Circuit simulation is a way of building and testing virtual models of electronic devices. It is usually cheaper and quicker to simulate a design than to build a prototype. MacSpice is like most circuit simulators requires a text-file description of the circuit as input. This netlist is a list of components and the nodes they connect to. Users may prepare netlists with a text editor or derive them from a circuit diagram using a third-party schematic-capture MacSpice then builds a numerical model of the circuit and analyses this command interpreter (shell) is used to specify the types of analyses that are required and how the results should be processed, saved or displayed. The high quality of the MacSpice command interpreter makes the automation of tasks straightforward.
The quality of the results depends on the accuracy of the netlist and the device models used. Within Spice most devices are ideal its resistor for example has just one property resistance. A real resistor has parasitic inductance and capacitance if these have a significant influence on the circuit they must be added explicitly to the netlist.
