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 -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
