Hi,
  this actually belongs to a thread in comp.lang.oberon.

As I do not know how to post to a newsgroup I send this to the BB  
community. Perhaps someone can forward it to comp.lang.oberon in case  
others there might be interested.

Here are three different implementations of the Eratosthenes algorithm  
(its a zip file containing the 3 programmes in standard blackbox encoding;  
just open them in BB and decode them afterwards); one is using an array of  
set, another one using an array of boolean and a third one - in fact the  
fastest of these three - using a different algorithm.
If you can't figure this one out I can send you a description, but I guess  
it isn't too difficult.
As my students aren't too good at english, the designator names are  
'german', but you probably
can translate them for your purposes.
The 3rd programme is an interesting example of the fact that finding a  
good algorithm still is
superior to buying a faster machine (this can be shown even better with  
the classical greatest-
common-divisor problem).

(Can somebody tell me how to post to a newsgroup?)

Regards

Harro von Lavergne