QUESTION: What is the difference between PostScript and PDF?
ANSWER: In a very basic sense, PostScript and PDF are similar. Each is a file format that describes text and graphics. However, there are major differences between PostScript and PDF.
For many people, the most important difference between PostScript and PDF is that it's easy for most computer users to view PDF files on the screen, but it's difficult or impossible for most computer users to view PostScript files on the screen. That's because it's easy to obtain good-quality PDF-viewing software free of charge (for example, the Adobe Reader software), but it is not as easy to obtain PostScript-viewing software.
Another difference between PostScript and PDF is that PostScript is a programming language but PDF is not. This difference, while important, is probably meaningful only to you "techies" (i.e., those of you who write computer programs). PostScript is a programming language because it has things called "conditional constructs," "looping constructs," and other things associated with programming languages. PDF does not have these things.
Also — in general — a PDF file that describes a particular document is smaller than a PostScript file that describes the same document. This is important, because smaller files can be handled more efficiently than larger ones (it takes less time to send smaller files across a network; smaller files take up less space on your computer's disk).
You might have noticed that — with the sample PostScript file and sample PDF file shown at www.citationsoftware.com/faqPostScript.htm and www.citationsoftware.com/faqPDF.htm, respectively, the opposite is true: the PostScript file is smaller than the PDF file. However, for real-life files, it's usually not this way.
The structure of PDF files is much more predictable than the structure of PostScript files. This is important in situations where software needs to modify a document or extract information from a document.
And PDF can do lots of things PostScript can't do. PDF files can be viewed on the Web (with the proper software), whereas PostScript files normally cannot. A PDF file can contain links to locations within the same PDF file, within other PDF files, or on the Web; a PostScript file normally does not contain links. A PDF file can function as a data-entry form but a PostScript file cannot. There are lots of other differences, too.
For these reasons and more, PDF has become a replacement for PostScript in many situations.
For additional information about PostScript and PDF, visit www.adobe.com.
See also What is PostScript?
See also What is PDF?