Question : post script files?

what are post script files,difference between postscript and PDF files.How to open PS files.what are post script printers?
Any one having full answer ? detailed answer preffered.

Answer : post script files?

PostScript is a language designed originally by Adobe.  The idea is, as with other printer languages, that instead of simply sending an image to the printer, you send a description of what you want, and the printer then interprets that description and prints the page.  This is extremely efficient (in terms of the amount of data sent down the wire) for printing text documents or line drawings rather than graphics.  So basically PostScript is a programming language which is interpreted by PostScript printers.  It's fairly similar to the FORTH language.

To print a circle with a caption to an normal, dumb, image-data-based printer, you would send the raw data to the printer in a similar way that it's sent to a screen, by plotting each pixel one at a time.  To print it to a postscript printer, you send it a description of the circle (e.g. centre, radius, line thickness) and a description of the caption (e.g. the words, origin, which font, size.)  The printer itself understands the PostScript definition and draws the circle and the caption based on the descriptions.  This is rather over simplified; to see some real PostScript programs, see the examples from the Blue Book (the most famous book on how to program in PostScript) here:

http://www.wins.uva.nl/~robbert/ps/

A PostScript printer is any printer which can directly interpret the PostScript language.  They typically have a fairly fast processor and large memory, and store a very wide range of fonts "on board" so that you don't have to send font definitions to them.  Some of them are more powerful than entry-level desktop computers.  They are typically used in organisations which do a lot of document printing and don't want to tie up their networks.  There are other standards for similar printer languages, such as HPGL (Hewlett Packard Graphics Language) and other proprietary standards.

PDF is different from PostScript mainly because of the "Portable" bit of "Portable Document Format."  It is less efficient than PostScript, because it captures all the details of the fonts used in the document, the formatting, the colours, etc. (see http://www.adobe.com/prodindex/acrobat/adobepdf.html for a more full basic description.)  It therefore is pretty much guaranteed to view and print the same on every single platform.  You may not find this with PostScript -- for example, the PostScript printer which was used to produce the original document may have a different set of fonts from the one you're using.

PostScript, also, is hugely more powerful, as it is a true programming language.  I've seen someone write a fractal generator in pure postscript which was only half a page long, but produced a 600dpi page print of a section of the Mandelbrot set, after the printer had actually done all the maths to calculate it.  That should give you a fair idea of the benefits of using a PostScript printer if your software is optimised to produce it.

PostScript, being originally intended for use solely by powerful printers, is normally quite difficult and processor-intensive to view, and requires specialist programs, the most famous of these being GhostScript, used originally on Unix platforms.  GhostScript is basically a software PostScript interpreter/viewer; a program for your computer that "pretends" to be a PostScript printer, but outputs to the screen instead of paper.  There is a Windows version called Aladdin Ghostscript, see:

http://www.cs.wisc.edu/~ghost/aladdin/get550.html

for how to obtain it.

Hope that answers your question!