From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on ip-172-31-74-118.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-0.5 required=3.0 tests=BAYES_05 autolearn=ham autolearn_force=no version=3.4.5-pre1 Date: 13 Aug 93 16:06:16 GMT From: fsi-ssd!mikeb@uunet.uu.net (Mike Bates) Subject: Re: Language runtime requirements (was Re: DoD Message-ID: List-Id: VAXELN, DEC's "real-time" OS for VAXen, does a nice job of mapping Ada tasks to the OS; perhaps it's more accurate to say that the OS's structure coincides neatly with Ada's requirements. An Ada program corresponds to a VAXELN job. Tasks map to processes within the job; the main task corresponds to the master process. Scheduling is preemptive, based on job priority, then on priority of processes within the active job. VAXELN Ada has a very useful, "thick" binding for system calls -- I imagine it helps that VAXELN is written in a variant of Pascal. The X and Motif bindings were fairly easy to work with as well. (X and Motif themselves weren't so easy...) We had a few problems with the environment -- device drivers were written for transaction-processing "real-time," not for hard real-time. With the Pascal source for their drivers and some assistance from DEC's customer support, we were able to write the drivers we needed in Ada. The other big problem is that VAXELN's user community is relatively small; we uncovered several previously undiscovered bugs in the Motif library and in the user shell. It's a strange feeling when the customer support engineer says, "We've never known anyone to try that before." -- ------------------------------------------------------------------------------ Mike Bates FlightSafety International, Simulation Systems Div. Principal Engineer 2700 North Hemlock Circle Computer Systems Group Broken Arrow, Oklahoma 74012 mikeb@ssd.fsi.com 918-251-0500 ext. 581