> Bit confusing that's for sure, but technologically 8bit PIC uses registers
> only and have no RAM.

It looks like a duck, it quacks like one...

I certainly don't know any other CPU architecture that has indexed 
access to its registers!

 > For example on AVR you have to load the value of a RAM
> location to a register, then you can make some calculations and then have to
> store it back. In PIC it is not necessary as all RAM location is treated as
> a register therefore there is no difference in between RAM or registers and
> has a direct access to the whole area by every instruction.

The PIC isntruction set technically a mix of 'single-accumulator' and 
'memory-memory' architecture.

>> A static stack is (except for the ban on recursion/reentrancy)
>> completely invisible to the user. And it takes the same amount of RAM as
>> a real data stack.
> 
> Fair enough, I just have a bad feeling on automatic decisions which variable
> is like that. 

Why? C has clear requirements about variables, and (without recursion or 
reentrancy) these can equally be met by a static stack or a real stack 
(and by allocating all variables to unique locations - but takes takes 
more memory).

 > With C18 you can choose if the default storage is auto, static
> or overlay and also can choose that one by one in the source using these
> directives - so I have a better control over it.

Yes, but that is because recursion and reentrancy make sense on 18F 
PICs. Without recursion and reentrancy you (as user/programmer) can't 
tell the difference between a static stack and a real stack.

-- 

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu

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