For the most part, we illustrate
under BSD UNIX
and its variants (such as SunOS 4.x). Where AT&T System V (SysV) differs
(such as Sun's Solaris 2.x), we illustrate those differences.
Our primary focus throughout this book is on version 8.8
For completeness, and where necessary, we also discuss V8.7 and earlier
(such as BSD's version 5,
IDA, early Sun, Ultrix, and NeXT).
 The versions jump from 5 to 8 because the managers of the BSD 4.4 UNIX
distribution wanted all software to be released as version 8. Prior to that
decision, the new BSD
was designated Version 6. V6
survived only the alpha and beta releases before being bumped to V8.