first Five lines we are defining the inputs. outputs VDD and load value and conditions..
the last four lines mainly defining there which library model you want to use and
how do you want to see your output graph ...
more like here there is standard pattern of defining our circuit.
Spice is nothing but a written discription of our electronics circuit....
I know some of the good spice based simulators which uses spice based component model / libraries and to simulate the circuits and give the resuls and does the different analysis ....
one such is MultiSIM from EWB ( Electronics work bench Canada) , now this company is taken over by National Instruments (NI). and giving a very good solution with integration of Product LAB View....