O'pain Software Foundation: (2) Why is it better than AT&T?

[Richard A. O'Keefe]

In article <14807 at tut.cis.ohio-state.edu>, karl at triceratops.cis.ohio-state.edu (Karl Kleinpaste) writes:
> Witness IBM's AIX' compatibility with SysVRel[?1?2?] (exactly which is
> unclear to me), ...

This has been mentioned before, but remains a puzzle to me.
We have BSD boxes, SysV boxes, and a couple of RTs, and porting our
stuff to AIX was not a matter of saying make -DSYS5 nor even of mixing
and matching BSD bits and SysV bits, but in several cases of finding
third solutions.  I only read about half of the RT manuals, but for
what it's worth I don't remember seeing any claim of SysV conformance.