This is the final version of the crossing problem program.  In the previous week,
we pulled much of the code into separate files so that data structures and
information could be shared more easily between the multiple executables.  This
week, the source code was separated even more to allow for 2 shared resource
problems to be solved in 1 program (more on this later).  More importantly,
however, you will find that the signal and wait functions have been put to
work to manage the shared resources across 70 car and train processes.


Looking over the source code, you will find that the functions used to generate
random numbers have been completely overhauled.  Rather than having each
process attempt to create a unique random number seed, all of the random numbers
are now generated by a single process.  In effect, random numbers are now a
resource created by a single producer and used by several consumers.  I recommend
that you try to understand the crossing problem before looking at the solution
to the random number problem.  Just so you know, there are actually a few problems
with this method that are not immediately obvious.  If you think you spotted one,
feel free to zap me an e-mail.