Re: Unbuffered keyboard input on VAX ADA?

[kilgallen@eisner.decus.org (Larry Kilgallen, LJK Software)]

In article <EMERY.95Feb3123217@goldfinger.mitre.org>, emery@goldfinger.mitre.org (David Emery) writes:

> This example indicates why, in my opinion, such "thin bindings" are A
> Bad Thing.  

I presume you refer to the fact that there are two status codes to be
checked (actually the TASKING_* bindings cited by one user are not all
that thin, being developed specifically for Ada tasking support).

Regardless of possible rearrangement of the parameters, asynchronous
IO will always require two status checks on VMS (or any other OS, so
far as I can see), one for when the request is queued and one for when
it is completed.  If the request does not get queued, the event which
indicates completion (AST for VMS) will never happen.

Of course an exception could be raised in place of one of the failure
returns if it was extremely unlikely, but that probability cannot
be predicted by the designer of bindings.  While the class problem
which started this presumed there was a single keyboard, in a real
situation there could be a score of keyboards, some potentially in
use by other jobs on the computer system at the time when I/O is
requested.