[TUHS] Synchronous vs Asynchronous IO in Unix

[Peter Jeremy]

Why were the original read(2) and write(2) system calls written to offer
synchronous I/O only?  It's relatively easy to create synchronous I/O
functions given asynchronous I/O primitives but it's impossible to do the
opposite.

Multics (at least) supported asynchronous I/O so the concept wasn't novel.
And any multi-tasking kernel has to support asynchronous I/O internally so
suitable code exists in the kernel.

-- 
Peter Jeremy
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