File Storage
You need a place to store files while you are working on them, which we'll call your work space, and a separate backup space so your work is safe.
At the end of each work session, be sure to copy your work to your backup space. Whatever work space you use, create on it a new directory for each assignment and back it up by copying the whole directory to your backup space.
In addition, be sure to save backup copies of your program files every 10 minutes or so in your work space. Then if your computer or development software crashes, or you make a bunch of changes that turn out to be a bad idea, you can recover without having lost much time. In fact, after you have been working for some time on a program, it is a good idea to have several backups of it in your working directory in case you want to recover code you deleted some time ago.
There are several ways of doing this, each with its advantages and disadvantages. Your primary options follow.
Work space
A personal flash drive (or other portable USB memory device) is probably your best option. For this course 50 MB is more than enough, so one of the smallest and least expensive (about $20) is adequate. Of course you can use it for other courses and personal purposes as well. University Windows machines have readily accessible USB ports into which you plug the drive, and then a new "virtual" disk drive will appear in the file system with a drive letter assigned by the operating system. Flash drives are very convenient, particularly when you are working on multiple machines; for example in lab, on a personal machine, on an STC lab machine with a team member, and on an instructor's machine in office hours (all of which might be used in the course of one assignment). They are also easy to loose and sometimes break, so backing up your work somewhere else is strongly advised.
Another option is the c:\Documents and Settings\<your user name>\Desktop directory of the computer you are using. But you can't take this with you and on STC machines these directories are deleted every night, and perhaps more often. So this is really temporary space, which mean you should copy it to two different backup spaces! Do not use the c:\temp directory, for anyone can access that space, and you are responsible for taking reasonable precautions so that others cannot copy your work.
Backup space
Oncourse may well be your best backup option. Select the My Workspace tab (top left) and then the Resources tab (on the left), and then click Add, fill in a title, and click Add again. This creates an empty directory. You can upload files one at a time to this directory by clicking the Add button to the right of the directory, selecting File Upload in the drop down box, browsing for the file, and clicking Add at the bottom.
This is not very convenient, but it is easy to learn and not bad if you only have one or two files to save at the end of your work session (as in the early assignments). But when you have several files, it will be much more convenient to use WebDAV so you can in one step drag-and-drop your entire working directory into one of your Oncourse Resource directories. The Knowledge Base article http://kb.iu.edu/data/araf.html explains two ways of doing this. (Alternatively, you could make a single zip archive of all your working files and upload the zip file.)
A floppy disk is another backup option for Python programs, but they are far too small for Alice programs, and they are not very reliable. They are also much too slow to use as the working space.
If your working space is on a personal computer, of course you can use any standard backup mechanism, such as a flash drive or CD, but if your computer is not a portable you carry around campus, make sure your files are available when you need them, say when you are getting help from an instructor or when working with an assignment team member.
Flash drives are the most convenient storage when seeing an instructor for help. I don't have a floppy or zip drive on my machine.