO and SI.<ref>{{cite iso-ir |sponsor=Sveriges Standardiseringskommission |date=1975-12-01 |title=NATS Control set for newspaper text transmission |number=7}}</ref>

== See also ==
* [[C0 and C1 control codes]]

== References ==
{{Reflist}}

[[Category:Control characters]]