A brief description of the files in this folder: 

Makefile -- there's only one run-unit in this lab ("bst"), so "make" does it all 
README.txt  -- this file 
bst.cc -- the only file you need to change
lab4.pdf -- the lab write-up (the same as what is linked on the course webpage)
unit.cc -- Unit class definitions (to test bst.cc functions)
unit.h -- Unit class declaration