On 2021-11-23 18:59, Koning, Paul wrote:
On Nov 23, 2021, at 12:53 PM, Valery Ushakov <uwe%stderr.spb.ru@localhost> wrote: On Tue, Nov 23, 2021 at 09:22:43 -0500, Greg Troxel wrote:I think (memory is getting fuzzy) the problem is that the old terminals had a delete key, in the upper right, that users use to remove the previous character, and a BS key, upper left, that was actually a carriage control character.[... snip ...]I see the same kbs=^H on vt52.vt52 is different.I spent a lot of time on VT52, VT100, and VT2xx terminals.
Me too. :-)
All DEC terminals have a "delete" or "rub out" key, which transmits 0177. VT52 and VT100 also have a backspace key, which transmits 010. VT2xx (LK201 keyboard) do not have that key. Or rather, they do have a top row function key that is sometimes labeled BS but it sends an escape sequence, and is not taken seriously by most DEC programmers.
It's a bit more convoluted than that. If you set a VT200 in VT100-mode, those three keys on the top row will in fact actually send LF, BS and ESC. Because if you wanted more VT100 compatibility, the VT100 had those keys, so the VT200 also had to have them if in VT100 mode.
But yes, if you are in VT200 mode, they will in fact send various escape sequences.
Not that it's really relevant here. The key to correct typing errors send a DEL, which is what this is about.
DEC software convention always was that the delete/rubout key is how you erase the previous character. Backspace was never used for that, and there wasn't any obvious reason to have it on the keyboard. It is, of course, an output formatting character.
Some DEC software used BS, which is why the VT200 in VT100 mode still had it. One of the more known pieces is FMS, which uses BS to step to the previous field, and TAB to step to the next field (there was no possibility of doing shift-TAB back then, which is popular nowadays for that same function).
Johnny
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