[https://www.gnu.org/software/octave/ GNU Octave] is a high-level interpreted language, primarily intended for numerical computations. It provides capabilities for the numerical solution of linear and nonlinear problems, and for performing other numerical experiments. It also provides extensive graphics capabilities for data visualization and manipulation. GNU Octave is normally used through its interactive interface ([https://en.wikipedia.org/wiki/Command-line_interface CLI] and [https://en.wikipedia.org/wiki/Graphical_user_interface GUI]), but it can also be used to write non-interactive programs.
The GNU Octave language is quite similar to Matlab so that most programs are easily portable.
The GNU Octave distribution includes a [http://www.octave.org/octave.pdf 1000+ page Texinfo manual]. Access to the complete text of the manual is available via the <code>doc</code> command at the GNU Octave prompt.