There's an equivalent 6502 routine in Acorn's MOS series, as used in the BBC Micro and derivatives, which had similar text editing functionality. The code from

There's an equivalent 6502 routine in Acorn's MOS series, as used in the BBC Micro and derivatives, which had similar text editing functionality. The code from the BBC Micro version of the OS can be seen here: https://tobylobster.github.io/mos/mos/S-s9.html#SP1 https://tobylobster.github.io/mos/mos/S-s9.html#SP1