Your copy of the program via hsp. You will find a version of it, named zoo.cpp, on our class account. However that version does not store the tree to a file and retrieve it. You are to complete the outTree and inTree functions. Use it to output the tree to the screen.
Recursion is probably easier than link chasing.
Write outTree to write to a file, echoing to the screen. Check the file. Use the same traversal to write inTree, i.e. to read in the file. See me if you need a hint. Your copy of zoo.cpp via hsp.