🚀 go-pugleaf

On 25 Dec 92 03:39:18 GMT, kolding@cs.washington.edu (Eric Koldinger) said:

kolding> Last I checked (4 years ago), the AS/400 supported RPG III,
kolding> COBOL (I think), Pascal, PL/I, and they were coming out with a
kolding> C compiler.

Actually it's going to be even more bizarre. IBM have stated that C is
going to become their major app dev language on the AS/400 (and in
general across the whole SAA base, which now includes DCE!), which fact
is quite amazing; as a side note I don't think Pascal is in SAA, so
probably it is not supported on AS/400; and I seem to remember that PL/1
is not available yet, even if it is 'scheduled' as it is in SAA.

kolding> You don't generally use the capabilities at the applications
kolding> level, and the languages provide no real ability to manipulate
kolding> capabilities

Actually I think that C on the AS/400 just runs in a 16MB memory object
like most other tradictional languages. In much the same way it was
implemented on the Burroughs descriptor machines.

kolding> (I've often wondered exactly what C ended up looking like on
kolding> that machine, as pointers and ints are definitely not the same,
kolding> and casting an int to a pointer makes no sense).

The AS/400 is Not a VAX - I can see a nice Spencer article on that being
written up when we will all have AS/400s on our desks :-).

kolding> There's a fundamental difference between hardware and software
kolding> capabilities.  Software capabilities can be forged, however
kolding> improbable.  For example, Amoeba capabilities are just long
kolding> integers (32, 64 bits?).  You can forge one, but I wouldn't bet
kolding> on it.  Hardware capabilities are secure and cannot be forged.

AS I have remarked in another article, there are two general styles of
capability implementation, those that keep capabilities in a segment,
and those that mingle them with use data. Either style may be
implemented in sw or hw, and actually capability segments are quite
popular even with hw solutions.

With capability segments, as long as you have a suitable MMU, hw or sw
does not matter; otherwise it does, because the hw solution is to tag
each word of memory with a bit, the sw solution si to tag each
capability with a random key (encrypted), which, as you say, might be
guessed.
--
Piercarlo Grandi, Dept of CS, PC/UW@Aberystwyth <pcg@aber.ac.uk>
  E l'italiano cantava, cantava. E le sue disperate invocazioni giunsero
  alle orecchie del suo divino protettore, il dio della barzelletta