unremovable files?

[Robert Perlberg]

<>

I have on several occasions run into the problem of having a
program create an unremovable file.  If I try:

rm a.out

rm will respond:

a.out: not removed.

(I checked the permissions on the file and the directory - I
should be able to remove it.)
This did not even work when root tried to remove it.  /etc/unlink
fairs no better than rm.  It can be moved:

mv a.out duh

but not removed:

rm duh
duh: not removed

I am able to remove such files by the following method:

mkdir tempdir
mv a.out tempdir
rm -r tempdir

Does anyone know what causes a file like this to be created and
why the system behaves as it does when I try to remove it?
I am running UNIX System III.  I checked the directory with "od
-c" and the link entry has no strange characters in it.

Robert Perlberg
Resource Dynamics Inc.
New York
philabs!rdin!rdin2!perl