CTEC2901 Assignment 2
=====================

P12202749 <p12202749@myemail.dmu.ac.uk>

This program reads in words and definitions from supplied text files and stores
them in a dictionary. Once the words and definitions have been added, the user
can search for any of the words and retrieve it's corresponding definition.

Manifest
--------
.
`-- p12202749/
    |
    |-- README              -- Text file explaining the program and it's usage.
    |
    |-- clist/              -- Circular list data structure that is required by
    |   |-- any.h              the hash table.
    |   |
    |   |-- clist.c
    |   |
    |   |-- clist.h
    |   |
    |   `-- makefile
    |
    |-- d1.txt              -- Text file containing words and definitions to be
    |                          entered into the dictionary.
    |
    |-- d2.txt              -- Text file containing words and definitions to be
    |                          entered into the dictionary.
    |
    |-- d_run.c             -- Executable program that creates an instance of
    |                          the dictionary data structure.
    |
    |-- dictionary.c        -- Implementation file for the dictionary.
    |
    |-- dictionary.h        -- Header file containing the function signatures
    |                          for the dictionary.
    |
    |-- ht/                 -- Adapted hash table data structure that is used
    |   |-- any.h              as the underlying structure of the dictionary.
    |   |
    |   |-- chanined_ht.c
    |   |
    |   |-- ht.h
    |   |
    |   `-- makefile
    |
    `-- makefile            -- A UNIX makefile that contains the instructions
                               to build the dictionary library and program.  

Installation
------------

In order to install the dictionary program, untar the gzipped folder and use
the make command:

  $ tar xzf p12202749.tar.gz
  $ cd p12202749/
  $ make

Usage Instructions
-------------------

The program can be run without providing a text file. This will result in an
empty dictionary:

    $ ./d_run

To populate the dictionary with words and definitions, run the program and
specify the text files that you would like to read into the dictionary:

    $ ./d_run d1.txt d2.txt <file3> ...

> N.B. the arguments are optional. You can add as many (or as little) text
  files as you like.

Once the program is running, you can enter a word to search and if it exists
in the dictionary, the definition will be displayed:

    $ ./d_run d1.txt
    $ aardvark <press enter>

Known Bugs
----------

Currently there are no known bugs.

Implementation notes
--------------------

I have chosen to use and adapt the hash table data structure in order to
implement the dictionary. I believe the hash table is a good choice because it
allows the entry and look-up of values, using keys to identify them. The
look-up can be O(1) performance in the best case scenario. When there are no
collisions in the hash table, the definition can be found instantly using the
key to locate the correct bucket for the definition.

However, the performance can degenerate to O(N) performance if all the entries
hash to a single bucket, but I have constructed a hash function that tries to
mitigate that scenario.

I have selected a table size of 500,000 in order to allow sufficient space for
words and definitions to be entered. Computers have lots of memory these days
so I believe this table size is not a significant waste of memory.