| PostScript is both a programming language, equipped with powerful graphics capabilities, and a page description language. Its main purpose is to describe the appearance of text, graphics and images on a page, and to communicate this description to a raster-output printing device. PostScript language page description is device independent. This means that any page described by the PostScript language can be produced on any device equipped with a PostScript interpreter. The interpreter translates the PostScript data into a raster of printing dots which are imaged on an output device, such as a laser printer or imagesetter.
Device independence may be PostScript's single most significant feature in that it affords cross-system file compatibility to a broad range of output devices. As a printing model, PostScript describes in detail each element of the page, down to the pixel level, so that the output device, or printer, can print the pixels on the page. The number of dots or lines per inch available to the printer determines the printing resolution of the page. Because the same PostScript data can be sent to output devices of different imaging capabilities, PostScript is said to be resolution-independent as well as device-independent.
There are certain limitations and compatibility problems in the PostScript language. Such compatibility conflicts can be caused for example, by a PostScript interpreter, running on a specific processor, in a specific operating environment. If such problems are encountered, the PostScript program cannot be executed by the interpreter, and a PostScript error will be generated. Sometimes, PostScript language files can be edited and problems corrected.
The accuracy of the reproduction depends upon a number of factors. These include resolution (the number of pixels, measured in dots per inch, which the output device is capable of reproducing) and addressability, or the degree of accuracy of the output device in sizing and placing the individual dots. |
