8-bit Character Sets - ISO/IEC 4873
This standard specifies a structure for 8-bit codes that builds on the general structure for such codes laid down in ISO/IEC 2022. In particular the content of the GL area of the code table is fully specified and the content of the GR area is restricted to be a character set that makes use of single-byte coding (and so contains at most 96 characters). The fixed content for the GL area is the set registered in the ISO 2375 Register as ISO-IR 6. This set is also the International Reference Version (IRV) of ISO/IEC 646:1991 and is more commonly known as the ASCII character set.
- ISO/IEC 4873:1991
- Information technology - ISO 8-bit code for information interchange -
Structure and rules for implementation (third edition).
The code extension techniques permitted by ISO/IEC 4873 are only a selection
of those specified by ISO/IEC 2022.
ISO/IEC 4873 specifies three levels of implementation:
- Level 1 requires a C0 set in addition to the fixed (ASCII) G0 set and it
permits a C1 set and a G1 set to be present. It does not permit the use of
a G2 or G3 set. The C1 and G1 sets, if present, are invoked in the CR and GR
- Level 2 includes the facilities of level 1 but permits, in addition, a G2
and G3 set that may be invoked by means of the single-shift control functions
SS2 and SS3. The C1 set is required to be present and to contain at least the
SS2 and SS3 control functions at positions 08/14 and 08/15 respectively. A
C1 set containing only these two control functions is registered as ISO-IR
105. The use of locking shifts is not permitted.
- Level 3 includes the facilities of level 2 but permits, in addition, the
use of the locking shifts LS1R, LS2R and LS3R.
The coding of single shifts and locking shifts is given in the section of this
guide on control functions.
A collection of coded graphic character sets suitable for use within the
structure of ISO/IEC 4873 has been standardized in ISO/IEC 10367.
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