Re: CP1252 under Unix

From: Markus Kuhn (
Date: Sat Mar 25 2000 - 13:40:15 EST

Frank da Cruz wrote on 2000-03-25 17:23 UTC:
> Then Markus went on to list the graphics in the 0x80-0x9F range of CP1252.
> Now, I was reading his message in a terminal window (in Windows, by the
> way, not Unix) that conforms to ISO 2022, 4873, and 6429. Here's what
> happened:
> This is C1 control APC (Application Program Command). It makes any ANSI
> X3.64 / ISO-6429 compliant terminal hang forever waiting for the rest of
> the APC sequence, which never comes. Thank goodness for the reset button.

Taking my spare-time character-set fanatic hat off and putting my
day-job computer security hat on for a moment, I'd strongly advise Frank
(and developers of email software that runs in VT100 emulators) to
ensure that only the following C0/C1 characters received from outside
the ivory tower ever be forwarded to the terminal: CR+LF, TAB.
Everything else *must* be substituted for a blinking red question mark,
a fancy 2-digit hex number in rotating rainbow colours, or something
else genuinely harmless, as otherwise hostile (as opposed to ignorant)
sources of information can do bad things to your terminal any time. The
"less" pager under Unix usually does a fine job of that for instance
(and starting with version 346 it even supports UTF-8!).


Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at,  WWW: <>

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