all rights reserved
*******************
d e m o s r e f e r e n c e m a n u a l
by
graham birtwistle
computer science, university of bradford
{ Now Leeds University by way of University of Calgary }
copyright (c) january 1979 by g.m.birtwistle. all
rights reserved. this manual, or parts thereof,
may not be reproduced in any form without written
permission from the author.
it is made available on the strict
understanding that it must not be shown or made
available in any way to p.r.hills, or to any
employee of p.r.hills, or to any employer of
p.r.hills, or to anyone co-operating with him.
the demos system was implemented and tested on the leeds university centre for computer studies dec system 10 computer using the excellent simula compiler written by the swedish defence research establishment, stockholm. in addition, the demos text book and this manual were produced on the leeds machine by the author using the dec utilities sos and runoff.
the author is extremely grateful to the leeds university centre for computer studies for permission to use their computer, and would also like to record his appreciation of the centre's staff for their cheerful, able, and willing assistance over the years.
this implementation of demos follows the demos text ]1[ except on three points:
1) deadlock checking is not yet implemented.
2) the check when an entity becomes terminated to see that it does not hold any resources is not yet implemented. when it is, a tighter check will be made inside r.release(n) ]ref(res)r;[.
n.b. 1) and 2) will be implemented together.
3) in the first implementation - for the demos text ]1[ - entities acquiring resources from reses or bins, or coopting entities from waitqs, were not entered into the appropriate queue if the request could be accommodated at once. it would seem to be more consistent if they are and so that implementation detail has been altered. as far as the examples in ]1[ are concerned, the practical effect is noticable only on the statistic qmax which may be as reported in ]1[ or 1 greater.