Poisson.* is an S-Basic program designed to work in the extended
range. Like Binomial.* it is written making use of logarithms.
The same procedure is used to find out the number of good digits
in the answer. # good = 5 - #of digits in characteristic - # of
iterations of X. 
     The Poisson distribution is used where the mean number of
events is know (on the average 158.394 telephone calls come in an
hour at a certain buisness, what is the probability only 23
coming in an hour on a certain day?) Mean = lambda = 158.394;
number of occurances (must be integer) = 23. Logprob =
-40.6081... ; probability = 2.46E-41. Note that this program will
work for Probabliity < 1E-128. For instance  if we have a poisson
process with X = 452, Lambda = 35.612; we wind up with a
proability = 2.03 E -320. This is reported as 2.03 Ten -320 by
the progrem. A Nevada Basic version of the program is available
on this disk. This program was written by
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                          Michael P Finerty
                        2358 E Parkside Drive
                        Tucson, Arizona 85713