In 1987, Thomas Knoll, a PhD student in computer vision at the University of Michigan, wrote a modest Macintosh application named Display simply to render digital images on his screen. What began as a personal project soon caught the attention of his brother John Knoll, who was working at visual effects company Industrial Light & Magic. John saw immediate practical potential in using the software to edit photographs, transforming a personal side project into an engineering effort that would reshape visual media.
From Personal Tool to Commercial Software
Recognizing the tool's commercial promise by the summer of 1988, the brothers renamed the software Photoshop and began searching for distribution partners. An early version 0.87 saw limited release when slide scanner manufacturer Barneyscan bundled about 200 copies under the name Barneyscan XP. Photoshop's trajectory shifted permanently when Adobe art director Russell Brown advocated for the software, prompting Adobe to acquire a distribution license in April 1989. Photoshop version 1.0 officially began shipping to commercial users in early 1990.
The Architecture of a One-Engineer Engine
Despite its ambitious scope, version 1.0 was constructed by an extraordinarily tiny development team. Thomas Knoll served as the sole engineer for the core application codebase, while John Knoll developed many of the application's underlying image-processing plug-ins. Analysis of the version 1.0.1 codebase reveals a compact system spread across 179 files containing approximately 128,000 lines of code. By line count, roughly 75 percent of the application was written in Pascal, while 15 percent was implemented in Motorola 68000 assembly language to optimize performance-critical calculations on personal computer hardware.
Virtual Memory and Clean Abstraction
To manipulate heavy graphic files on desktop machines of the late 1980s, the application had to overcome severe hardware constraints. The software incorporated explicit abstractions for virtual memory, enabling it to process image data far larger than main memory or display buffers could accommodate. The codebase organized image manipulations through tiled data structures and filter abstractions, cleanly separating user interface logic from pixel-processing algorithms. While version 1.0 contained sophisticated selection tools and file importers, it lacked support for multiple image layers, an architectural addition that arrived later in version 3 in 1994.
A Lasting Foundation for Digital Imagery
Over its first ten years, Photoshop sold more than 3 million copies worldwide. The lean architecture created by a single primary engineer and his brother proved remarkably adaptable, laying a foundation that expanded into modern visual computing and ultimately secured the software's place in the English dictionary as a standard verb.
Cover: AI-generated editorial illustration; not a documentary photograph.
Source: Adobe Photoshop Source Code
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