[TUHS] non-blocking IO

[arnold at skeeve.com]

Paul Winalski <paul.winalski at gmail.com> wrote:

> So I'm curious as to what the rationale was for Unix to have been
> designed with basic I/O being blocking rather than asynchronous.

I don't doubt that it was "simplify, simplify, simplify". Async I/O
is much messier than Unix's read/write model. The Unix model was
simpler to design, simpler to code, simpler to get right, and undoubtedly
took much less OS code than an async model would have; on the PDP-11
that would have mattered.

Also, the early Unixs were on smaller -11s, not the /45 or /70 with
split I&D space and the ability to address lost more RAM.

My guess, anyway. :-)

Arnold