Interpress

Interpress. It was a pioneering page description language developed by Xerox for its advanced laser printer systems in the late 1970s and early 1980s. Conceived as a device-independent standard for controlling printers and typesetters, it aimed to precisely describe the layout of text and graphics on a printed page. Although it saw limited commercial deployment, its core concepts directly influenced the creation of the far more successful PostScript language from Adobe Systems.

Overview

Interpress was designed as a high-level, stack-based programming language specifically for printing. Its primary function was to provide a complete description of a document's appearance, including fonts, vector graphics, and raster images, in a way that was independent of the specific output device. This allowed a document created on one system to be printed accurately on any printer that supported the Interpress interpreter. The language was a key component of the Xerox Star workstation environment, representing a significant advancement over earlier printer control languages like those used by IBM or Hewlett-Packard. It facilitated the WYSIWYG (What You See Is What You Get) paradigm that was central to the graphical user interface revolution.

Development and history

The development of Interpress began at the Xerox Palo Alto Research Center (PARC) in the late 1970s, led by researchers including William Newman and Robert Sproull. It emerged from the computing environment that also produced the Alto personal computer and the Ethernet networking protocol. The language was formally released by Xerox in 1981 and was implemented on printers such as the Xerox 9700 and the Xerox Star system's associated printers. Despite its technical sophistication, Xerox pursued a proprietary strategy with Interpress, choosing not to license it broadly to other manufacturers. This decision created a market opportunity that was seized by John Warnock and Charles Geschke, former Xerox PARC employees who founded Adobe Systems and used similar concepts to develop the open, licensable PostScript language.

Technical specifications

As a stack-based language, Interpress used a Reverse Polish notation (RPN) syntax for its operations, similar to the Forth programming language. It described pages using a coordinate system and a powerful set of graphics operators for drawing lines, curves, filled shapes, and sampled images. A key innovation was its treatment of text: fonts were defined as outline descriptions, allowing for scaling and rotation, a concept that became fundamental to modern digital typography. The language supported advanced features like clipping paths and compositing operations. Interpress interpreters were implemented in the printers themselves, requiring significant computational resources for the time, which were provided by dedicated microprocessors from companies like Motorola.

Usage and applications

The primary application of Interpress was within the proprietary ecosystem of Xerox's office automation systems. It was the native printing language for the Xerox 8000 series network systems, which included the Xerox Star and later the Xerox ViewPoint software. Documents created in applications like the Xerox Star's word processor or drawing program were translated into Interpress commands for printing on networked devices like the Xerox 4045 laser printer. Its use was almost exclusively confined to high-end corporate and research environments that had invested in the complete Xerox integrated system. Outside of Xerox, it saw minimal adoption, as the company's closed approach prevented its integration with competing systems from Digital Equipment Corporation or emerging IBM PC compatible computers.

Impact and legacy

Although commercially overshadowed, the technical and conceptual legacy of Interpress is profound. It directly demonstrated the feasibility and utility of a device-independent page description language. Key Adobe engineers, including Warnock and Geschke, were intimately familiar with its design, and PostScript can be viewed as its spiritual and technical successor. The commercial triumph of PostScript, especially after its adoption by Apple Inc. for the Apple LaserWriter and by Aldus Corporation for PageMaker, validated the core ideas pioneered by Interpress. Furthermore, the language's advanced graphics model influenced later standards such as the Portable Document Format (PDF), also created by Adobe. In essence, Interpress provided the crucial blueprint for the electronic publishing revolution that transformed industries from printing to design.

Category:Page description languages Category:Xerox Category:File formats Category:Computing history