On 2018-11-01, Tinker <[email protected]> wrote: >> > No idea how ^4 is mapped to ^\, but for some reason it is, >> >> See "Table 3-5 Keys Used to Generate 7-Bit Control Characters" in >> the VT220 Programmer Reference Manual: >> https://vt100.net/docs/vt220-rm/table3-5.html > > Historial reasons, a ha.
And I'll venture a guess why DEC added those combinations: In order to type ^[ ^\ ^] to produce the ESC, FS, GS characters, you need keys for [ \ ]. If you look at non-English keyboard layouts, you'll see that the corresponding keys have been re-purposed for other characters. In the old days of national ASCII variants, even the characters [ \ ] didn't exist in many national encodings. Later, when extended 8-bit character sets were introduced, [ \ ] were only made available in a secondary mapping reachable with an extra modifier key (AltGr or such). And that's the situation right into the present. By contrast, combinations like ^3, ^4, ^5 were readily available on keyboards. https://en.wikipedia.org/wiki/ISO/IEC_646#ISO_646_national_variants -- Christian "naddy" Weisgerber [email protected]
