ECMA-23

ECMA-23 is a standard for a bit-paired keyboard layout
adopted in 1969 and revised in 1975. As a bit-paired layout, shifted keys
correspond to toggling bits in the ASCII keycode.
This is most visible in the digits on the top row, where shifting
 give , and ,
 and are paired.
The ECMA-23 layout has two options, being the same as the ISO 2530 or the ANSI-X4.14 bit-paired layout.
In the UK, ECMA-23 layout keyboards were used on most 8-bit computers such as the
Acorn BBC computers and the earlier Atom and Systems, the Amstrad CPC series, and
(to an extent) the ZX Spectrum. While bit-paired layouts have generally given way
to typewriter layouts it remains as the Japanese keyboard layout.
Technical details.
The most common layouts are: