Updated and added the example for asynchronous communications.
Added an example for writing to a file.
Added a program to read the binary file created in the file writing example.
Deleted the binary file and added the source for the file to check the data file.
Deleted the executable file
Added more files to remove in the makefile. Changed the reference to one of the listing.
Added a 'todo' marker for things in the text that need to be done.
Added the introductory paragraphs to the communications chapter.