PostScript is an interpreted language, which means that there is no compiler for it. An interpreter is like a compiler that, instead of producing a sequence of actions in machine language for the computer to handle at some future time, performs the actions itself immediately.
Most interpreters are also previewers, which allow you to view the PostScript drawing as it is created by the PostScript program. Unfortunately , viewing the document on-line is not guaranteed to be a perfect simulation of printing the document. Complex programs that use random numbers or check the device type will almost certainly run differently.
Some interpreters are meant for looking at text documents without printing them. They usually have a number of functions for flipping back and forth between pages. These interpreters are called document previewers.
Below are some of the interpreters available :