Re: C1 Control Pictures Proposal

From: Andrew West <>
Date: Thu, 18 Aug 2011 00:38:35 +0100

On 13 August 2011 18:48, Sean Leonard <> wrote:
> The Unicode code points U+0000 through U+00FF share the equivalent values from the ASCII Standard, ISO 646, ISO 6429, and ISO 8859-1. In many contexts, it is desirable to display all of these code points/characters uniquely and unambiguously. C0 Control Pictures are currently encoded in the Unicode Standard at U+2400; that block currently covers the undisplayable code points at U+0000-U+0020 (plus a few extra alternatives/additions). However, the undisplayable characters in U+0080-U+00FF are left out.
> There are several business cases in which C1 Control Pictures are useful:
> 1. Terminal emulators need them for debugging.
> 2. Data analyzers need them so they can have a unique character that when the graphics subsystem/text renderers render each character, is intended for display rather than for control effects.
> 3. Engineers can distinguish when communicating between the data without side-effects (i.e., control characters as pictures), and the data that invokes side-effects (i.e., control characters used as control characters).
> 4. There are use cases for historic or scholarly purposes, to encode and discuss these characters in text, as distinct from invoking their side-effects (and displaying nothing).
> 5. To display all values in U+0000 - U+00FF as distinct _characters_, rather than in hexadecimal representation (which makes deciphering the meaning of the codes for graphic characters in the ASCII (G0) & ISO 8859-1 (G1) range very difficult), in the same width and font as the rest of the graphic characters.
> 6. In support of 1-5, font designers can design fonts that support C1 Control Pictures and that map glyphs to Unicode code points uniformly and interchangeably (two key architectural goals of the Unicode Standard). Without C1 Control Pictures, it is infeasible to provide graphical representations of the C1 Control Characters. This is an asymmetry compared to the C0 Control Pictures block in Unicode, and thus should be remedied.

It would probably be useful to read the WG2 Principles and Procedures document


particularly Annex H "Criteria for encoding symbols", which states that:

"The fact that a symbol merely seems to be useful or potentially
useful is precisely not a reason to code it.
Demonstrated usage, or demonstrated demand, on the other hand, does
constitute a good reason to
encode the symbol." (H10 on p.37)

Unless you can show evidence that C1 control pictures are currently in
use and that there is a clear demand from the user community to
represent them in plain text it is unlikely that your proposal will
get very far.

Received on Wed Aug 17 2011 - 18:43:44 CDT

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