Re: Texas Bank Dumps Antivirus for Whitelisting

["Les Bell" <lesbell () lesbell com au>]

"Rob, grandpa of Ryan, Trevor, Devon & Hannah" <rMslade () shaw ca> wrote:

> >
> So you think interpreted languages would be impossible with a Harvard
> architecture?

And compilers.
<<

Nah. Compilers just read in source code data files, write and read
intermediate data files, and then write out object code data files. The
same for linkers. In the *ix world, it's the "chmod +x" that renders the
machine code executable - or rather, tells the loader to render it
executable.

Interpreters are certainly possible in Harvard architectures. The program
just controls which procedures get called at run-time by a recursive
descent parser, or similar. Javascript certainly wouldn't be a problem, nor
would the Java virtual machine. However, threaded interpreted code like
FORTH would be a bit stickier.

When I first started programming the 80286, it was obvious that OS/2 was
designed to separate code and data, especially with its ring-based
architecture. But since OS/2 Presentation Manager graphics segments
actually are threaded interpretive code - in essence, self-modifying code -
a scheme had to be found to allow a single "object" in memory to be treated
as both code and data. It was done by having two segment descriptors - one
a code segment, one a data segment - pointing to the same segment of
memory. The technique (and the related API) was called "Code Segment
Aliasing".

> >
As far as I know, there were only four HA machines ever built,
and that was before high level languages existed.
<<

The entire Intel 8048/8051 series of microcontrollers are Harvard
architecture, if I remember aright. But I tossed out my data books for
those a couple of decades ago.

Best,

--- Les Bell, RHCE, CISSP
[http://www.lesbell.com.au]
Tel: +61 2 9451 1144
FreeWorldDialup: 800909


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