>  I thought that you're referring to Compiler and friends in the
> 'System-Compiler' system category...  If so, it does involve the parse
> tree, because the Compiler here is the translator from the code you
> type to the objects and the sequence of Squeak bytecode.  Also,
> CCodeGenerator is similar kind; which translates the parse tree to
> equivalent C code.

You are right I will need knowledge of the AST. Is it documented anywhere 
other than in the code ?

>  You could just take a look at the InterpreterSimulator, but it will
> give you a hard time if you don't know the Squeak object types, etc.,
> etc.

Right.

>  On the other hand, the C-compiled VM can be seen as a stack machine
> and 256-way switch surrounded by "while (true) {}".  Reading the Back
> to the Future paper, nuBlue book, the VM's generated C code, and
> corresponding Squeak code has all important info about the stack
> organization, object format, etc. etc.

The VM C source was the first thing I looked at followed by 'interp' and the 
CCodeGenerator. Nice set of mechanisms I am very impressed with Squeak. I 
still do not really fully understand the VM and Compiler levels yet, but hay 
I've only been looking at SmallTalk for four days so far :) Have to look at 
the Literal Frame next and get to understand that.

Many thanks for you time,

Aaron