20 Sep
2015
20 Sep
'15
6:38 a.m.
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