In simple terms, PDF and PostScript are file formats which encapsulate both graphics and text elements. Where many people will spot the difference comes with viewing on screen, because PDF files can be looked at using a standard bit of software, such Adobe Reader or Apple's Preview, but PostScript is more difficult, requiring a 'container' such as EPS for previewing purposes.

Nonetheless, there's an easy way to describe the difference in these formats. Where PDF is a portable document format, PostScript is actually a page description, or programming, language which uses a variety of control statements and conditionals, such as variables, defining procedures and looping.

PDF files are more predictable than PostScript. They are easy to view in page format because they don't contain programming constraints, and they also contain built-in compression capabilities so that common file formats like LZW, JPG and ZIP can be used to produce smaller documents.

We tend to take PostScript and PDF for granted when we output files

PDF is an open standard which takes on board everything within a document that's needed to display it, including embedded fonts, text and vector and bitmap graphics. Within the format is a subset of PostScript, with a storage structure that lets all elements to be contained into a single file with options for manipulating data to reduce size where a lower resolution view is all that's needed.

Those who are long in tooth will probably remember early desktop printers which couldn't handle EPS, so all that came out was reams of code. This is because, back in those days, a raster image processor was needed to transcribe the code and turn it into the necessary dots for subsequent printing, or film and plate making. It became a standard format for handling the import and export of PostScript files and was device-independent, which added to its usefulness.

EPS format can be used to preview PostScript 'information' in programs which don't have a built-in RIP. The PDF format hasn't superseded PostScript, but it has simplified the method in which the data can be viewed as an alternative to EPS. It's also considerably more practical than EPS as PDF can accommodate a whole host of additional information as well as the fonts and graphics within the file. Its ability to contain instructions for printing, job tickets and hyperlinks makes it extremely flexible in a variety of environments.

Today, we take the generation of a PDF file as a given. We use the format widely, from printing boarding passes, generating proofs and newsletters, to using PostScript algorithms to produce high-quality final output. PDF is now clever enough to work out what's non-PostScript information and manage to render it as suitable for viewing and printing. It's all clever stuff.