System N history correction

[Guy Harris]

> It's time to set this long-standing misconception straight:
> System N are *not* derived from V7; they are derived from a late V6.

What do "V6" and "V7" refer to here?  There was only one tape sent out
with the Sixth Edition of the UNIX Programmer's manual, so in that sense
there is no such thing as an "early" or "late" V6.  I consider the main things
that distinguish V6 from V7 to be the file system (and system calls changed
for the new file system) and the Bourne shell; System III had that (heck,
UNIX/TS 1.0 had that).  As such, I consider them derived from a system
between V6 and V7, but closer to V7 than V6.

	Guy Harris
	{seismo,ihnp4,allegra}!rlgvax!guy