Mark Wai writes:

>Based on my own experience, I agreed.  It was not easy for me(VM
>implementation newbie) to go through this interp.c due to the modulation
>issue that Dick mentioned.  When I study the VM code in Pocket Smalltalk,
>quite honestly, it is much easier for me to follow and understand (the VM
>source is divided into 8  logical components -- GC, memory, etc).  I guess
>partly is the fact that Pocket Smalltalk is much smaller -- but its small
>size also help me to grasp the core concepts and implementation faster.

Please understand that interp.c is NOT source code -- its OBJECT 
code, translated to C from the interpreter source codes. 
Accordingly, its no surprise that you would find the code unreadable 
-- in the form you are reading it, it has already had comments 
cleared, inlines inserted and details munged.

The source code is written in Smalltalk, not C, and is available 
under Squeak in the several classes in category Squeak-Interpreter, 
and it is beautiful to behold.  Understanding this is fundamental to 
understanding Squeak's core design principles.  More can be gleaned 
on this point from the excellent "Back to the Future" article, 
available at the Squeak web site.

That's where you should begin your inquiry.