On the documentation page for the tcsh complete command, it lists the symbols [‸D] and [‸C] several times. I haven't found anything from Google. Context suggests that they could be single or double tab, but I can find no reference to support this and wanted to make sure it wasn't something more esoteric.
Any ideas what these are meant to represent?
> complete ftp 'p/1/$hostnames/'
> set hostnames = (rtfm.mit.edu tesla.ee.cornell.edu)
> ftp [‸D]
rtfm.mit.edu tesla.ee.cornell.edu
> ftp [‸C]
> set hostnames = (rtfm.mit.edu tesla.ee.cornell.edu uunet.uu.net)
> ftp [‸D]
rtfm.mit.edu tesla.ee.cornell.edu uunet.uu.net
It's a somewhat unusual way to write ^D, which is Control+D.
This is the "traditional" mapping to trigger completion, although Tab is more commonly used these days. Back in the day not all keyboards had a dedicated Tab key (the ADM-3A, on which csh was originally developed, didn't) and you would insert tabs with ^I, there is no real reason to prefer that over ^D in absence of a dedicated key.