In 1975 a standard emerged that allowed switching between different
character sets on the fly. It defined escape sequences that could be
used to indicate what character set to use next. Originally intended
in a limited way to allow switching (and signalling) of different
character sets in a 7-bit environment, it grew into more and is now
used in both 7-bit and 8-bit environments. The current version is
on-line as ECMA-35
a standard of the European Computer Machinery Association.
The standard defines standard escape sequences to allow switching
between sets. Moreover, it provides a register where sets can be
registered and receive a sequence to invoke the set. For the time
being on this site access to these sets (and other standardized
things) is only available through the escape
sequences.