PostScript

PostScript describes the appearance of a page by combining programming instructions with a precise imaging model. Rather than storing a page as a fixed bitmap, a PostScript file can specify paths, transformations, colors, text, and sampled images that a printer interprets at its own resolution. The language is stack-based: operands are placed on stacks and operators consume them, a design influenced by earlier interpreted languages and well suited to compact page descriptions.

A PostScript interpreter converts these instructions into marks through a raster image processor, or RIP. Its coordinate system, Bézier curves, clipping paths, compositing operations, and device-independent color concepts allow the same description to target screensetter film, laser printers, and other output devices. The language is also computationally expressive, so a file may contain variables, procedures, loops, and conditionals rather than merely a sequence of drawing commands.¹

PostScript helped establish the technical basis of desktop publishing by linking personal computers, page-layout software, and high-resolution printers. Adobe created the language in the early 1980s, drawing on work associated with Xerox PARC; Apple’s 1985 LaserWriter made it widely visible by pairing PostScript with the Macintosh and the emerging desktop-publishing market. Programs such as Aldus PageMaker and professional typesetting systems could send one sophisticated description to many compatible devices.

Adobe released successive revisions, including Level 2 in 1991 and PostScript 3 in 1997. These revisions expanded color handling, image compression, font support, forms, and performance features. PostScript Type 1 fonts became especially important in digital typography because their outlines were represented mathematically and could be rasterized at different sizes, although later font technologies and licensing changes reduced their centrality.

PostScript files commonly contain a header, setup procedures, page descriptions, and a trailer, while the Document Structuring Conventions provide comments that help applications identify pages, bounding boxes, fonts, and other resources. Encapsulated PostScript, or EPS, is a restricted form intended to embed a single illustration inside another document; it normally includes a bounding box and may include a preview image.

PostScript’s imaging model separates description from output hardware, but successful production still depends on fonts, printer memory, color management, and interpreter behavior. A RIP executes the program, resolves resources, and rasterizes the result; errors such as stack underflow, undefined operators, or missing fonts can therefore appear only at output time. Ghostscript is a widely used interpreter and converter that supports PostScript and related formats, illustrating the language’s continuing role in software pipelines.¹ The Library of Congress identifies PostScript as a significant digital format for page description and prepress exchange.²

PostScript is a full programming language, not merely a markup notation, and that flexibility explains both its power and some of its operational risks. A document can define procedures, generate artwork algorithmically, inspect interpreter state, and interact with resources; printer administrators have consequently treated untrusted PostScript more cautiously than passive image files.

Display PostScript extended the model to interactive computer displays, while printer PostScript emphasized predictable page output. PDF adopted important ideas from PostScript, including paths, graphics state, and imaging concepts, but it is a structured document format rather than a general program interpreted in the same way. PostScript also survives in specialized niches: archival and prepress systems, font and graphics testing, education, and conversion tools. Its historical importance is therefore broader than the number of new printers that directly accept it.

RIP

Raster image processor; software or hardware that interprets a page description and converts it into pixels or printer marks.

EPS

Encapsulated PostScript, a constrained PostScript file format commonly used for single-page illustrations and embedded graphics.

Imaging model

The rules governing coordinates, paths, text, color, clipping, and other operations used to construct a rendered page.

Document Structuring Conventions

Comments and conventions that organize PostScript files for applications such as page extraction, previewing, and printing.

PostScript Type 1

A vector-font technology historically associated with PostScript and desktop publishing.