^B and ^C in tbl output

[phil%rice at sri-unix.UUCP]

From:  William LeFebvre <phil at rice>

Those control Bs and control Cs are NOT delimeter characters.  But
don't worry, that is what I thought they were, also.  They are field
and padding characters.  After tbl sets up a ton of number registes
that use those characters, it does a ".fc ^B ^C" which sets the field
delimeter to ^B and the padding indicator to ^C.  The "Nroff/Troff
User's Manual" explains fields in section 9.2 (page 18).  I am not
exactly sure how they work, be cause I only discovered their existence
a few days ago.  Here is a section of the manual that describes their
use:

	The field length is the distance on the input line from the
	position where the field begins to the next tab stop.  The
	difference between the total length of all the sub-stings and
	the field length is incorporated as horizontal padding space
	that is divided among the indicated padding places.

Those control characters are not "spurious".  They are used to position
strings inside the table segments.  Take them out and your talbe won't
look very pretty.  As for the me special characters not working inside
a table, I suspect that that is caused by "backslash confusion."
Backslashes don't work the same inside a keep as they do in straight
text.  Try defining a string macro that overstrikes a slash and a
backslash that can be used both inside and outside a keep!  It can be
done, but not obviously.  The bottom line is that those control
characters should not interfere with anything.  I would like to see a
case where they do!

                                William LeFebvre
                                ARPANet and CSNet: phil at rice
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