PostScript is a programming language for describing the appearance of a printed page. Rather than sending a printer a fixed grid of dots, a program emits PostScript code that tells the output device how to construct the page: where to place text, how to draw curves and fills, and how to position scanned images. The device-resident interpreter then renders, or “rasterizes,” those instructions into the dots the engine actually marks on paper. Adobe’s own PostScript Language Reference, the authoritative manual known informally as the “red book,” documents the language syntax, the Adobe imaging model, and the behavior of the graphics operators that make up the language.
The language was Adobe’s first product. The Computer History Museum, which released an early version of the PostScript source code in 2022 with Adobe’s permission, dates the public launch of PostScript to 1984 and describes it as the technology that “became an essential ingredient in the desktop publishing industry, accelerating computing’s transformation of printing.” Adobe cofounder John Warnock led the team that built it, drawing on work the founders had begun at Xerox PARC on a page-description system called Interpress before leaving to start Adobe in 1982.
Technically, PostScript is a stack-based, interpreted language in the same broad family as Forth. Operands are pushed onto an operand stack and operators consume them; the expression “100 200 moveto” pushes two coordinates and then invokes the moveto operator. The language is Turing-complete, with variables, procedures, conditionals, and loops, which means a PostScript program is genuinely a program and not merely a static data file. This generality let typesetting software express arbitrarily complex layouts, but it also meant rendering a page could require real computation inside the printer.
A central part of PostScript’s value was its treatment of type. Fonts are described as outlines, mathematical curves that can be scaled to any size and rotated or skewed without the jagged edges of bitmap fonts. The same outline that produces crisp ten-point text on a 300-dot-per-inch office printer produces equally crisp output on a high-resolution imagesetter, because resolution is the device’s concern, not the document’s. This device independence, combined with high-quality typography, is what made professional-looking documents achievable from a desktop computer.
PostScript reached the market in 1985 inside the Apple LaserWriter, which paired the interpreter with a laser print engine and AppleTalk networking. Together with the Macintosh and Aldus PageMaker, the LaserWriter launched the desktop publishing revolution. PostScript went on to become the standard imaging language of the professional printing industry for decades, and it served as the direct technical ancestor of PDF, the fixed-layout document format Adobe derived from it in the 1990s.