What is "scilab"

Scilab is an open source, cross-platform numerical computational package and a high-level, numerically oriented programming language. It can be used for signal processing, statistical analysis, image enhancement, fluid dynamics simulations, numerical optimization, and modeling, simulation of explicit and implicit dynamical systems and (if the corresponding toolbox is installed) symbolic manipulations.

Scilab is one of the two major open-source alternatives to MATLAB, the other one being GNU Octave. Scilab is similar enough to MATLAB that some book authors (who use it) argue that it is easy to transfer skills between the two systems. Scilab however puts less emphasis on (bidirectional) syntactic compatibility with MATLAB than Octave does.