#: 7250 S3/Languages
    08-Oct-90  13:11:31
Sb: #7224-#real time languages
Fm: Pete Lyall 76703,4230
To: Bob van der Poel 76510,2203 (X)

Multiple definitions of real-time, I'm afraid.

When I was working weapons systems, real time meant that each submodule had a
time budget, and overall system cycle time was crucial (for things like
launcher order extrapolation, future target position estimation, and so on). If
time overran it's set limit, a note was made and a time loan was established.
This was effectively taken from segments that didn't use all of their allocated
time. If a consistent offense was noted, that module was flagged and faulted
out to the executive.

Other people consider real time environments those that allow for dynamic
inputs, and simultaneously produce resultant output. A pitch shifter (in a
recording studio) is a good example.. a sound goes in, the processor performs
transforms on it, and that same sound is emitted from the outputs (in its
shifted form) almost at the same moment.

Other folks take real time to mean "not batch" (or deferred) processing.

Unfortunately, people think that "real time" is a sexy term, and will misuse it
to make something sound slick. Bet that this is the most common case. I, for
one, don't consider OS9 to be real time. It doesn't have finite periods during
which it must accomplish things, nor does it have the mechanisms to enforce
that kind of operation with its applications.

Back to C, ADA, and multiple concurrent operation. Using C under OS9/Unix, the
OPERATING system provides the facilities. Under ADA, tasking, rendevous, and
the likes are features of the language. I think that's where the distinction
lies.

Pete

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