Unusual (?) problem with cd in ksh

[David B. Lewis]

The command 
	``
kills ksh when run at the command line or in a shell script.
csh and sh handle it fine.
	`echo pwd` 
and non-null arguments are handled fine.
I noticed this in a script which was in fact executing 
	cd ``

Is a null `` undefined? 
What can be expected of this construct across shells?

(I checked "Unix Shell Programming" by Kochan and Woods without
seeing anything relevent to the exceptional case.)
-- 
David B. Lewis david at ics.com ics!david at buita.bu.edu david%ics.UUCP at buita.bu.edu

"An organization designing a system will produce a copy of its own
communication structure." - Melvin Conway