SPICE is a powerful circuit simulation
program that was created by the University of California-Berkeley
under contract from the US Government way back in the early 1980s.
This is how you use SPICE:
- On a sheet of graph paper, draw out the circuit that you want to simulate.
- Put a number next to each connector. That is, if you have a voltage source tied to a resistor and a capacitor in parallel, then the T-shaped lead that connects the three units receives a number.
- Open a basic text editor on your computer.
- For each component in your circuit, write down the connector number that is attached to each lead of the component. So a resistor would have two numbers written down, a transistor would have three, an op-amp would have five, etc. The set of lines you have are called a netlist.
- Run SPICE on your netlist. You will get an output file that gives the voltage at your specified output node over a range of voltages at your specified input node. You can also do frequency analysis on your circuit.
The terms of the contract were that once Berkeley was finished with the job, SPICE would be made publically available for free. However, the university was not required to provide support for the product. This led to the creation of several start-ups devoted to selling their own brand of SPICE, and making money off of writing better instruction manuals or providing better tech support. As a further competetive step, some companies released their own distributions of spice that were geared towards Integrated Circuit design, or power supplies, or that put a GUI on the original product, especailly at the tricky circuit design step.
I find the history of SPICE relevant, in that it seems to model the current state of the industry in linux distributions today: A number of companies trying to make money off of free software.
Also, it should be added to N-Wing's writeup that the spice from Arrakis can have disturbing mutagenic properties, when taken in large enough quantity.