look at the underlying source code

hi

someone can show me how can i get the source code of a function. Is a S4
class or Method. (I'm not an expert in R environment)
Exactly, Function "ugarchsim" from library (rugarch).
I need to know (in detailed ) how the variance and  mean ecuation of a
arma/garch process are calculated.
With other packages like "fGarch" i used to invoked the function debug ()
and allows me to step into the functions but with ugarchsim i can't use it.

any suggestions are well received