Understanding PostScript: A Revolutionary Language for Desktop Publishing
In the early 1980s, the world of desktop publishing and graphic design was undergoing a significant transformation. Central to this revolution was the invention of PostScript, a page description language (PDL) that would shape the future of printing and digital publishing. Developed by a team at Adobe Systems, led by John Warnock and Chuck Geschke, PostScript became the foundation for many graphical workflows, from desktop printers to high-end publishing systems.
PostScript (PS) is a dynamically typed, concatenative programming language, designed specifically for creating vector-based graphics and describing the layout of text and images on printed pages. Unlike many programming languages, PostScript doesn’t focus on solving complex computational problems but instead focuses on generating complex visual output—primarily in the form of high-quality print materials.
In this article, we explore the history, features, and enduring impact of PostScript on the printing and publishing industries. We will delve into its syntax, capabilities, and the technological ecosystem that has flourished around it.
Origins and Development of PostScript
The genesis of PostScript can be traced back to the early 1980s when Adobe Systems was still in its infancy. The company was founded by John Warnock and Chuck Geschke, who had previously worked together at Xerox PARC (Palo Alto Research Center), where they were involved in groundbreaking work related to computer graphics and typography. Their vision was to create a language that would allow high-quality graphical output on the newly emerging desktop printers, as well as to facilitate scalable font rendering for high-quality printing.
PostScript’s development began in earnest in 1982, when Warnock and Geschke were joined by a team of engineers at Adobe: Doug Brotz, Ed Taft, and Bill Paxton. Their collective expertise in programming, graphics, and publishing formed the core of the language’s design. The goal was to create a device-independent method for describing printed pages, regardless of the output device used.
Interestingly, PostScript’s syntax shares certain features with Forth, a stack-based language developed by Charles H. Moore in the 1970s. While PostScript was inspired by Forth’s stack-based structure, its internal implementation diverges significantly from Forth’s, focusing instead on graphical rendering and precise control over page layout.
Adobe officially released PostScript to the public in 1984. The timing was serendipitous: it coincided with the rise of the personal computer and laser printer. These two technologies provided a fertile environment for PostScript’s adoption, particularly in the context of desktop publishing.
The Syntax and Structure of PostScript
PostScript is not a traditional programming language in the sense that it does not have loops or conditionals in the way most high-level languages do. Instead, it operates on a stack-based model, which means that data is pushed onto a stack and manipulated according to instructions in the language. Its syntax is heavily influenced by Forth, and its structure is concise, making it suitable for describing complex graphical operations.
In PostScript, commands are executed in a sequence that can include defining variables, creating graphics, and specifying how objects should be placed on the page. While the syntax of PostScript may initially seem foreign, it is relatively simple in its operation. For example, a simple command to draw a line might look like this:
In this example, moveto positions the drawing cursor at the coordinates (100, 100), and lineto draws a line to (200, 200). The command stroke then renders the line on the page.
PostScript’s minimalistic approach is complemented by the ability to define reusable procedures (functions), enabling the creation of complex graphics and page layouts. These functions, called “procedures,” allow for modularity and reuse of code.
Additionally, PostScript supports comments, which can be included using the percent sign (%). These comments are ignored by the interpreter, making them useful for documenting code or providing clarity within a larger script. The inclusion of comments is a key feature for those developing complex PostScript files, as it aids in understanding and troubleshooting the code. However, PostScript does not support semantic indentation—meaning there is no strict requirement on how the code is spaced or aligned, although consistency in formatting is generally encouraged for human readability.
Core Features of PostScript
PostScript is designed with several distinct features that make it particularly suited to the task of page description. These features include:
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Device Independence: One of the defining features of PostScript is its device independence. The language does not depend on the specific characteristics of the printer or display device. This means that a PostScript file generated on a computer can be sent to a variety of printers and still render consistently.
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Vector Graphics: PostScript is primarily used for describing vector-based graphics, which are based on mathematical descriptions of shapes (lines, curves, polygons, etc.) rather than pixel-based (raster) images. This makes it ideal for printing high-quality text and graphics at any resolution.
