GNU Octave - GNU Octave is a programming language for scientific computing.

MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming

C++ - Has imperative, object-oriented and generic programming features, while also providing the facilities for low level memory manipulation

LTspice - LTspice® is a high performance SPICE simulation software, schematic capture and waveform viewer with enhancements and models for easing the simulation of analog circuits.

D (Programming Language) - D is a language with C-like syntax and static typing.

MapleSim - MapleSim is an advanced system-level modeling tool that enables innovation and reduces development risk.