Re: [OT] What is DEL for?

From: Frank da Cruz (
Date: Wed Feb 21 2001 - 13:49:19 EST

> > Which systems interpret 0x7F as "interrupt process"? I know that this would
> > be 0x03 in DOS (^C), and 0x03, 0x04 or 0x1A in Unix (^C, ^D, and ^Z,
> > respectively), but I know nothing about other systems, e.g. Macintosh.
> Very long ago, in the Seventh Edition of Unix, the default interrupt
> character was DEL, because it was (as Uwe writes) available on old
> terminals without the need to hold down any shift key.
> But even then most people changed it to ^C in actual practice.
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.
We all should be familiar with the BS/DEL confusion, but those who aren't
might want to take a look at:

> > 1) What happens if emacs loads Doug Ewell's text file (I.e. a text file
> > containing "ABC<del>DEF") and then saves it? Would the file's content be
> > changed to "ABDEF"?
> No. As part of a text file, DEL has no known significance on any
> system.
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.

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

DEL is used by some (non-ANSI-X3.64) terminals for specific purposes,
and others for padding.

- Frank

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