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> Del key, which on a scoansi terminal emits ^?

^? = ASCII DEL[elete] = 0x7F. Terminals where the Delete key sends Delete are doing it right.

Why is DEL 0x7F, when other control codes are <0x20? Because the American Standard Code for Information Interchange descended from teletype codes, and teletypes often used paper tape ‘storage’ where a 1 bit was a hole. So teletype codes would normally have a delete function punch all holes, because that would obliterate any other possible character (and typical of punches, advance to the next position, making DEL semantically a forward delete operation).

> on a vtxx terminal the Del key emits a multi byte escape sequence

Only VTxxx where xxx ≥ 200. The VT100 series and earlier had ASCII Delete and Backspace keys, but in the VT2xx era DEC got some funny ideas and provided only a ⌫ key, which left us an enduring mess.



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