Computer History Museum shares original Photoshop code

Any user can get a closer look at the original code for Photoshop, which transformed image editing more than 20 years ago


To millions of people around the world, the name Photoshop inspires images of sharks leaping out at helicopters, phony disaster photos, and retouched celebrity shots. Now, the original computer code that started it all is available for inspection.

The Computer History Museum in Mountain View, California recently made the source code of Adobe Photoshop 1.0.1 available as a download for noncommercial use. Originally released for the Macintosh in 1990, Photoshop has become synonymous with sophisticated photo editing (including some creative photo hoaxes).

The original program that would become Photoshop was written in the late 1980s by Thomas Knoll, a PhD student at the University of Michigan. He and his brother John, who worked at Industrial Light and Magic, developed Photoshop into a full-fledged consumer-ready application. The first commercial release from slide scanner maker Barneyscan only sold about 200 copies under the name Barneyscan XP, and came bundled with the company's hardware. Soon after that initial commercial foray, Adobe licensed the rights from the Knolls and released an improved version of the program, Photoshop 1.0.

At its original release, Macworld called Photoshop 1.0 easy to use. "Considering the vast number of features and tools involved," Macworld said. "Adobe has done a good job of keeping things organized and simple."

Almost the entire original program is available in the Computer History Museum's download. The only exception is the MacApp framework, which was licensed from Apple. The Photoshop 1.0.1 download comprises 179 files with about 128,000 lines of code. By comparison, the current version of Photoshop has about 10 million lines, according to Grady Booch, Chief Scientist for Software Engineering at IBM Research Almaden and a trustee of the Computer History Museum.

The Museum says about 75% of the original program was written in Pascal and another 15% is in machine language for the Motorola 68000 processor, the original chip for the Macintosh line. The rest of the source code is made up of various bits of data.

Photoshop's original code has almost no comments, the notes written in the source code files to explain what certain chunks of code are designed to do. "This code is so literate, so easy to read, that comments might even have gotten in the way," Booch said in the CHM's blog post announcing the source code release.

You can download the Photoshop 1.0.1 source files from the Computer History Museum. Photoshop joins the museum's online source code collection that also includes MacPaint, QuickDraw, and the APL\360 programming language.

This story, "Computer History Museum shares original Photoshop code" was originally published by PCWorld.

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