
The three programs included print out the name of all files in the current folder
         and all sub-folders.

r1:   Uses recursion, changes folders as it works, is the smallest code, slowest,
         and uses most memory.

r2:   Uses recursion, does not change folders while it works, is medium size and speed.

r3:   Does not use recursion or change folders, is the largest and fastest, and
          uses the least amount of memory while working.


And finally, a useful program.

r4:   A routine written so you can call it repeatedly to get the next file name whenever
          you need it.  The example program just prints out the file name, but you could do
          anything you wanted with the return.