CSCI 587 - Assignment 2 Text Compression

1. The dictionary used by the Unix system command spell is in the file /usr/dict/words. Write a small C program that will calculate the frequencies of each character.
   • What major differences do you see from the frequencies presented in class?
   • Why is this text not a good sample text?
2. Using the Huffman coding encode the phrase "USC wins".
3. Compare the performance of compress, compact, and gzip calculating the compression ratio for each on /usr/dict/words. Also record the time required using the command "time."
   • To do this create a symbolic link to the dictionary from your home directory with the command
     ln -s /usr/dict/words words
   • Then run each of the commands on the file using time using the elapsed time.
     time compact words
     Use the manual ( man 1 time ) to interpret the output.
     u = user time, s = system time, then total or elapsed time.
   • Check the size using the command "wc"
   • You will need to uncompact, uncompress, and guzip to get back to the original file
4. Find a spelling/grammar checker on a PC or Mac.
   • Which wordprocessor are you using?
   • What is the grammar checker's evaluation of
     An hoarse is one thee gulf curse.
     Out the window, the bird flew.
   • How does the spelling checker respond to
     fastly, greenly, et cetera (and I mean the phrase)
5. Extra Credit 3 points A digram is a two character sequence.
   • Using /usr/dict/words calculate a static model for digram compression.
   • For the top ten digrams compute a Huffman code