The res device is a two-terminal resistor. Typically, a value property is added to specify resistance. Alternatively, a model property can be added to specify a resistor model. If a model property is assigned, then a param property can be used to supply the geometric or other parameters.
The `+ ' symbol in the representation accesses a branch property that returns a hypertext expression consisting of the voltage across the resistor divided by the resistance in ohms, yielding the current through the resistor. The `O' that follows the resistance is the `ohms' unit specifier, and not an extra zero.