RE: [OT] What is DEL for?

From: Marco Cimarosti (
Date: Thu Feb 22 2001 - 05:29:15 EST

Frank da Cruz wrote:
> Yes, DEL has many, many uses in the terminal-to-host
> direction, as do most other control characters.
> I probably use DEL about 1000 times a day.

That's what I suspected.

> You can never know what all its uses are. If anybody hopes
> to be able to recycle or abolish it, that would be a bad
> idea. ASCII (ISO 646 IRV) must remain stable and
> inviolable for all time.

According to my Italian-English dictionary, the idiom to express my
situation is "to be caught red-handed".

> DEL does indeed have a use in plain text files that are encoded with
> Shift-In / Shift-Out to switch between left and right halves of (say)
> ISO 8859-1 without having to actually put 8-bit characters in the
> file.

This sounds quite double-byte Greek to me but, if my understanding is
correct, it could be an interesting precedent.

This is what I think I understood:

- Same 8-bit character sets (e.g. Latin-1) may be encoded in 7-bit bytes.

- The same values 0x20..0x7F are used both to represent characters
0x20..0x7F themselves (the "left half", I guess) and characters 0xA0..0xFF
(the "right half", I guess).

- The Shift-In and Shift-Out control characters (0x0F and 0x0E) are inserted
in the text to signal whether or not, from that point onwards, 0x80 has to
be added to each byte's value.

- In this scheme, DEL (0x7F) is used to represent both character 0x7F itself

If you ACK my understanding, the question is: how do these 0x7F bytes
(representing 0xFF characters) interact with terminals/host communication?

> Ditto for "higher" levels of ISO-2022 character-set invocation (LS3, etc).

Could I find ISO-2022 on-line (or an unofficial explanation of it)?

Thanks. Ciao.
_ Marco

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