System V Release 4.0 versus BSD

[Guy Harris]

>From the two weeks of classes I took in New Jersy on the new AT&T 
>WGS product line, System VR4 was discussed.  It is a hybrid of System
>V (all of them), Xenix and BSD.  It will be compatable with all of 
>the old system V's, Xenix and BSD, so binary portablily is possible.

Well, err, umm, binary portability is possible within limits, in the
case of BSD. 

Binary portability from BSD to S5R4 might be possible with enough work,
but you won't get it for free.  The 32-bit UIDs and GIDs in S5R4's
BSDish "stat" structure get in the way, for example.  If a vendor is,
for example, offering a BSD-based system and switches to S5R4, they'll
have to do some work to provide binary compatibility.

Lots of programs written for BSD will be portable in *source* form to
S5R4; some more will be portable if the vendor includes the BSD
compatibility package.