The code is of the form subXz.m , subXpY.m , or subXpYz.m, where X is the subject number, Y is the page within that subject that the code might appear and z is a letter (if it appears) that indicates that multiple fragments of code appear in the same page. If the code is of the form subXz.m it means it does not appear in the subject itself, it is relevant however to the material covered in the subject (extra code beyond the notes).
You can retrieve all files if you download tarCS101.tar. This is a tar file. Unzip or similar zip-like archiving programs can deal with this tar file. On an afs machine, first decide where you want to unzip this tar file and then issue the command tar xvf tarCS101.tar
It will create multiple disrectories of the form Sub4, Sub5, etc with M-files in them as needed.