Subject: Dating the addition of pipes in UNIX

From: Warren Toomey <wkt>
Date: Tue, 19 Jan 1999 10:53:28 +1100 (EST)

Dennis,
	Let me know if I'm bothering you with all of this email. I'm sure
that you've got other, better things to do than answer questions about old
stuff.

I'd love to know if anybody can remember the date that Ken hacked pipes
into the Unix kernel. The nsys kernel is dated Jan 22 1973, and Peter
Salus' book say that the 3rd Edition manuals came out in February 1973.

Now, nsys doesn't have pipes, but has a system call reserved for pipes:

	   0, &nosys,                      /* 42 = pipe */

If the 3rd Edition manuals did come out in February, and nsys didn't have
pipes in late January, then they must have been added during that interval.

Also, was there a period when the kernel was being developed both in
assembly language and in a HLL (pre-C)? You've said that ``Ken started
trying [to rewrite the kernel in C] in the summer of 1972 and gave up. ...
Over the year, I added structures ... and so over the next summer, we made
the concerted effort and actually did redo the whole operating system in C.''

If nsys is dated January 1972 (i.e your winter), then either you last
statement isn't quite correct, or nsys was a snapshot of a parallel
development which culminated in a new system by summer 1973.

Thanks again,
	Warren