Unix Systems

Research Unix	The versions of Unix developed at Bell Laboratories
USL/USG	Systems developed by the Unix Support Group and the Unix System Laboratories
Other Early Unixes	Modified versions of early Unix developed outside the Labs
Early BSDs	The 16-bit BSDs from the University of California, written for the PDP-11
32-bit BSDs	The 32-bit BSDs for the VAX and other hardware architectures
Commercial Unixes	Commercial versions of Unix sold by AT&T and other companies
Unix Derivatives	Systems that are derived from Unix but no longer have any Unix source code