Implement a very basic file system, as discussed in class.

Make sure you create programmer-friendly functions for all
the necessary options. Even though we want an interactive
environment for user controlled testing, the ultimate aim
is to make a useful system that provides something like the
functionality of the unix calls open(), read(), write(),
close(), etc. for use in programs.

Necessary operations:

  Initialise the file system, getting a new disc ready for 
     use, or clearing an old disc that is full of rubbish.

  List all useful information in the root directory.

  Search the root directory, retrieving the information for
     a particular file.

  Create a new file. It is acceptable at this stage to
     insist that the file's contents come from a real unix
     file (magnetic tape) at the time of creation.

  Retrieve and show the contents of a file.

  Delete a file - just mark it as non-existent.

The functions and data structures, and how to operate your
program must be documented sufficiently that we can tell how
to try it out before making a detailed inspection of your
code.

Recommendation: make a convenience function something
like tape_to_disc(tape_file_name, disc_file_name) that
does all the work of creating a disc file that is an
exact copy of a "magnetic tape" file, and another one
that does the opposite: copy a disc file exactly to
tape. Those functions will help to test your essential
functions, and could be very useful in the future.

Provide a very basic interactive interface to your program,
allowing the user to select which operation is to be performed
and to provide file names etc. This does not need to be fancy,
just usable. Perhaps offer the user a menu of things to do.

The deadline for this is short because it is mostly just
putting together the demonstrations you saw in class, to
get you safely started with something practical.

Include in your submission a transcript (the unix "script"
command is good for that) of a test run.