[TUHS] Re: After 50 years, what has the Impact of Unix been?

[Douglas McIlroy <douglas.mcilroy@dartmouth.edu>]

> Pipes were invented at least three times

I would add a 4th: POGOL--a remarkable data-processing language from
NSA, described by Gloria Lambert at the first POPL conference, 1973. A
POGOL program is made of processes that read and write notional files.
The compiler considers all the processes together and optimizes files
out of existence wherever it sees that written data can be read
immediately. Otherwise a buffering file is instantiated. Unlike Unix
pipes, though, a pair of communicating processes must share common
knowledge about the connection--the file name.

A ready-made theory of pipe networks was published essentially
simultaneously with the advent of DTSS communication files:
R.M. Karp, R.E. Miller, and S. Winograd. The organization of
computations for uniform recurrence equations. Journal of the ACM,
14(3):563-590, July 1967.

Completely unsuspecting processes could have been connected by a pair
of DTSS communication files controlled by a master relay process. As
far as I know this was never done, although such a mechanism was used
for the DTSS chat facility.

For the special case of clocked sample-data networks, BLODI (block
diagram compiler) by Lochbaum, Kelly and Vyssotsky was way ahead
(1960) of all the pipe-based formalisms.

Doug