larry@VLSI.JPL.NASA.GOV (04/18/89)
>And...wasn't Ada supposed to run on embedded systems where all tasks >are lightweight, and there is no notion of ...? No, that's propaganda or ignorance. Ada is not a special-purpose language designed for real-time processing. It's an excellent general-purpose programming language with some rudimentary real-time capability. See the two special editions of Ada Letters on the Int'l Workshops on Real-Time Ada Issues for more discussion. What the designers of Ada did was more far-sighted. They designed a language that is not only general-purpose but extensible, via its library and typing mechanisms. Thus it can contain spaceships and invoices as first-class objects that can be used as naturally as numbers and character arrays. (Though this capability requires some tweaking, as the recent discussions of overloading assignment shows.) Anticipating much wider use of distributed and multi-processor computing systems, they included the rudiments of concurrent programming based on communicating sequential processes, rather than semaphores or monitors or such relatively low-level mechanisms which depend upon uni-processor architectures. Larry @ VLSI.JPL.NASA.GOV
griest@AJPO.SEI.CMU.EDU (04/21/89)
Initial Posting (author believed to be pcb@aber-cs.UCP): >>And...wasn't Ada supposed to run on embedded systems where all tasks >>are lightweight, and there is no notion of ...? Response in article 1774 by Larry @ VLSI.JPL.NASA.GOV: >No, that's propaganda or ignorance. Ada is not a special-purpose language >designed for real-time processing. It's an excellent general-purpose >programming language with some rudimentary real-time capability. See the >two special editions of Ada Letters on the Int'l Workshops on Real-Time Ada >Issues for more discussion. I am always amazed by the different ways in which people perceive the same information. I had been under the impression that Ada WAS designed specifically for real-time embedded applications. Maybe it was just a spoof to get in the door, and then take over all application areas! I can remember briefings by Larry Druffel, then director of the AJPO, stating that Ada was designed for real-time applications, but that it may be suitable for other applications as well. I can even remember conversations that Text_IO not be part of the language. Funny that the first sentence of the RM (foreword) refers to "real-time systems". The second and third sentences refer to the requirements effort and specifically to the STEELMAN requirements. And the first sentence of the STEELMAN document states: "The Department of Defense Common High Order Language program was established in 1975 with the goal of establishing a single high order computer programming language appropriate for DoD EMBEDDED COMPUTER SYSTEMS". [emphasis added] I'm curious how one interprets this to imply Ada was NOT designed for real-time processing. However, I can understand a debate as to whether or not it met the goal of supporting real-time embedded applications. Furthermore, I see no indication that the workshop documents referred to above imply anything contrary to this. In fact the preface to the first document states in reference to Ada's use for real time applications: "Ada was designed for embedded systems and so it seems to be very important that issues which are or appear to be problems get analyzed and solved as soon as possible rather than hidden under the carpet." Your implication that Ada was not designed for real-time applications may be harmful if it causes real-time programmers to give up hope for a decent high level language to use. I believe Ada is suitable for real- time, but is certainly not perfect. Hopefully, these imperfections can be addressed in Ada9X. griest@ajpo.sei.cmu.edu