Ngspice is a code-based mixed-level/mixed-signal circuit simulator. Unlike popular circuit sim- ulators, such as LTSpice that are capable of drawing symbolic objects (schematic captures) to de- scribe circuit topology, ngspice simulated circuits are described as text only inside a file called a netlist.
Modelica is an object-oriented, declarative, multi-domain modeling language for component-oriented modeling of complex systems, e.g., systems containing mechanical, electrical, electronic, hydraulic, thermal, control, electric power or process-oriented subcomponents.
MATLAB is a multi-paradigm numerical computing environment and proprietary programming language developed by MathWorks. MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages.