Ngspice is the name of a project and of a program in the project.
 Spice is the famous circuit simulator developed by the CAD Group of
 the University of California at Berkeley (UCB). The NG prefix has a
 lot of meanings: Next Generation, New Good, etc. Choose or invent the
 one you prefer. The ngspice project aims to improve the capabilities
 of the Spice3 circuit simulator. The heart of the project is the
 ngspice program, a circuit simulator derived from spice3f5.

WWW: http://ngspice.sourceforge.net/