Re: Ada Run-time for embedded systems

[eachus@spectre.mitre.org (Robert I. Eachus)]

In article <3h2rg8INNhhp@RA.DEPT.CS.YALE.EDU> griest-tom@cs.yale.edu (Tom Griest) writes:

   (I said:) 

  >>   Get real.  For example, both the J-STARS and AWACS aircraft have
  >>workstations as part of the "embedded" radar systems in aircraft.

  > This statement is not completely accurate.  I cannot speak for AWACS,
  > but I do know something about JSTARS.  JSTARS has a "Radar Subsystem".
  > It is separate and distinct from the Operations and Control (O&C)
  > Subsystem which contains the workstations.  There are no workstations
  > in the Radar Subsystem.

    They are an embedded part of the radar system, but not the radar
subsystem.  Fine, so much for hairsplitting.

  > Clearly there is no "law" that states that an embedded system cannot
  > have a display, or even a workstation interface.  The evolution of
  > the technology is such that it is now becoming common practice to
  > "bolt on" front-end workstations on many systems.  The question is:
  > "should these be considered part of the embedded system, or just a
  > computer that communicates with an embedded system?"  The traditional
  > idea of an embedded computer is one in which the computer is dedicated
  > to IMPLEMENTING the functions of some non-data processing system.

    The dividing line IS clear, but not from the outside.  If the
characteristics of the workstation affect the SYSTEM design, and
analysis of the system behavior include the behavior of the
workstation, then the workstation is a part of the system.  If any
workstation acceptable to its user will do, then it is not part of the
system.  I've worked on both types.

  > There probably is no "clean" definition of what an embedded computer
  > is.  Maybe the technology has made the term obsolete.  When your
  > TV's set-top box will be able to plot your stock investments as well
  > as change the channel from a remote "clicker" command, will
  > it be an embedded computer or a general processor?

    A computer can be both an embedded computer and a general purpose
processor.  In many embedded systems the "spare" capacity of a
real-time embedded computer is made available at lower priority for
miscellaneous tasks.

 > Maybe we can expand the definition of "embedded" to all computers
 > and then using the rationale that Ada was designed for "embedded"
 > computers, we can expand its market to all computers!  :-)

   Not quite, but more and more general purpose computer systems are
really embedded computers in disguise.  For example, many workstations
are also an integral part of a corporate network.  (And many aren't.
If the network goes down or is seriously impaired if a particular
computer malfunctions, then that computer is an embedded part of the
network.)

--

					Robert I. Eachus

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