The Plague program
The first three fields are where you enter three
integers: InfectiousTime, ImmuneTime, Rate. These give the time after
the infected individual stops being ill, the time after which they stop
being immune, and the number of individuals newly infected each day by
one sick individual.
To run, enter the integers and click on Setup.
Then click on Next Day for each successive generation.
(See Great Ideas in Computer Science, pages 221 to
224 for more details.)