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Scalable Fonts: PostScript also introduced the concept of scalable fonts, a crucial advancement for desktop publishing. Unlike bitmap fonts, which are fixed at a particular size, scalable fonts can be resized without losing clarity or quality, which allowed for greater flexibility in design.
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Composability: PostScript files can describe entire pages, consisting of both text and graphics, and can easily combine multiple elements. This composability made it a natural fit for publishing applications, where designers needed to assemble complex layouts from multiple graphic and text components.
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Complex Mathematical Operations: PostScript includes a rich set of commands for performing geometric operations, such as scaling, rotating, and translating objects. This allows for precise control over the positioning and transformation of graphic elements on the page.
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Interactive Debugging: PostScript is an interpreted language, which means that files can be modified and tested in real-time, facilitating interactive debugging and adjustments. This feature was particularly helpful for designers who needed to iterate quickly on their layouts.
PostScript in the Desktop Publishing Industry
PostScript’s impact on desktop publishing (DTP) was nothing short of revolutionary. Before its introduction, producing high-quality printed materials was a labor-intensive process that required specialized equipment and expert knowledge. The traditional methods of publishing involved physical typesetting and printing presses, which were both time-consuming and costly.
With the advent of PostScript, designers could now create intricate page layouts directly on their personal computers. PostScript became the lingua franca of the desktop publishing world, enabling the transfer of high-fidelity page layouts between different devices and systems. This was particularly crucial for the emergence of graphic design software such as Adobe Illustrator and Adobe InDesign, which relied on PostScript to output designs to professional printers.
The release of the Apple LaserWriter printer in 1985, which supported PostScript, further cemented the language’s role in the publishing industry. The LaserWriter was the first desktop printer to deliver professional-quality printing and featured PostScript as its core page description language. This printer, combined with the Macintosh computer, provided designers with a powerful and cost-effective solution for producing printed materials, fueling the growth of the desktop publishing industry.
The Legacy of PostScript
Although newer technologies such as PDF (Portable Document Format) and SVG (Scalable Vector Graphics) have emerged in recent years, PostScript remains an important part of the publishing ecosystem. Its influence can still be seen in modern printing workflows, where PostScript files are often used as intermediates in the conversion to other formats.
Furthermore, PostScript has left a lasting legacy in the world of typesetting and vector graphics. Many modern font formats, including TrueType and OpenType, owe their existence to PostScript’s scalable font technology. Similarly, vector-based design software such as Adobe Illustrator and CorelDRAW still rely on the principles of PostScript for generating high-quality graphical content.
PostScript’s simplicity and versatility also paved the way for the development of other page description languages, including PDF. While PDF is essentially a superset of PostScript, it incorporates features that make it more suited for document exchange, such as support for rich media and better handling of compression and encryption. Despite this, the core rendering technology of PostScript lives on within PDF files, underscoring the enduring importance of PostScript in the world of digital publishing.
Conclusion
PostScript is a cornerstone of modern graphic design and desktop publishing. Its development in the early 1980s fundamentally transformed how pages were described and printed, making it an essential tool for the desktop publishing revolution. The language’s flexibility, device independence, and ability to handle high-quality vector graphics made it a natural fit for designers, printers, and publishers alike. Even today, the legacy of PostScript continues to influence the technologies that drive the digital printing and publishing industries.
As we look toward the future of publishing, the principles that underpinned PostScript—the ability to describe pages in a device-independent, scalable, and high-quality manner—will continue to shape the ways in which digital content is created and distributed. Whether through the direct use of PostScript or the evolution of its concepts into modern standards like PDF, PostScript’s impact is undeniable and enduring.
References
- Wikipedia contributors. (2024, December 9). PostScript. Wikipedia. https://en.wikipedia.org/wiki/PostScript
- Adobe Systems. (1984). PostScript: A Page Description Language for Printing. Adobe Press.
- Geschke, C., & Warnock, J. (1997). The History of PostScript. Adobe Systems.