Re: Bug in acroread?
On Tue, Mar 13, 2007 at 01:02:17PM +0100, Florian Kulzer wrote:
> On Tue, Mar 13, 2007 at 12:51:09 +0100, Joe Hart wrote:
[...]
> > Is postscript so bad that everyone needs pdf? No. The fact that PDF
> > files are hard to edit is what makes them so popular in the business world.
>
> I think it was mostly the PDF compression which made it more attractive
> than postscript as a format to exchange documents via the internet.
The compression was a small part of it. A much larger part of the advantage
of PDF is that while PostScript is a full, Turing-complete programming
language with functions for filesystem access and the like in addition to
page definition functions, PDF is just a page definition language.
This limits various security issues in documents, including malicious code
causing security breaches (imagine a PS file that, when viewed, reads
/etc/passwd and appends it to itself with the current IP address so that it
eventually gets back to the sender as it gets passed around) and DoS
attacks (all it takes is an infinite loop). It also makes writing an
interpreter for the format significantly simpler. (It may also make
rendering faster; for example, the same JPEG compression PDF uses can be
implemented with PS code, but it will execute faster if it is implemented
as part of the interpreter itself.)
(By the way, I don't mean to suggest that being a Turing-complete language
makes PostScript bad in some way, just not as suitable for passing
documents around. PS is a fun language and I recommend learning it. It's
stack-based, which makes working with it a useful exercise in thinking in
unfamiliar ways. You can get around some of it by setting variables, but
the requirement for dictionaries with explicitly declared sizes makes it
both more efficient and more entertaining to learn to use the stack well.)
> Regards,
> Florian
--Greg
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