Course: CS 537
Program: Shared Memory Producer/Consumer Program
Instructor: Barton Miller
Semester: Fall 2018
Lecture: Lec 001
Authors: Zhengqi Liu, Tian Zheng
CS Login: zhengqi, tian
NetID: mliu292, tzheng24

This program runs in parallel on Linux using four threads (pthreads) and 
synchronization for Reader, Munch1, Munch2, and Writer.

This program is divided into two modules.

The main module creates three queues and four pthread threads, passes each thread
its queues to operate on, and waits for threads to finish by calling pthread_join.
It also includes the functions of Reader, Munch1, Munch2, and Writer.
The Reader thread reads from standard input one line at a time, and passes it to
thread Munch1 through a queue.
Munch1 scans the line and replaces each space character with an asterisk ("*") 
character, then passes the line to thread Munch2 through another queue.
Munch2 scans the line and converts all lower case letters to upper case, then 
passes the line to thread Writer though another queue.
Writer writes the line to standard output.

The Queue module includes the functions that handles creating a queue, moving a
location inside a queue, enqueuing a string to the end of a queue, dequeuing a
string from the beginning of a queue, and printing queue statistics.