Adobe Photoshop 1.0 Source Code

The Computer History Museum:

Thomas Knoll, a PhD student in computer vision at the University of Michigan, had written a program in 1987 to display and modify digital images. His brother John, working at the movie visual effects company Industrial Light & Magic, found it useful for editing photos, but it wasn’t intended to be a product. Thomas said, “We developed it originally for our own personal use … it was a lot a fun to do.”

Gradually the program, called “Display”, became more sophisticated. In the summer of 1988 they realized that it indeed could be a credible commercial product. They renamed it “Photoshop” and began to search for a company to distribute it. About 200 copies of version 0.87 were bundled by slide scanner manufacturer Barneyscan as “Barneyscan XP”.

The fate of Photoshop was sealed when Adobe, encouraged by its art director Russell Brown, decided to buy a license to distribute an enhanced version of Photoshop. The deal was finalized in April 1989, and version 1.0 started shipping early in 1990.

Along with the 1.0 source code (mostly Pascal, with some 68K assembler), CHM has PDFs of Adobe’s excellent Photoshop 1.0 User Guide and Tutorial. CHM trustee Grady Booch, chief scientist for software engineering at IBM Research Almaden, on the source code:

There are only a few comments in the version 1.0 source code, most of which are associated with assembly language snippets. That said, the lack of comments is simply not an issue. This code is so literate, so easy to read, that comments might even have gotten in the way. [...] This is the kind of code I aspire to write.

A little birdie who works at Adobe today told me, regarding the lack of comments, “Let me assure you, that trend continued for the next 35 years.”

Jason Snell, at Six Colors, notes:

The only shame is that this release doesn’t include the code from the MacApp applications library, which Photoshop used and is owned by Apple. It would sure be nice if Apple made that code available as well.

Says my little birdie, “Turns out Adobe got a perpetual license to MacApp and a heavily modified version of it is still the basis of the UI code. It is only recently starting to get replaced. Even more crazy is that parts of that MacApp code are running on iOS and Android and the web versions.”

Quite the legacy for what started as a personal project between two brothers.

★ Friday, 19 December 2025