SPICE (Simulator Program with Integrated Circuit Emphasis) is a widely used analog electronics circuit simulator. SPICE is a circuit simulation program which converts a text netlist of electrical elements like resistors, capacitors, diodes, transistors and voltage/current sources and their connections to equations to be solved.
Although SPICE is intended by the industry as a way to verify circuit operation at the transistor level before committing to integrated circuit (IC) manufacturing, it is also useful as a learning tool. One popular SPICE simulator is LTspice, which is a freeware electrical simulator from Linear Technology. It is a good tool to demonstrate and observe circuit behaviour before prototyping on breadboards.