File completion in BSD4.3-derived CSH

[Marcus Leech]

I didn't want to clutter up comp.unix.wizards with this one.

Can someone explain to me the mechanism used by the BSD4.3 CSH
  to implement file completion, given that, as far as I can tell,
  it runs the TTY in COOKED mode?  I have Apollos and HP9000/3xx
  with the BSD4.3 CSH.  Both systems have file completion, but I
  can't figure out HOW the CSH gets to see the ESC char given that
  it runs the TTY in COOKED mode.  Someone care to enlighthen me?
I looked for an "alternate" line-discipline, but CSh uses the default
  regular line-discipline.  On the HP, there's no V7ish "alternate
  line-terminator character" that it could be setting to ESC.  I'm
  quite puzzled.
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Marcus Leech, 4Y11             Bell-Northern Research  |opinions expressed
mleech at bnr.ca                  P.O. Box 3511, Stn. C   |are my own, and not
VE3MDL at VE3JF.ON.CAN.NA         Ottawa, ON, CANADA      |necessarily BNRs