Where is CSPECL used?

[Peng Yu]

I don't see where CSPECL is used. Is it used anywhere?

It is defined for ASCII letters of 1 and 127. Why these characters are
different from other control characters?

$ ack CSPECL
syntax.h
56:#define CSPECL               0x0010  /* special character that needs quoting 
*/

lib/sh/shquote.c
337:      /* I should probably use the CSPECL flag for these in
sh_syntaxtab[] */

syntax.c
14:     CSPECL,         /* CTLESC */
140:    CSPECL,         /* CTLNUL */

mksyntax.c
56:     { CSPECL,       "CSPECL" },
230:  addcchar (CTLESC, CSPECL);
231:  addcchar (CTLNUL, CSPECL);

-- 
Regards,
Peng