Especially engineering and technical people out there, you might have used MATLAB. How did you get it?? Bought it?? Commercial version costs $1900. Even the student version costs $99. Or got it pirated? Well it's not good either..
Here's the alternative: GNU Octave. It's more than just alternative. Good thing is that it is fully MATLAB compatible, that means every code written for MATLAB also runs in Octave.
GNU Octave's web address: http://www.octave.org/