On 7/15/2011 1:31 PM, Julian Bradfield wrote:
On 2011-07-15, Leo Broukhis<[email protected]> wrote:
On Fri, Jul 15, 2011 at 12:04 PM, John W Kennedy<[email protected]> wrote:
Those of us old enough to recall IBM's old 6-bit BCDIC code (a retronym -- it was known
as "BCD" in its own day) will remember the overstricken b/ character used to
represent the Substitute Blank character, the overstricken =| character for Record Mark,
and others. (Annoyingly enough, these and some other BCDIC graphics are not covered by
Unicode, which must be a problem for historians.)
There's U+2422 BLANK SYMBOL ␢ and U+241E SYMBOL FOR RECORD SEPARATOR ␞
Are they not enough?
And of course there are other ways: if the Record Mark John is
referring to is the same as the Group Mark in the table I find, it's
It isn't.
actually ≡⃒ , not =⃒ (these two using U+20D2 COMBINING LONG VERTICAL
LINE OVERLAY); the latter could also be represnted as ǂ, the palatal
click).
The record mark (IBM GCGID SS950000) consists of two horizontal lines
crossed
by one vertical line.
The segment mark (IBM GCGID SS960000) consists of three vertical lines
crossed
by one horizontal line.
The group mark (IBM GCGID SS970000) consists of three horizontal lines
crossed
by one vertical line.
Those particular symbols weren't encoded early on in the Unicode Standard,
because nobody had asked that they be encoded.
I suspect that back in 1989, they were considered just vendor specific
glyphs which could be used to display whichever control function was being
used in a particular tape format for tape segmentation of records.
[Incidentally, the BCDIC overstrike hack is revealed for the hack that
is was,
by the fact that it worked for the record mark, but not for the segment mark
or group mark, because the pieces weren't available for overstriking.]
The record mark could currently be considered to be represented in
Unicode by the
math symbol U+29E7 THERMODYNAMIC, which was added to the repertoire
as of Unicode 3.2, when large numbers of such math symbols were added.
(And I wouldn't recommend using the palatal click letter for the record
mark.).
The other two could be proposed as unitary symbols, if anybody really
needs to
represent them. They are commensurate with a large number of similar symbols
consisting of various numbers of horizontal lines crossed by various numbers
of vertical lines. See, e.g., 29FA, 29FB, 2A68, 2A69, 2AF2, 2AF5.
--Ken
