is computed by generating random points within a square, whose
dimensions are 2 x 2, and checking how many of these
points end up within a circle of radius 1. The ratio of that
number to the total number of points generated by the random number
server should be close to 
for a sufficiently large number of
points.
The program begins by asking the user for required accuracy.
The computation of 
will go on until either the required
accuracy is reached, or until the number of points generated
by the random number server exceeds certain hardwired limit.
The process responsible for writing to the VDU updates the displayed
value of 
every time the results are collected from
the workers.