gedit is a simple, easy-to-use text editor with support for syntax highlighting for a variety of programming languages, including Python and Fortran. It is installed by default on most GNOME-based Linux systems, such as Ubuntu, and is included in the Virtual Machine for this class.
Another easy-to-use editor, available from http://www.nedit.org/. NEdit is available for almost all Unix systems, including Linux and Mac OS X; OS X support requires an X Windows server.
XCode is a free integrated development environment available for Mac OS X from Apple at http://developer.apple.com/technologies/tools/xcode.html. It should be more than adequate for the needs of this class.
TextWrangler is another free programmer’s text editor for Mac OS X, available at http://www.barebones.com/products/TextWrangler/.
vi (“Visual Interface”) / vim (“vi iMproved”) is a fast, powerful text editor. Its interface is extremely different from modern editors, and can be difficult to get used to, but vi can offer substantially higher productivity for an experienced user. It is available for all operating systems; see http://www.vim.org/ for downloads and documentation. A command line version of vi is already installed in the class VM.
emacs (“Editing Macros”) is another powerful text editor. Its interface may be slightly easier to get used to than that of vi, but it is still extremely different from modern editors, and is also extremely different from vi. It offers similar productivity benefits to vi. See http://www.gnu.org/software/emacs/ for downloads and documentation. On a Debian or Ubuntu Linux system, such as the class VM, you can install it by typing sudo apt-get install emacs at the command line.