I strongly recommend that you use Matlab or something similar for this class. If you absolutely want to use another language, I will not stop you, but you do it at your own risk. It is easier and much faster to write and debug code in Matlab than in C or Fortran. The nice array syntax allows to write elegant and very readable code.
You can use Matlab, Octave or Scilab. Octave and Scilab are mostly compatible with Matlab and they are free and opensource.
Matlab and Octave are also available in the Math Department Computer lab.
The University Bookstore sells Matlab and I believe you can also buy it online directly from the Mathworks website. They carry a student license which costs around $100 and that includes Matlab plus several commonly used toolboxes. Matlab is available for Windows, Mac and Linux.
Octave is an open source clone of Matlab. All assignments for this class can be written in Octave and the vast majority of the reference Matlab code that will be provided should run unchanged on Octave (version 3.0 or higher is recommended). This is free software that you can download here:
/Applications/Octave.app/Contents/Resources/bin/octave
Scilab is similar to Matlab, however there are significant differences in the syntax (see the Scilab FAQ), so the code I will provide will not run out of the box in Scilab. The required modifications to port Matlab code into Scilab should be minimal (changing comments and the like). Unfortunately I cannot assist you with this, as I am not as familiar with Scilab as with Matlab or Octave. You can get Scilab for Windows, Mac or Linux from the Scilab webpage.
Here are some Matlab tutorials:
Here are some advantages and disadvantages of the different packages