All machine problems and homeworks in CS 241 will be submitted through a version repository system called subversion, often abbreviated SVN. SVN is commonly used as part of open source products, used at a number of large corporations, and is one of the most widely used open-source version control system available today. If you're interested in finding out more about SVN, the Wikipedia article is a good start.
There are a wide number of SVN clients on the Internet. The only client that will be officially supported by the CS 241 staff is the command line svn client provided on the linux.ews.illinois.edu boxes. However, absolutely any client that "speaks" svn should work.