This is one of six homework assignments assigned by Professor Lowenthal in Brooklyn College's Data Structures class during the Fall 2012 semester. I can't vouch for the quality of the code, and I will note that it's heavily influenced by my experiences with Objective-C, but it's thoroughly commented and should be clean enough.
The point of the assignment is similar to the previous one in that we are practicing with read/write basics. The difference is that we are applying additional processing and business logic the records being read in.
You can see the full assignment in my iCloud Photo Stream, here.
The idea is to read the data in from the transactions file and calculate the balance for each customer in the master file.
It's free for the taking, so use it, don't abuse it.