Peter.....
> Under Linux and PostgreSQL I expected to create a single database file
> that I then would write code to access.....
You don't access the file, you access the postgresql server, it takes care
of storing the data transparently, some in memory, some on disk. The
language I use to talk to the database server (the postmaster, I think
it's called) is perl or php, C is also common. Each language has a
prewritten library of functions to insert, update, delete, etc., etc.
> I heard that pg_dump may have created a file but again I can't seem to
> find this file anywhere.....
Pg_dump dumps all the data out in ascii format as it stands at one point
in time, you use it for making a back up of the database or transporting
it to another database server.
brew