PostScript

PostScript. It is a page description language and a Turing-complete programming language developed by Adobe Inc. founders John Warnock and Charles Geschke. First released in 1984, it revolutionized desktop publishing by enabling device-independent, high-quality text and graphics printing. The language's core model uses a stack-oriented programming paradigm to describe the appearance of text, vector graphics, and raster images on a printed page.

History

The development originated from projects at Xerox PARC, including the InterPress language. Dissatisfied with Xerox's commercialization strategy, Warnock and Geschke founded Adobe Systems in 1982. The first major implementation was the Apple LaserWriter, introduced in 1985, which brought WYSIWYG publishing to the Macintosh platform. This was famously demonstrated by Aldus Corporation's PageMaker software, igniting the desktop publishing revolution. Subsequent versions, including PostScript Level 2 in 1991 and PostScript 3 in 1997, added features like improved color separation, support for JPEG and PDF, and better font handling.

Language overview

As a stack-oriented programming language, it uses reverse Polish notation for its operations. Fundamental graphics operators construct paths using Bézier curves, which are then stroked or filled. The language treats outline fonts, such as those in the Adobe Type 1 format, as specialized graphics programs, enabling sharp rendering at any resolution. Its device-independent nature relies on an abstract imaging model that interpreters translate for specific output devices like laser printers or imagesetters. Key concepts include the graphics state, controlled by operators like `gsave` and `grestore`, and the use of dictionaries for name lookup and variable storage.

PostScript printers and interpreters

Early adopters included printer manufacturers like Apple Inc., Linotype, and Alps Electric. The interpreter, often implemented in firmware using a RISC processor like the AMD 29000, became a standard component of high-end laser printers. The Ghostscript project, initiated by L. Peter Deutsch, created a widely used free software interpreter for viewing and converting files. On-screen rendering was enabled by Display PostScript, used in systems like NeXTSTEP and some versions of Sun Microsystems' OpenWindows. The language's computational power was also leveraged in scientific visualization and even demoscene productions.

Use in printing and publishing

It became the de facto standard for professional prepress and commercial printing, driving the adoption of digital typesetting. The language's precision was essential for color separation in CMYK printing workflows, as used by QuarkXPress and Adobe InDesign. Service bureaus relied on Raster Image Processors from companies like Scitex and Screen Holdings to produce film for offset printing. Its ability to embed EPS files allowed for the reliable exchange of illustrations created in Adobe Illustrator or CorelDRAW. Even as PDF gained dominance, many print workflows continued to rely on it as a final, reliable output format.

Related technologies and successors

The most direct successor is the Portable Document Format, which Adobe derived from its imaging model but designed for efficient viewing and interchange. Display PostScript influenced the development of window system graphics, with concepts appearing in Quartz (graphics layer) for macOS. The XML Paper Specification from Microsoft incorporated similar vector graphics principles. In the realm of fonts, the OpenType format superseded Adobe Type 1, while SVG adopted a XML-based syntax for describing vector graphics on the World Wide Web. The underlying Adobe Imaging Model continues to influence modern graphics systems and standards.

Category:Page description languages Category:Adobe Inc. software Category:Desktop publishing