Shift Out and Shift In characters
Shift Out (SO) and Shift In (SI) are ASCII control characters 14 and 15, respectively (0x0E and 0x0F).[1] 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
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
SO/SI control characters also are used to display
The ISO/IEC 2022 standard (ECMA-35, 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.[5] 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.[6]
See also
References
- ^ "The Linux Programmer's Manual". Retrieved 2012-11-16.
- ISO-IR-13.
- ISO-IR-14.
- ^ Kawasaki, Yusuke (2010). Emoji encodings and cross-mapping tables in pure Perl.
- ^ ECMA (1994). "7.3: Invocation of character-set code elements". Character Code Structure and Extension Techniques (PDF) (ECMA Standard) (6th ed.). p. 14. ECMA-35.
- ISO-IR-7.